Allison Okamura

All Publications

• Learning and generalization in an isometric visuomotor task JOURNAL OF NEUROPHYSIOLOGY Rotella, M. F., Nisky, I., Koehler, M., Rinderknecht, M. D., Bastian, A. J., Okamura, A. M. 2015; 113 (6): 1873-1884

  Abstract

  Adaptation is a prominent feature of the human motor system and has been studied extensively in reaching movements. This study characterizes adaptation and generalization during isometric reaching in which the arm remains stationary and the participant controls a virtual cursor via force applied by the hand. We measured how learning of a visual cursor rotation generalizes across workspace 1) to determine the coordinate system that predominates visual rotation learning, and 2) to ascertain whether mapping type, namely position or velocity control, influences transfer. Participants performed virtual reaches to one of two orthogonal training targets with the applied rotation. In a new workspace, participants reached to a single target, similar to the training target in either hand or joint space. Furthermore, a control experiment measured within-workspace generalization to an orthogonal target. Across position and velocity mappings, learning transferred predominantly in intrinsic (joint) space, although the transfer was incomplete. The velocity mapping resulted in significantly larger aftereffects and broader within-workspace generalization than the position mapping, potentially due to slower peak speeds, longer trial times, greater target overshoot, or other factors. Although we cannot rule out a mixed reference frame in our task, the predominance of intrinsic coding of cursor kinematics in the isometric environment opposes the extrinsic coding of arm kinematics in real reaching but matches the intrinsic coding of dynamics found in prior work. These findings have implications for the design of isometric control systems in human-machine interaction or in rehabilitation when coordinated multi-degree-of-freedom movement is difficult to achieve.

  View details for DOI 10.1152/jn.00255.2014

  View details for Web of Science ID 000350994900016

  View details for PubMedID 25520430

• Controllable Surface Haptics via Particle Jamming and Pneumatics IEEE TRANSACTIONS ON HAPTICS Stanley, A. A., Okamura, A. M. 2015; 8 (1): 20-30

  Abstract

  The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming haptic interface.

  View details for DOI 10.1109/TOH.2015.2391093

  View details for Web of Science ID 000351767000004

  View details for PubMedID 25594980

• 3-D Ultrasound-Guided Robotic Needle Steering in Biological Tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Adebar, T. K., Fletcher, A. E., Okamura, A. M. 2014; 61 (12): 2899-2910

  View details for DOI 10.1109/TBME.2014.2334309

  View details for Web of Science ID 000345501000009

• 3-D ultrasound-guided robotic needle steering in biological tissue. IEEE transactions on bio-medical engineering Adebar, T. K., Fletcher, A. E., Okamura, A. M. 2014; 61 (12): 2899-2910

  Abstract

  Robotic needle steering systems have the potential to greatly improve medical interventions, but they require new methods for medical image guidance. Three-dimensional (3-D) ultrasound is a widely available, low-cost imaging modality that may be used to provide real-time feedback to needle steering robots. Unfortunately, the poor visibility of steerable needles in standard grayscale ultrasound makes automatic segmentation of the needles impractical. A new imaging approach is proposed, in which high-frequency vibration of a steerable needle makes it visible in ultrasound Doppler images. Experiments demonstrate that segmentation from this Doppler data is accurate to within 1-2 mm. An image-guided control algorithm that incorporates the segmentation data as feedback is also described. In experimental tests in ex vivo bovine liver tissue, a robotic needle steering system implementing this control scheme was able to consistently steer a needle tip to a simulated target with an average error of 1.57 mm. Implementation of 3-D ultrasound-guided needle steering in biological tissue represents a significant step toward the clinical application of robotic needle steering.

  View details for DOI 10.1109/TBME.2014.2334309

  View details for PubMedID 25014948

• Uncontrolled manifold analysis of arm joint angle variability during robotic teleoperation and freehand movement of surgeons and novices. IEEE transactions on bio-medical engineering Nisky, I., Hsieh, M. H., Okamura, A. M. 2014; 61 (12): 2869-2881

  Abstract

  Teleoperated robot-assisted surgery (RAS) is used to perform a wide variety of minimally invasive procedures. However, current understanding of the effect of robotic manipulation on the motor coordination of surgeons is limited. Recent studies in human motor control suggest that we optimize hand movement stability and task performance while minimizing control effort and improving robustness to unpredicted disturbances. To achieve this, the variability of joint angles and muscle activations is structured to reduce task-relevant variability and increase task-irrelevant variability. In this study, we determine whether teleoperation of a da Vinci Si surgical system in a nonclinical task of simple planar movements changes this structure of variability in experienced surgeons and novices. To answer this question, we employ the UnControlled manifold analysis that partitions users' joint angle variability into task-irrelevant and task-relevant manifolds. We show that experienced surgeons coordinate their joint angles to stabilize hand movements more than novices, and that the effect of teleoperation depends on experience--experts increase teleoperated stabilization relative to freehand whereas novices decrease it. We suggest that examining users' exploitation of the task-irrelevant manifold for stabilization of hand movements may be applied to: (1) evaluation and optimization of teleoperator design and control parameters, and (2) skill assessment and optimization of training in RAS.

  View details for DOI 10.1109/TBME.2014.2332359

  View details for PubMedID 24967980

• Uncontrolled Manifold Analysis of Arm Joint Angle Variability During Robotic Teleoperation and Freehand Movement of Surgeons and Novices IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Nisky, I., Hsieh, M. H., Okamura, A. M. 2014; 61 (12): 2869-2881

  View details for DOI 10.1109/TBME.2014.2332359

  View details for Web of Science ID 000345501000006

• Cerebellar ataxia impairs modulation of arm stiffness during postural maintenance JOURNAL OF NEUROPHYSIOLOGY Gibo, T. L., Bastian, A. J., Okamura, A. M. 2013; 110 (7): 1611-1620

  Abstract

  Impedance control enables humans to effectively interact with their environment during postural and movement tasks, adjusting the mechanical behavior of their limbs to account for instability. Previous work has shown that people are able to selectively modulate the end-point stiffness of their arms, adjusting for varying directions of environmental disturbances. Behavioral studies also suggest that separate controllers are used for impedance modulation versus joint torque coordination. Here we tested whether people with cerebellar damage have deficits in impedance control. It is known that these individuals have poor motor coordination, which has typically been attributed to deficits in joint torque control. Subjects performed a static postural maintenance task with two different types of directional force perturbations. On average, patients with cerebellar ataxia modified stiffness differentially for the two perturbation conditions, although significantly less than age-matched control subjects. Thus cerebellar damage may impair the ability to modulate arm impedance. Surprisingly, the patients' intact ability to generally alter their limb stiffness during the postural task (albeit less than age-matched control subjects) improved their movement performance in a subsequent tracing task. The transfer of stiffness control from the static to the movement task may be a strategy that can be used by patients to compensate for their motor deficits.

  View details for DOI 10.1152/jn.00294.2013

  View details for Web of Science ID 000325346300015

  View details for PubMedID 23843434

• Predictive Modeling by the Cerebellum Improves Proprioception JOURNAL OF NEUROSCIENCE Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2013; 33 (36): 14301-14306

  Abstract

  Because sensation is delayed, real-time movement control requires not just sensing, but also predicting limb position, a function hypothesized for the cerebellum. Such cerebellar predictions could contribute to perception of limb position (i.e., proprioception), particularly when a person actively moves the limb. Here we show that human cerebellar patients have proprioceptive deficits compared with controls during active movement, but not when the arm is moved passively. Furthermore, when healthy subjects move in a force field with unpredictable dynamics, they have active proprioceptive deficits similar to cerebellar patients. Therefore, muscle activity alone is likely insufficient to enhance proprioception and predictability (i.e., an internal model of the body and environment) is important for active movement to benefit proprioception. We conclude that cerebellar patients have an active proprioceptive deficit consistent with disrupted movement prediction rather than an inability to generally enhance peripheral proprioceptive signals during action and suggest that active proprioceptive deficits should be considered a fundamental cerebellar impairment of clinical importance.

  View details for DOI 10.1523/JNEUROSCI.0784-13.2013

  View details for Web of Science ID 000324165500004

  View details for PubMedID 24005283

• Characterization and Psychophysical Studies of an Air-Jet Lump Display IEEE TRANSACTIONS ON HAPTICS Gwilliam, J. C., Bianchi, M., Su, L. K., Okamura, A. M. 2013; 6 (2): 156-166

  View details for DOI 10.1109/ToH.2012.71

  View details for Web of Science ID 000319877500003

• Coaxial Needle Insertion Assistant With Enhanced Force Feedback IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING De Lorenzo, D., Koseki, Y., De Momi, E., Chinzei, K., Okamura, A. M. 2013; 60 (2): 379-389

  Abstract

  Many medical procedures involving needle insertion into soft tissues, such as anesthesia, biopsy, brachytherapy, and placement of electrodes, are performed without image guidance. In such procedures, haptic detection of changing tissue properties at different depths during needle insertion is important for needle localization and detection of subsurface structures. However, changes in tissue mechanical properties deep inside the tissue are difficult for human operators to sense, because the relatively large friction force between the needle shaft and the surrounding tissue masks the smaller tip forces. A novel robotic coaxial needle insertion assistant, which enhances operator force perception, is presented. This one-degree-of-freedom cable-driven robot provides to the operator a scaled version of the force applied by the needle tip to the tissue, using a novel design and sensors that separate the needle tip force from the shaft friction force. The ability of human operators to use the robot to detect membranes embedded in artificial soft tissue was tested under the conditions of 1) tip force and shaft force feedback, and 2) tip force only feedback. The ratio of successful to unsuccessful membrane detections was significantly higher (up to 50%) when only the needle tip force was provided to the user.

  View details for DOI 10.1109/TBME.2012.2227316

  View details for Web of Science ID 000316809800013

  View details for PubMedID 23193302

• Perception of Springs With Visual and Proprioceptive Motion Cues: Implications for Prosthetics IEEE TRANSACTIONS ON HUMAN-MACHINE SYSTEMS Gurari, N., Kuchenbecker, K. J., Okamura, A. M. 2013; 43 (1): 102-114

  View details for DOI 10.1109/TSMCA.2012.2221038

  View details for Web of Science ID 000317644800010

• Behavior of Tip-Steerable Needles in Ex Vivo and In Vivo Tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Majewicz, A., Marra, S. P., van Vledder, M. G., Lin, M., Choti, M. A., Song, D. Y., Okamura, A. M. 2012; 59 (10): 2705-2715

  Abstract

  Robotic needle steering is a promising technique to improve the effectiveness of needle-based clinical procedures, such as biopsies and ablation, by computer-controlled, curved insertions of needles within solid organs. In this paper, we explore the capabilities, challenges, and clinical relevance of asymmetric-tip needle steering through experiments in ex vivo and in vivo tissue. We evaluate the repeatability of needle insertion in inhomogeneous biological tissue and compare ex vivo and in vivo needle curvature and insertion forces. Steerable needles curved more in kidney than in liver and prostate, likely due to differences in tissue properties. Pre-bent needles produced higher insertion forces in liver and more curvature in vivo than ex vivo. When compared to straight stainless steel needles, steerable needles did not cause a measurable increase in tissue damage and did not exert more force during insertion. The minimum radius of curvature achieved by prebent needles was 5.23 cm in ex vivo tissue, and 10.4 cm in in vivo tissue. The curvatures achieved by bevel tip needles were negligible for in vivo tissue. The minimum radius of curvature for bevel tip needles in ex vivo tissue was 16.4 cm; however, about half of the bevel tip needles had negligible curvatures. We also demonstrate a potential clinical application of needle steering by targeting and ablating overlapping regions of cadaveric canine liver.

  View details for DOI 10.1109/TBME.2012.2204749

  View details for Web of Science ID 000308989000003

  View details for PubMedID 22711767

• Feature detection for haptic exploration with robotic fingers INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Okamura, A. M., Cutkosky, M. R. 2001; 20 (12): 925-938

  View details for Web of Science ID 000174018800001

• Reality-based models for vibration feedback in virtual environments IEEE-ASME TRANSACTIONS ON MECHATRONICS Okamura, A. M., Cutkosky, M. R., Dennerlein, J. T. 2001; 6 (3): 245-252

  View details for Web of Science ID 000171123900005

• M-Width: Stability, noise characterization, and accuracy of rendering virtual mass INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Colonnese, N., Okamura, A. M. 2015; 34 (6): 781-798

  View details for DOI 10.1177/0278364914559294

  View details for Web of Science ID 000353981500004

• Sensory Substitution and Augmentation Using 3-Degree-of-Freedom Skin Deformation Feedback IEEE TRANSACTIONS ON HAPTICS Quek, Z. F., Schorr, S. B., Nisky, I., Provancher, W. R., Okamura, A. M. 2015; 8 (2): 209-221

  Abstract

  During tool-mediated interaction with everyday objects, we experience kinesthetic forces and tactile sensations in the form of vibration and skin deformation at the fingerpad. Fingerpad skin deformation is caused by forces applied tangentially and normally to the fingerpad skin, resulting in tangential and normal skin displacement. We designed a device to convey 3-degree-of-freedom (DoF) force information to the user via skin deformation, and conducted two experiments to determine the devices effectiveness for force-feedback substitution and augmentation. For sensory substitution, participants used 1-DoF and 3-DoF skin deformation feedback to locate a feature in a 3-DoF virtual environment. Participants showed improved precision and shorter completion time when using 3-DoF compared to 1-DoF skin deformation feedback. For sensory augmentation, participants traced a path in space from an initial to a target location, while under guidance from force and/or skin deformation feedback. When force feedback was augmented with skin deformation, participants reduced their path-following error over the cases when force or skin deformation feedback are used separately. We conclude that 3-DoF skin deformation feedback is effective in substituting or augmenting force feedback. Such substitution or augmentation could be used when force feedback is unattainable or attenuated due to device limitations or system instability.

  View details for DOI 10.1109/TOH.2015.2398448

  View details for Web of Science ID 000356521100009

  View details for PubMedID 25647582

• Methods to Segment Hard Inclusions in Soft Tissue During Autonomous Robotic Palpation IEEE TRANSACTIONS ON ROBOTICS Nichols, K. A., Okamura, A. M. 2015; 31 (2): 344-354

  View details for DOI 10.1109/TRO.2015.2402531

  View details for Web of Science ID 000352361300010

• Artificial Tactile Sensing of Position and Slip Speed by Exploiting Geometrical Features IEEE-ASME TRANSACTIONS ON MECHATRONICS Damian, D. D., Newton, T. H., Pfeifer, R., Okamura, A. M. 2015; 20 (1): 263-274

  View details for DOI 10.1109/TMECH.2014.2321680

  View details for Web of Science ID 000352060700026

• Augmentation Of Stiffness Perception With a 1-Degree-of-Freedom Skin Stretch Device IEEE TRANSACTIONS ON HUMAN-MACHINE SYSTEMS Quek, Z. F., Schorr, S. B., Nisky, I., Okamura, A. M., Provancher, W. R. 2014; 44 (6): 731-742

  View details for DOI 10.1109/THMS.2014.2348865

  View details for Web of Science ID 000346225700004

• Testing models of cerebellar ataxia via dynamic simulation ROBOTICA Grow, D., Bastian, A. J., Okamura, A. M. 2014; 32 (8): 1383-1397

  View details for DOI 10.1017/S0263574714002306

  View details for Web of Science ID 000346921000013

• Torsional Dynamics of Steerable Needles: Modeling and Fluoroscopic Guidance IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Swensen, J. P., Lin, M., Okamura, A. M., Cowan, N. J. 2014; 61 (11): 2707-2717

  View details for DOI 10.1109/TBME.2014.2326161

  View details for Web of Science ID 000344082000006

• Torsional dynamics of steerable needles: modeling and fluoroscopic guidance. IEEE transactions on bio-medical engineering Swensen, J. P., Lin, M., Okamura, A. M., Cowan, N. J. 2014; 61 (11): 2707-2717

  Abstract

  Needle insertions underlie a diversity of medical interventions. Steerable needles provide a means by which to enhance existing needle-based interventions and facilitate new ones. Tip-steerable needles follow a curved path and can be steered by twisting the needle base during insertion, but this twisting excites torsional dynamics that introduce a discrepancy between the base and tip twist angles. Here, we model the torsional dynamics of a flexible rod-such as a tip-steerable needle-during subsurface insertion and develop a new controller based on the model. The torsional model incorporates time-varying mode shapes to capture the changing boundary conditions inherent during insertion. Numerical simulations and physical experiments using two distinct setups-stereo camera feedback in semitransparent artificial tissue and feedback control with real-time X-ray imaging in optically opaque artificial tissue-demonstrate the need to account for torsional dynamics in control of the needle tip.

  View details for DOI 10.1109/TBME.2014.2326161

  View details for PubMedID 24860026

• Neural coding of passive lump detection in compliant artificial tissue JOURNAL OF NEUROPHYSIOLOGY Gwilliam, J. C., Yoshioka, T., Okamura, A. M., Hsiao, S. S. 2014; 112 (5): 1131-1141

  Abstract

  Here, we investigate the neural mechanisms of detecting lumps embedded in artificial compliant tissues. We performed a combined psychophysical study of humans performing a passive lump detection task with a neurophysiological study in nonhuman primates (Macaca mulatta) where we recorded the responses of peripheral mechanoreceptive afferents to lumps embedded at various depths in intermediates (rubbers) of varying compliance. The psychophysical results reveal that human lump detection is greatly degraded by both lump depth and decreased compliance of the intermediate. The neurophysiology results reveal that only the slowly adapting type 1 (SA1) afferents provide a clear spatial representation of lumps at all depths and that the representation is affected by lump size, depth, and compliance of the intermediate. The rapidly adapting afferents are considerably less sensitive to the lump. We defined eight neural response measures that we hypothesized could explain the psychophysical behavior, including peak firing rate, spatial spread of neural activity, and additional parameters derived from these measures. We find that peak firing rate encodes the depth of the lump, and the neural spatial spread of the SA1 response encodes for lump size but not lump shape. We also find that the perception of lump size may be affected by the compliance of the intermediate. The results show that lump detection is based on a spatial population code of the SA1 afferents, which is distorted by the depth of the lump and compliance of the tissue.

  View details for DOI 10.1152/jn.00032.2013

  View details for Web of Science ID 000341687200011

  View details for PubMedID 24805077

• Effects of robotic manipulators on movements of novices and surgeons SURGICAL ENDOSCOPY AND OTHER INTERVENTIONAL TECHNIQUES Nisky, I., Okamura, A. M., Hsieh, M. H. 2014; 28 (7): 2145-2158

  Abstract

  Robot-assisted surgery is widely adopted for many procedures but has not realized its full potential to date. Based on human motor control theories, the authors hypothesized that the dynamics of the master manipulators impose challenges on the motor system of the user and may impair performance and slow down learning. Although studies have shown that robotic outcomes are correlated with the case experience of the surgeon, the relative contribution of cognitive versus motor skill is unknown. This study quantified the effects of da Vinci Si master manipulator dynamics on movements of novice users and experienced surgeons and suggests possible implications for training and robot design.In the reported study, six experienced robotic surgeons and ten novice nonmedical users performed movements under two conditions: teleoperation of a da Vinci Si Surgical system and freehand. A linear mixed model was applied to nine kinematic metrics (including endpoint error, movement time, peak speed, initial jerk, and deviation from a straight line) to assess the effects of teleoperation and expertise. To assess learning effects, t tests between the first and last movements of each type were used.All the users moved slower during teleoperation than during freehand movements (F 1,9343 = 345; p < 0.001). The experienced surgeons had smaller errors than the novices (F 1,14 = 36.8; p < 0.001). The straightness of movements depended on their direction (F 7,9343 = 117; p < 0.001). Learning effects were observed in all conditions. Novice users first learned the task and then the dynamics of the manipulator.The findings showed differences between the novices and the experienced surgeons for extremely simple point-to-point movements. The study demonstrated that manipulator dynamics affect user movements, suggesting that these dynamics could be improved in future robot designs. The authors showed the partial adaptation of novice users to the dynamics. Future studies are needed to evaluate whether it will be beneficial to include early training sessions dedicated to learning the dynamics of the manipulator.

  View details for DOI 10.1007/s00464-014-3446-5

  View details for Web of Science ID 000338278800017

  View details for PubMedID 24519031

• Predicting and correcting ataxia using a model of cerebellar function BRAIN Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2014; 137: 1931-1944

  View details for DOI 10.1093/brain/awu115

  View details for Web of Science ID 000338646800020

• Predicting and correcting ataxia using a model of cerebellar function. Brain Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2014; 137: 1931-1944

  Abstract

  Cerebellar damage results in uncoordinated, variable and dysmetric movements known as ataxia. Here we show that we can reliably model single-joint reaching trajectories of patients (n = 10), reproduce patient-like deficits in the behaviour of controls (n = 11), and apply patient-specific compensations that improve reaching accuracy (P < 0.02). Our approach was motivated by the theory that the cerebellum is essential for updating and/or storing an internal dynamic model that relates motor commands to changes in body state (e.g. arm position and velocity). We hypothesized that cerebellar damage causes a mismatch between the brain's modelled dynamics and the actual body dynamics, resulting in ataxia. We used both behavioural and computational approaches to demonstrate that specific cerebellar patient deficits result from biased internal models. Our results strongly support the idea that an intact cerebellum is critical for maintaining accurate internal models of dynamics. Importantly, we demonstrate how subject-specific compensation can improve movement in cerebellar patients, who are notoriously unresponsive to treatment.

  View details for DOI 10.1093/brain/awu115

  View details for PubMedID 24812203

• Task-dependent impedance and implications for upper-limb prosthesis control INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Blank, A. A., Okamura, A. M., Whitcomb, L. L. 2014; 33 (6): 827-846

  View details for DOI 10.1177/0278364913517728

  View details for Web of Science ID 000337560700001

• Haptic feedback enhances rhythmic motor control by reducing variability, not improving convergence rate JOURNAL OF NEUROPHYSIOLOGY Ankarali, M. M., Sen, H. T., De, A., Okamura, A. M., Cowan, N. J. 2014; 111 (6): 1286-1299

  Abstract

  Stability and performance during rhythmic motor behaviors such as locomotion are critical for survival across taxa: falling down would bode well for neither cheetah nor gazelle. Little is known about how haptic feedback, particularly during discrete events such as the heel-strike event during walking, enhances rhythmic behavior. To determine the effect of haptic cues on rhythmic motor performance, we investigated a virtual paddle juggling behavior, analogous to bouncing a table tennis ball on a paddle. Here, we show that a force impulse to the hand at the moment of ball-paddle collision categorically improves performance over visual feedback alone, not by regulating the rate of convergence to steady state (e.g., via higher gain feedback or modifying the steady-state hand motion), but rather by reducing cycle-to-cycle variability. This suggests that the timing and state cues afforded by haptic feedback decrease the nervous system's uncertainty of the state of the ball to enable more accurate control but that the feedback gain itself is unaltered. This decrease in variability leads to a substantial increase in the mean first passage time, a measure of the long-term metastability of a stochastic dynamical system. Rhythmic tasks such as locomotion and juggling involve intermittent contact with the environment (i.e., hybrid transitions), and the timing of such transitions is generally easy to sense via haptic feedback. This timing information may improve metastability, equating to less frequent falls or other failures depending on the task.

  View details for DOI 10.1152/jn.00140.2013

  View details for Web of Science ID 000335775500012

  View details for PubMedID 24371296

• Mapping stiffness perception in the brain with an fMRI-compatible particle-jamming haptic interface. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference Menon, S., Stanley, A. A., Zhu, J., Okamura, A. M., Khatib, O. 2014; 2014: 2051-2056

  Abstract

  We demonstrate reliable neural responses to changes in haptic stiffness perception using a functional magnetic resonance imaging (fMRI) compatible particle-jamming haptic interface. Our haptic interface consists of a silicone tactile surface whose stiffness we can control by modulating air-pressure in a sub-surface pouch of coarsely ground particles. The particles jam together as the pressure decreases, which stiffens the surface. During fMRI acquisition, subjects performed a constant probing task, which involved continuous contact between the index fingertip and the interface and rhythmic increases and decreases in fingertip force (1.6 Hz) to probe stiffness. Without notifying subjects, we randomly switched the interface's stiffness (switch time, 300-500 ms) from soft (200 N/m) to hard (1400 N/m). Our experiment design's constant motor activity and cutaneous tactile sensation helped disassociate neural activation for both from stiffness perception, which helped localized it to a narrow region in somatosensory cortex near the supra-marginal gyrus. Testing different models of neural activation, we found that assuming indepedent stiffness-change responses at both soft-hard and hard-soft transitions provides the best explanation for observed fMRI measurements (three subjects; nine four-minute scan runs each). Furthermore, we found that neural activation related to stiffness-change and absolute stiffness can be localized to adjacent but disparate anatomical locations. We also show that classical finger-tapping experiments activate a swath of cortex and are not suitable for localizing stiffness perception. Our results demonstrate that decorrelating motor and sensory neural activation is essential for characterizing somatosensory cortex, and establish particle-jamming haptics as an attractive low-cost method for fMRI experiments.

  View details for DOI 10.1109/EMBC.2014.6944019

  View details for PubMedID 25570387

• Real-time 3D curved needle segmentation using combined B-mode and power Doppler ultrasound. Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention Greer, J. D., Adebar, T. K., Hwang, G. L., Okamura, A. M. 2014; 17: 381-388

  Abstract

  This paper presents a real-time segmentation method for curved needles in biological tissue based on analysis of B-mode and power Doppler images from a tracked 2D ultrasound transducer. Mechanical vibration induced by an external voice coil results in a Doppler response along the needle shaft, which is centered around the needle section in the ultrasound image. First, B-mode image analysis is performed within regions of interest indicated by the Doppler response to create a segmentation of the needle section in the ultrasound image. Next, each needle section is decomposed into a sequence of points and transformed into a global coordinate system using the tracked transducer pose. Finally, the 3D shape is reconstructed from these points. The results of this method differ from manual segmentation by 0.71 ± 0.55 mm in needle tip location and 0.38 ± 0.27 mm along the needle shaft. This method is also fast, taking 5-10 ms to run on a standard PC, and is particularly advantageous in robotic needle steering, which involves thin, curved needles with poor echogenicity.

  View details for PubMedID 25485402

• Grip Force Control during Virtual Object Interaction: Effect of Force Feedback, Accuracy Demands, and Training IEEE TRANSACTIONS ON HAPTICS Gibo, T. L., Bastian, A. J., Okamura, A. M. 2014; 7 (1): 37-47

  Abstract

  When grasping and manipulating objects, people are able to efficiently modulate their grip force according to the experienced load force. Effective grip force control involves providing enough grip force to prevent the object from slipping, while avoiding excessive force to avoid damage and fatigue. During indirect object manipulation via teleoperation systems or in virtual environments, users often receive limited somatosensory feedback about objects with which they interact. This study examines the effects of force feedback, accuracy demands, and training on grip force control during object interaction in a virtual environment. The task required subjects to grasp and move a virtual object while tracking a target. When force feedback was not provided, subjects failed to couple grip and load force, a capability fundamental to direct object interaction. Subjects also exerted larger grip force without force feedback and when accuracy demands of the tracking task were high. In addition, the presence or absence of force feedback during training affected subsequent performance, even when the feedback condition was switched. Subjects' grip force control remained reminiscent of their employed grip during the initial training. These results motivate the use of force feedback during telemanipulation and highlight the effect of force feedback during training.

  View details for DOI 10.1109/TOH.2013.60

  View details for Web of Science ID 000336913100005

  View details for PubMedID 24845744

• Real-Time 3D Curved Needle Segmentation Using Combined B-Mode and Power Doppler Ultrasound MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2014, PT II Greer, J. D., Adebar, T. K., Hwang, G. L., Okamura, A. M. 2014; 8674: 381-388

  View details for Web of Science ID 000347686400048

• Integration of a Particle Jamming Tactile Display with a Cable-Driven Parallel Robot HAPTICS: NEUROSCIENCE, DEVICES, MODELING, AND APPLICATIONS, PT II Stanley, A. A., Mayhew, D., Irwin, R., Okamura, A. M. 2014; 8619: 258-265

  View details for DOI 10.1007/978-3-662-44196-1_32

  View details for Web of Science ID 000345644600032

• Recursive Estimation of Needle Pose for Control of 3D-Ultrasound-Guided Robotic Needle Steering 2014 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS 2014) Adebar, T. K., Okamura, A. M. 2014: 4303-4308

  View details for Web of Science ID 000349834604062

• The effect of a robot-assisted surgical system on the kinematics of user movements. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Nisky, I., Hsieh, M. H., Okamura, A. M. 2013; 2013: 6257-6260

  Abstract

  Teleoperated robot-assisted surgery (RAS) offers many advantages over traditional minimally invasive surgery. However, RAS has not yet realized its full potential, and it is not clear how to optimally train surgeons to use these systems. We hypothesize that the dynamics of the master manipulator impact the ability of users to make desired movements with the robot. We compared freehand and teleoperated movements of novices and experienced surgeons. To isolate the effects of dynamics from procedural knowledge, we chose simple movements rather than surgical tasks. We found statistically significant effects of teleoperation and user expertise in several aspects of motion, including target acquisition error, movement speed, and movement smoothness. Such quantitative assessment of human motor performance in RAS can impact the design of surgical robots, their control, and surgeon training methods, and eventually, improve patient outcomes.

  View details for DOI 10.1109/EMBC.2013.6610983

  View details for PubMedID 24111170

• Novel algorithm for real-time onset detection of surface electromyography in step-tracking wrist movements. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Kuroda, Y., Nisky, I., Uranishi, Y., Imura, M., Okamura, A. M., Oshiro, O. 2013; 2013: 2056-2059

  Abstract

  We present a novel algorithm for real-time detection of the onset of surface electromyography signal in step-tracking wrist movements. The method identifies abrupt increase of the quasi-tension signal calculated from sEMG resulting from the step-by-step recruitment of activated motor units. We assessed the performance of our proposed algorithm using both simulated and real sEMG signals, and compared with two existing detection methods. Evaluation with simulated sEMG showed that the detection accuracy of our method is robust to different signal-to-noise ratios, and that it outperforms the existing methods in terms of bias when the noise is large (low SNR). Evaluation with real sEMG analysis also indicated better detection performance compared to existing methods.

  View details for DOI 10.1109/EMBC.2013.6609936

  View details for PubMedID 24110123

• Cerebellar motor learning: are environment dynamics more important than error size? JOURNAL OF NEUROPHYSIOLOGY Gibo, T. L., Criscimagna-Hemminger, S. E., Okamura, A. M., Bastian, A. J. 2013; 110 (2): 322-333

  Abstract

  Cerebellar damage impairs the control of complex dynamics during reaching movements. It also impairs learning of predictable dynamic perturbations through an error-based process. Prior work suggests that there are distinct neural mechanisms involved in error-based learning that depend on the size of error experienced. This is based, in part, on the observation that people with cerebellar degeneration may have an intact ability to learn from small errors. Here we studied the relative effect of specific dynamic perturbations and error size on motor learning of a reaching movement in patients with cerebellar damage. We also studied generalization of learning within different coordinate systems (hand vs. joint space). Contrary to our expectation, we found that error size did not alter cerebellar patients' ability to learn the force field. Instead, the direction of the force field affected patients' ability to learn, regardless of whether the force perturbations were introduced gradually (small error) or abruptly (large error). Patients performed best in fields that helped them compensate for movement dynamics associated with reaching. However, they showed much more limited generalization patterns than control subjects, indicating that patients rely on a different learning mechanism. We suggest that patients typically use a compensatory strategy to counteract movement dynamics. They may learn to relax this compensatory strategy when the external perturbation is favorable to counteracting their movement dynamics, and improve reaching performance. Altogether, these findings show that dynamics affect learning in cerebellar patients more than error size.

  View details for DOI 10.1152/jn.00745.2012

  View details for Web of Science ID 000321843800005

  View details for PubMedID 23596337

• Adaptation to visuomotor rotation in isometric reaching is similar to movement adaptation. IEEE ... International Conference on Rehabilitation Robotics : [proceedings] Rotella, M. F., Koehler, M., Nisky, I., Bastian, A. J., Okamura, A. M. 2013; 2013: 1-6

  Abstract

  Isometric reaching, in which the arm remains stationary and the user controls a virtual cursor via force input, is a motor task that has not been thoroughly compared to real reaching. In this study, we ask if isometric adaptation to a kinematic perturbation is similar to adaptation in movement, and if the type of isometric mapping (position or velocity control) influences learning. Healthy subjects made real and virtual reaches with the arm in plane. In some trials, the cursor was rotated counter clockwise by 45° to perturb the kinematic mapping. To assess adaptation, the angular error of cursor movement at 150 ms from movement onset was measured for each reach; error was averaged across subjects and a two-state learning mode was fit to error data. For movement and isometric groups, average angular error peaked at perturbation onset, reduced over 200 reaches, and reversed direction when the perturbation was removed. We show that subjects are able to adapt to a visuomotor rotation in both position- and velocity-based cursor control, and that the time course of adaptation resembles that of movement adaptation. Training of virtual reaching using force/torque input could be particularly applicable for stroke patients with significant movement deficits, who could benefit from intensive treatments using simple, cost-effective devices.

  View details for DOI 10.1109/ICORR.2013.6650431

  View details for PubMedID 24187249

• Effect of age on stiffness modulation during postural maintenance of the arm. IEEE ... International Conference on Rehabilitation Robotics : [proceedings] Gibo, T. L., Bastian, A. J., Okamura, A. M. 2013; 2013: 1-6

  Abstract

  The ability to modify the mechanical impedance of our limbs allows us to perform a variety of motor control tasks while interacting with the environment in a stable manner. Prior work has shown that young, healthy people are capable of modulating arm stiffness via selective muscle co-contraction to account for external disturbances in various directions. Increased age detrimentally affects control of movement and stability, although the neural mechanisms underlying these deficits are not entirely understood. In this study, younger and older subjects performed a static postural maintenance task with two types of directional force perturbations. Older individuals showed significantly less stiffness modification between the two perturbation conditions compared to the younger individuals, indicating less optimal modulation of arm impedance. This impairment should be considered during motor control evaluation in older populations, whether it be activities of daily living or skill assessment.

  View details for DOI 10.1109/ICORR.2013.6650395

  View details for PubMedID 24187214

• Characterization and psychophysical studies of an air-jet lump display. IEEE transactions on haptics Gwilliam, J. C., Bianchi, M., Su, L. K., Okamura, A. M. 2013; 6 (2): 156-166

  Abstract

  Development of tactile displays to enhance palpation of lumps during robot-assisted minimally invasive surgery is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. This work describes the quantitative and psychophysical assessment of an air-jet tactile display that creates a lump percept by directing pressurized air through an aperture onto the finger. The air pressure and aperture size are meant to control the hardness and size, respectively, of the perceived lump. Jet impingement pressure and flow rate were measured by capacitive tactile sensors and mass flow meters at varying aperture sizes and pressures. The air-jet pressure profile width evolves as jet theory predicts and is largely independent of supply pressure (and therefore jet exit velocity). The method of constant stimuli was used to determine the just noticeable differences (JNDs) for the air pressure and aperture size. Qualitative results indicate that subjects perceive the stimulus as a "lump-like" shape. Pressure JNDs ranged from 19.6-24.4 kPag and aperture size JNDs ranged from 0.50-0.66 mm. No significant correlation exists between the supply pressure and changes in perceived lump size. However, pressure JNDs show significant (p < 0.001) inverse correlation with aperture size, with improved discrimination at larger apertures, where a greater finger pad area is stimulated.

  View details for DOI 10.1109/TOH.2012.71

  View details for PubMedID 24808300

• Does a basic deficit in force control underlie cerebellar ataxia? JOURNAL OF NEUROPHYSIOLOGY Charles, S. K., Okamura, A. M., Bastian, A. J. 2013; 109 (4): 1107-1116

  Abstract

  Because damage to the cerebellum results in characteristic movement incoordination known as "ataxia," it has been hypothesized that it is involved in estimation of limb dynamics that occur during movement. However, cerebellar function may extend beyond movement to force control in general, with or without movement. Here we tested whether the cerebellum is involved in controlling force separate from estimating limb dynamics and whether ataxia could result from a deficit in force control. We studied patients with cerebellar ataxia controlling their arm force isometrically; in this condition arm dynamics are absent and there is no need for (or effect from an impairment in) estimations of limb dynamics. Subjects were required to control their force magnitude, direction, or both. Cerebellar patients were able to match force magnitude or direction similarly to control subjects. Furthermore, when controlling force magnitude, they intuitively chose directions (not specified) that required minimal effort at the joint level--this ability was also similar to control subjects. In contrast, cerebellar patients performed significantly worse than control subjects when asked to match both force magnitude and direction. This was surprising, since they did not exhibit significant impairment in doing either in isolation. These results show that cerebellum-dependent computations are not limited to estimations of body dynamics needed for active movement. Deficits occur even in isometric conditions, but apparently only when multiple degrees of freedom must be controlled simultaneously. Thus a fundamental cerebellar operation may be combining/coordinating degrees of freedom across many kinds of movements and behaviors.

  View details for DOI 10.1152/jn.00152.2012

  View details for Web of Science ID 000315141100021

  View details for PubMedID 23175807

• Sensory Augmentation of Stiffness using Fingerpad Skin Stretch 2013 WORLD HAPTICS CONFERENCE (WHC) Quek, Z. F., Schorr, S. B., Nisky, I., Okamura, A. M., Provancher, W. R. 2013: 467-472

  View details for Web of Science ID 000325187400079

• A HAPTIC SYSTEM FOR EDUCATIONAL GAMES: DESIGN AND APPLICATION-SPECIFIC KINEMATIC OPTIMIZATION ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE, VOL 2 Kessler, J. A., Lovelace, R. C., Okamura, A. M. 2013

  View details for DOI 10.1115/DSCC2013-4077

  View details for Web of Science ID 000337043200054

• ROBOT-GUIDED SHEATHS (RoGS) FOR PERCUTANEOUS ACCESS TO THE PEDIATRIC KIDNEY: PATIENT-SPECIFIC DESIGN AND PRELIMINARY RESULTS PROCEEDINGS OF THE ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE (DSCC2013), VOL. 1 Morimoto, T. K., Hsieh, M. H., Okamura, A. M. 2013

  View details for DOI 10.1115/DSCC2013-3917

  View details for Web of Science ID 000335377800043

• A Framework for Analysis of Surgeon Arm Posture Variability in Robot-Assisted Surgery 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Nisky, I., Hsieh, M. H., Okamura, A. M. 2013: 245-251

  View details for Web of Science ID 000337617300036

• Arm Stiffness in Patients with Cerebellar Ataxia: Modulation during Postural Maintenance and its Subsequent Effects on Movement. Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013
• Sensory Substitution via Cutaneous Skin Stretch Feedback. Schorr, S., B., Quek, Z., F., Romano, R., Y., Nisky, I., Provancher, W., R., Okamura, A., M. 2013
• A Haptic System for Educational Games: Design and Application-Specific Kinematic Optimization. Kessler, J., A., Lovelace, R., C., Okamura, A., M. 2013
• A Framework for Analysis of Surgeon Arm Posture Variability in Robot-Assisted Surgery. Nisky, I., Hsieh, M., H., Okamura, A., M. 2013
• Autonomous Robotic Palpation: Machine Learning Techniques to Identify Hard Inclusions in Soft Tissues 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Nichols, K. A., Okamura, A. M. 2013: 4384-4389

  View details for Web of Science ID 000337617304060

• MODEL-MEDIATED TELEOPERATION WITH PREDICTIVE MODELS AND RELATIVE TRACKING ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE, VOL 2 Winck, R. C., Okamura, A. M. 2013

  View details for DOI 10.1115/DSCC2013-3842

  View details for Web of Science ID 000337043200051

• Tissue Fixation by Suction Increases the Accuracy of Robotic Needle Insertion 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Wedlick, T. R., Lin, D. J., Okamura, A. M. 2013: 1694-1699

  View details for Web of Science ID 000337617301104

• Sensory Substitution via Cutaneous Skin Stretch Feedback 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Schorr, S. B., Quek, Z. F., Romano, R. Y., Nisky, I., Provancher, W. R., Okamura, A. M. 2013: 2341-2346

  View details for Web of Science ID 000337617302052

• Sensorimotor Performance in Robot Assisted Surgery. Nisky, I., Hsieh, M., H., Okamura, A., M. 2013
• Cartesian and Joint Space Teleoperation for Nonholonomic Steerable Needles 2013 WORLD HAPTICS CONFERENCE (WHC) Majewicz, A., Okamura, A. M. 2013: 395-400

  View details for Web of Science ID 000325187400067

• Novel Algorithm for Real-Time Onset Detection of Surface Electromyography in Step-Tracking Wrist Movements. Kuroda, Y., Nisky, I., Uranishi, Y., Imura, M., Okamura, A., M., Oshiro, O. 2013
• Cerebellar Ataxia Impairs Modulation of Arm Stiffness during Postural Maintenance. Journal of Neurophysiology Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013; 7 (110): 1611-1620
• A Haptic Display for Medical Simulation Using Particle Jamming. Medicine Meets Virtual Reality (Studies in Health Technology and Information). Stanley, A., Gwilliam, J., C., Okamura, A., M. 2013
• 3D Segmentation of Curved Needles using Doppler Ultrasound and Vibration. Information Processing in Computer-Assisted Interventions Adebar, T., K., Okamura, A., M. 2013: 61-70
• Kinematic Analysis of Motor Performance in Robot-Assisted Surgery: Implications for Robot Design and Surgical Training. Nisky, I., Patil, S., Hsieh, M., H., Okamura, A., M. 2013
• Robot-Guided Sheaths (RoGS) for Percutaneous Access to the Pedatric Kidney: Patient-Specific Design and Preliminary Results. Morimoto, T., K., Hsieh, M., H., Okamura, A., M. 2013
• Effect of Age on Stiffness Modulation during Postural Maintenance of the Arm. Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013

  View details for DOI 10.1109/ICORR.2014.6650395

• Autonomous Robotic Palpation: Machine Learning Techniques to Identify Hard Inclusions in Soft Tissues. Nichols, K., A., Okamura, A., M. 2013
• Adaptation to Visuomotor Rotation in Isometric Virtual Reaching Parallels Learning in Movement. Rotella, M., F., Koehler, M., Nisky, I., Bastian, A., J., Okamura, A., M. 2013
• 3D Segmentation of Curved Needles using Doppler Ultrasound and Vibration. Information Processing in Computer-Assisted Interventions Adebar, T., K., Okamura, A., M. 2013: 61-70
• Transfer of isometric motor learning depends on the mapping of force input to cursor movement. Rotella, M., F., Koehler, M., Nisky, I., Bastian, A., J., Okamura, A., M. 2013
• Tissue Fixation by Suction Increases the Accuracy of Robotic Needle Insertion. Wedlick, T., R., Lin, D., J., Okamura, A., M. 2013
• Model-Mediated Teleoperation with Predictive Models and Relative Tracking. Wedlick, R., C., Okamura, A., M. 2013
• Grip Force Control During Virtual Object Interaction: Effect of Force Feedback, Accuracy Demands, and Training. IEEE Transactions on Haptics Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013

  View details for DOI 10.1109/TOH.2014.60

• Kinematic analysis of motor performance in robot-assisted surgery: a preliminary study. Studies in health technology and informatics Nisky, I., Patil, S., Hsieh, M. H., Okamura, A. M. 2013; 184: 302-308

  Abstract

  The inherent dynamics of the master manipulator of a teleoperated robot-assisted surgery (RAS) system can affect the movements of a human operator, in comparison with free-space movements. To measure the effects of these dynamics on operators with differing levels of surgical expertise, a da Vinci Si system was instrumented with a custom surgeon grip fixture and magnetic pose trackers. We compared users' performance of canonical motor control movements during teleoperation with the manipulator and freehand cursor control, and found significant differences in several aspects of motion, including target acquisition error, movement speed, and acceleration. In addition, there was preliminary evidence for differences between experts and novices. These findings could impact robot design, control, and training methods for RAS.

  View details for PubMedID 23400175

• Haptic Jamming: A Deformable Geometry, Variable Stiffness Tactile Display using Pneumatics and Particle Jamming 2013 WORLD HAPTICS CONFERENCE (WHC) Stanley, A. A., Gwilliam, J. C., Okamura, A. M. 2013: 25-30

  View details for Web of Science ID 000325187400005

• Active force perception depends on cerebellar function JOURNAL OF NEUROPHYSIOLOGY Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2012; 107 (6): 1612-1620

  Abstract

  Damage to the cerebellum causes characteristic movement abnormalities but is thought to have minimal impact on somatosensory perception. Traditional clinical assessments of patients with cerebellar lesions reveal no perceptual deficits despite the fact that the cerebellum receives substantial somatosensory information. Given that abnormalities have been reported in predicting the visual consequences of movement, we suspect that the cerebellum broadly participates in perception when motor output is required (i.e., active perception). Thus we hypothesize that cerebellar integrity is essential for somatosensory perception that requires motor activity, but not passive somatosensory perception. We compared the perceptual acuity of human cerebellar patients to that of healthy control subjects in several different somatosensory perception tasks with minimal visual information. We found that patients were worse at active force and stiffness discrimination but similar to control subjects with regard to passive cutaneous force detection, passive proprioceptive detection, and passive proprioceptive discrimination. Furthermore, the severity of movement symptoms as assessed by a clinical exam was positively correlated with impairment of active force perception. Notably, within the context of these perceptual tasks, control subjects and cerebellar patients displayed similar movement characteristics, and hence differing movement strategies are unlikely to underlie the differences in perception. Our results are consistent with the hypothesis that the cerebellum is vital to sensory prediction of self-generated movement and suggest a general role for the cerebellum in multiple forms of active perception.

  View details for DOI 10.1152/jn.00983.2011

  View details for Web of Science ID 000302140300008

  View details for PubMedID 22190620

• Augmented reality and haptic interfaces for robot-assisted surgery INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY Yamamoto, T., Abolhassani, N., Jung, S., Okamura, A. M., Judkins, T. N. 2012; 8 (1): 45-56

  Abstract

  Current teleoperated robot-assisted minimally invasive surgical systems do not take full advantage of the potential performance enhancements offered by various forms of haptic feedback to the surgeon. Direct and graphical haptic feedback systems can be integrated with vision and robot control systems in order to provide haptic feedback to improve safety and tissue mechanical property identification.An interoperable interface for teleoperated robot-assisted minimally invasive surgery was developed to provide haptic feedback and augmented visual feedback using three-dimensional (3D) graphical overlays. The software framework consists of control and command software, robot plug-ins, image processing plug-ins and 3D surface reconstructions.The feasibility of the interface was demonstrated in two tasks performed with artificial tissue: palpation to detect hard lumps and surface tracing, using vision-based forbidden-region virtual fixtures to prevent the patient-side manipulator from entering unwanted regions of the workspace.The interoperable interface enables fast development and successful implementation of effective haptic feedback methods in teleoperation.

  View details for DOI 10.1002/rcs.421

  View details for Web of Science ID 000301120100005

  View details for PubMedID 22069247

• M-Width: Stability and Accuracy of Haptic Rendering of Virtual Mass. In Robotics: Science and Systems. Colonnese, N., Okamura, A., M. 2012
• Haptic Footstep Display. Jayakumar, R., P., Mishra, S., K., Dannenhoffer, J., F., Okamura, A., M. 2012
• Development of the KineSys MedSim: A Novel Hands-Free Haptic Robot for Medical Simulation. Medicine Meets Virtual Reality (Studies in Health Technology and Information). Judkins, T., N., Stevenson, M., Mayhew, D., Okamura, A., M. 2012
• Haptic feedback enhances rhythmic motor control performance. Ankarali, M., Mert, Sen, H., Tutkun, Okamura, Allison, M., Cowan, Noah, J. 2012
• Predicting and correcting human ataxia using a model of cerebellar function. Bhanpuri, N., Okamura, A., M., Bastian, A., J. 2012
• HAPI Bands: A Haptic Augmented Posture Interface. Rotella, M., F., Guerin, K., He, X., Okamura, A., M. 2012
• Design and Control of an Air-Jet Lump Display. Gwilliam, J., C., Degirmenci, A., Bianchi, M., Okamura, A., M. 2012
• Conveying the Configuration of a Virtual Human Hand Using Vibrotactile Feedback. Cheng, A., Nichols, K., A., Weeks, H., M., Gurari, N., Okamura, A., M. 2012
• Discrimination of Springs with Vision, Proprioception, and Artificial Skin Stretch Cues. Gurari, N., Wheeler, J., Shelton, A., Okamura, A., M. 2012
• Augmented Reality and Haptic Interfaces for Robot-Assisted Surgery. International Journal of Medical Robotics and Computer Assisted Surgery Yamamoto, T., Abolhassani, N., Jung, S., Okamura, A., M., Judkins, T., N. 2012; 1 (8): 45-46
• Characterization of Robotic Needle Insertion and Rotation in Artificial and Ex Vivo Tissues 2012 4TH IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB) Wedlick, T. R., Okamura, A. M. 2012: 62-68

  View details for Web of Science ID 000313014600011

• Wearable Haptic Device for Cutaneous Force and Slip Speed Display 2012 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Damian, D. D., Ludersdorfer, M., Kim, Y., Arieta, A. H., Pfeifer, R., Okamura, A. M. 2012: 1038-1043

  View details for Web of Science ID 000309406701007

• User comprehension of task performance with varying impedance in a virtual prosthetic arm: A pilot study 2012 4TH IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB) Blank, A., Okamura, A. M., Whitcomb, L. L. 2012: 500-507

  View details for Web of Science ID 000313014600085

• Robot-Assisted Needle Steering IEEE ROBOTICS & AUTOMATION MAGAZINE Reed, K. B., Majewicz, A., Kallem, V., Alterovitz, R., Goldberg, K., Cowan, N. J., Okamura, A. M. 2011; 18 (4): 35-46

  View details for DOI 10.1109/MRA.2011.942997

  View details for Web of Science ID 000297994600010

• Haptics in Medicine and Clinical Skill Acquisition IEEE TRANSACTIONS ON HAPTICS Okamura, A. M., Basdogan, C., Baillie, S., Harwin, W. S. 2011; 4 (3): 153-154

  View details for Web of Science ID 000293455500001

• Experimental evaluation of a coaxial needle insertion assistant with enhanced force feedback 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) De Lorenzo, D., Koseki, Y., De Momi, E., Chinzei, K., Okamura, A. M. 2011: 3447-3450

  Abstract

  During needle insertion in soft tissue, detection of change in tissue properties is important both for diagnosis to detect pathological tissue and for prevention to avoid puncture of important structures. The presence of a membrane located deep inside the tissue results in a relatively small force variation at the needle tip that can be masked by relatively large friction force between the needle shaft and the surrounding tissue. Also, user perception of force can be limited due to the overall small force amplitude in some applications (e.g. brain surgery). A novel robotic coaxial needle insertion assistant was developed to enhance operator force perception. The coaxial needle separates the cutting force at the needle tip from shear friction on the needle shaft. The assistant is force controlled (admittance control), providing the operator with force feedback that is a scaled version of the force applied by the needle tip to the tissue. The effectiveness of the assistant in enhancing the detection of different tissue types was tested experimentally. Users were asked to blindly insert a needle into artificial tissues with membranes at various depths under two force feedback conditions: (1) shaft and tip force together, and (2) only tip force. The ratio of successful to unsuccessful membrane detection was significantly higher when only the needle tip force is displayed to the user. The system proved to be compliant with the clinical applications requirements.

  View details for Web of Science ID 000298810002292

  View details for PubMedID 22255081

• Robotic Needle Steering: Design, Modeling, Planning, and Image Guidance. In Surgical Robotics - Systems, Applications, and Visions. Cowan, N., J., Goldberg, K., Chirikjian, G., S., Fichtinger, G., Alterovitz, R., Reed, K., B., Okamura, A. M. edited by Rosen, J., Hannaford, B., Satava, R. Springer. 2011: 557-582
• Task-Dependent Impedance Improves User Performance with a Virtual Prosthetic Arm 2011 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Blank, A., Okamura, A. M., Whitcomb, L. L. 2011: 2235-2242

  View details for Web of Science ID 000324383401071

• Characterization of an Air Jet Haptic Lump Display 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Bianchi, M., Gwilliam, J. C., Degirmenci, A., Okamura, A. M. 2011: 3467-3470

  Abstract

  During manual palpation, clinicians rely on distributed tactile information to identify and localize hard lumps embedded in soft tissue. The development of tactile feedback systems to enhance palpation using robot-assisted minimally invasive surgery (RMIS) systems is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. Recently, an air jet approach has been proposed for generating a lump percept. We use this technique to direct a thin stream of air through an aperture directly on the finger pad, which indents the skin in a hemispherical manner, producing a compelling lump percept. We hypothesize that the perceived parameters of the lump (e.g. size and stiffness) can be controlled by jointly adjusting air pressure and the aperture size through which air escapes. In this work, we investigate how these control variables interact to affect perceived pressure on the finger pad. First, we used a capacitive tactile sensor array to measure the effect of aperture size on output pressure, and found that peak output pressure increases with aperture size. Second, we performed a psychophysical experiment for each aperture size to determine the just noticeable difference (JND) of air pressure on the finger pad. Subject-averaged pressure JND values ranged from 19.4-24.7 kPa, with no statistical differences observed between aperture sizes. The aperture-pressure relationship and the pressure JND values will be fundamental for future display control.

  View details for Web of Science ID 000298810002297

  View details for PubMedID 22255086

• Assessing the Quality of Force Feedback in Soft Tissue Simulation 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Basafa, E., Sefati, S., Okamura, A. M. 2011: 3451-3454

  Abstract

  Many types of deformable models have been proposed for simulation of soft tissue in surgical simulators, but their realism in comparison to actual tissue is rarely assessed. In this paper, a nonlinear mass-spring model is used for realtime simulation of deformable soft tissues and providing force feedback to a human operator. Force-deformation curves of real soft tissue samples were obtained experimentally, and the model was tuned accordingly. To test the realism of the model, we conducted two human-user experiments involving palpation with a rigid probe. First, in a discrimination test, users identified the correct category of real and virtual tissue better than chance, and tended to identify the tissues as real more often than virtual. Second, users identified real and virtual tissues by name, after training on only real tissues. The sorting accuracy was the same for both real and virtual tissues. These results indicate that, despite model limitations, the simulation could convey the feel of touching real tissues. This evaluation approach could be used to compare and validate various soft-tissue simulators.

  View details for Web of Science ID 000298810002293

  View details for PubMedID 22255082

• Gradual anisometric-isometric transition for human-machine interfaces 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Gibo, T. L., Rotella, M. F., Bastian, A. J., Okamura, A. M. 2011: 4507-4510

  Abstract

  Human-machine interfaces (HMIs) are widely used in biomedical applications, from teleoperated surgical systems to rehabilitation devices. This paper investigates a method of control that allows an HMI to transition from anisometric to isometric mode, shifting the control input from position to force as the user's movement is gradually reduced. Two different approaches for achieving this transition are discussed: one is based on the natural system dynamics, whereas the other involves selecting and controlling dynamics. The two approaches were implemented on a custom haptic device in a targeting task. Anisometric to isometric transitioning can potentially be used for training purposes, enabling transfer of what was learned in one mode to the other, as well as novel studies of the human sensorimotor system.

  View details for Web of Science ID 000298810003208

  View details for PubMedID 22255340

• Robot-Assisted Steerable Needles: Prototype Development and Feasibility Studies in an Animal Model. Vledder, Mark, G. Van, Majewicz, A., Marra, Steven, P., Song, Danny, Y., Okamura, Allison, M., Choti, M. A. 2011
• Do Cerebellar Patients Generalize after Abrupt or Gradual Motor Learning? Gibo, T., L., Okamura, A., M., Bastian, A., J. 2011
• Cerebellar predictions underlie the improvement of proprioceptive precision in active versus passive movements. Bhanpuri, N., Okamura, A., M., Bastian, A., J. 2011
• Task-Dependent Impedance Improves User Performance with a Virtual Prosthetic Arm. Blank, A., Okamura, A., M., Whitcomb, L., L. 2011
• Characterization of an Air Jet Haptic Lump Display. Bianchi, M., Gwilliam, J., C., Degirmenci, A., Okamura, A., M. 2011
• Cutaneous Force Display via Shaped Contacts. Ludersdorfer, M., Damian, D., D., Arieta, A., Hernandez, Pfeifer, R., Okamura, A., M. 2011
• Force Feedback and Sensory Substitution for Robot-Assisted Surgery. Surgical Robotics - Systems, Applications, and Visions Okamura, A., M., Verner, L., N., Yamamoto, T., Gwilliam, J., C., Griffiths, P., G. 2011: 419-448
• Coaxial Needle Insertion Assistant for Epidural Puncture 2011 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS Koseki, Y., De Lorenzo, D., Chinzei, K., Okamura, A. M. 2011

  View details for Web of Science ID 000297477502141

• Design and Evaluation of a Multi-Modal Haptic Skin Stimulation Apparatus 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Damian, D. D., Arieta, A. H., Okamura, A. M. 2011: 3455-3458

  Abstract

  Human grasping and manipulation are facilitated by cutaneous mechanoreceptors that provide information about contact location, pressure, and events such as making and breaking contact. A challenge in designing haptic feedback devices for the wearer of a prosthetic hand is simultaneous display of multiple types of haptic information. We present the preliminary design and evaluation of an apparatus for relaying multi-modal haptic information. The apparatus moves a set of contact points tangentially over the skin at a controlled speed, with controlled normal force. We apply this stimulus to an artificial skin instrumented with an embedded accelerometer, and characterize the resulting signals. Vibration frequency increases with applied normal force and tangential speed, whereas vibration amplitude increases with normal force and depends on skin properties. The results indicate that different forces and speeds can, under some conditions, be discriminated using vibration signals alone. Accurate identification of speeds is provided by series of vibration events that depend on the spatial distribution of contact points. This study motivates future work to perform human perception studies and create a wearable haptic display for prosthetics based on this concept.

  View details for Web of Science ID 000298810002294

  View details for PubMedID 22255083

• Mechanics of Flexible Needles Robotically Steered through Soft Tissue INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Misra, S., REED, K. B., Schafer, B. W., Ramesh, K. T., Okamura, A. M. 2010; 29 (13): 1640-1660

  View details for DOI 10.1177/0278364910369714

  View details for Web of Science ID 000283847100004

• Identifying the Role of Proprioception in Upper-Limb Prosthesis Control: Studies on Targeted Motion ACM TRANSACTIONS ON APPLIED PERCEPTION Blank, A., Okamura, A. M., Kuchenbecker, K. J. 2010; 7 (3)

  View details for DOI 10.1145/1773965.1773966

  View details for Web of Science ID 000279361800001

• Haptics for Robot-Assisted Minimally Invasive Surgery ROBOTICS RESEARCH Okamura, A. M., Verner, L. N., Reiley, C. E., Mahvash, M. 2010; 66: 361-372

  View details for Web of Science ID 000289498800030

• Plugfest 2009: Global Interoperability in Telerobotics and Telemedicine 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) King, H. H., Hannaford, B., Kwok, K., Yang, G., Griffiths, P., Okamura, A., Farkhatdinov, I., Ryu, J., Sankaranarayanan, G., Arikatla, V., Tadano, K., Kawashima, K., Peer, A., Schauss, T., Buss, M., Miller, L., Glozman, D., Rosen, J., Low, T. 2010: 1733-1738

  View details for Web of Science ID 000284150002005

• Estimation of Model Parameters for Steerable Needles 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Park, W., Reed, K. B., Okamura, A. M., Chirikjian, G. S. 2010: 3703-3708

  View details for Web of Science ID 000284150001111

• Human vs. Robotic Tactile Sensing: Detecting Lumps in Soft Tissue. Gwilliam, J., Pezzementi, Z., Jantho, E., Okamura, A., M., Hsiao, S., S. 2010
• Design of a Haptic Simulator for Osteosynthesis Screw Insertion. Majewicz, A., Glasser, J., Bauer, R., Belkoff, S., Mears, S., Okamura, A., M. 2010
• A Proposed Method for Correcting Coordination Deficits: Models and Simulation. Grow, D., I., Bhanpuri, N., H., Charles, S., K., Bastian, A., J., Okamura, A., M. 2010
• Does a Basic Deficit in Force Control Underlie Cerebellar Ataxia? Charles, S., K., Okamura, A., M., Bastian, A., J. 2010
• Modelling of non-linear elastic tissues for surgical simulation COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING Misra, S., Ramesh, K. T., Okamura, A. M. 2010; 13 (6): 811-818

  Abstract

  Realistic modelling of the interaction between surgical instruments and human organs has been recognised as a key requirement in the development of high-fidelity surgical simulators. Primarily due to computational considerations, most of the past real-time surgical simulation research has assumed linear elastic behaviour for modelling tissues, even though human soft tissues generally possess non-linear properties. For a non-linear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. Using constitutive equations of non-linear tissue models together with experiments, we show that the Poynting effect results in differences in force magnitude larger than the absolute human perception threshold for force discrimination in some tissues (e.g. myocardial tissues) but not in others (e.g. brain tissue simulants).

  View details for DOI 10.1080/10255840903505121

  View details for Web of Science ID 000285145800019

  View details for PubMedID 20503126

• The Cerebellum Contributes to Constant and Dynamic Load Perception but not Position Perception. Bhanpuri, N., H., Okamura, A., M., Bastian, A., J. 2010
• Defining Performance Tradeoffs for Multi-Degree-of-Freedom Bilateral Teleoperators with LQG Control. Griffiths, P., G., Okamura, A., M. 2010
• Medical and Healthcare Robotics: Achievements and Opportunities IEEE Robotics and Automation Magazine Okamura, A., M., Mataric, M., J., Christensen, H., I. 2010; 3 (17): 26-37
• Neural coding of lump detection in soft tissue. Gwilliam, J., C., Yoshioka, T., Okamura, A., M., Hsiao, S., S. 2010
• Plugfest 2009: Global Interoperability in Telerobotics and Telemedicine. King, H., H., Hannaford, B., Kwok, K., W., Yang, G., Z., Griffiths, P., G., Okamura, A., M. 2010
• Modeling of Nonlinear Elastic Tissues for Surgical Simulation. Computer Methods in Biomechanics and Biomedical Engineering Misra, S., Ramesh, K., T., Okamura, A., M. 2010; 6 (13): 811-818
• Haptic Feedback: Technology and Medical Applications. Handbook of Touch. Okamura, A., M. 2010
• Evaluation of Robotic Needle Steering in ex vivo Tissue 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Majewicz, A., Wedlick, T. R., Reed, K. B., Okamura, A. M. 2010: 2068-2073

  View details for Web of Science ID 000284150004147

• Defining Performance Tradeoffs for Multi-Degree-of-Freedom Bilateral Teleoperators with LQG Control 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC) Griffiths, P. G., Okamura, A. M. 2010: 3542-3547

  View details for Web of Science ID 000295049104016

• Modeling and Control of Needles With Torsional Friction IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Reed, K. B., Okamura, A. M., Cowan, N. J. 2009; 56 (12): 2905-2916

  Abstract

  A flexible needle can be accurately steered by robotically controlling the bevel tip orientation as the needle is inserted into tissue. Friction between the long, flexible needle shaft and the tissue can cause a significant discrepancy between the orientation of the needle tip and the orientation of the base where the needle angle is controlled. Our experiments show that several common phantom tissues used in needle steering experiments impart substantial friction forces to the needle shaft, resulting in a lag of more than 45 ( degrees ) for a 10 cm insertion depth in some phantoms; clinical studies report torques large enough to cause similar errors during needle insertions. Such angle discrepancies will result in poor performance or failure of path planners and image-guided controllers, since the needles used in percutaneous procedures are too small for state-of-the-art imaging to accurately measure the tip angle. To compensate for the angle discrepancy, we develop an estimator using a mechanics-based model of the rotational dynamics of a needle being inserted into tissue. Compared to controllers that assume a rigid needle in a frictionless environment, our estimator-based controller improves the tip angle convergence time by nearly 50% and reduces the path deviation of the needle by 70%.

  View details for DOI 10.1109/TBME.2009.2029240

  View details for Web of Science ID 000272042400016

  View details for PubMedID 19695979

• The importance of organ geometry and boundary constraints for planning of medical interventions MEDICAL ENGINEERING & PHYSICS Misra, S., Macura, K. J., Ramesh, K. T., Okamura, A. M. 2009; 31 (2): 195-206

  Abstract

  Realistic modeling of medical interventions involving tool-tissue interactions has been considered to be a key requirement in the development of high-fidelity simulators and planners. Organ geometry, soft-tissue constitutive laws, and boundary conditions imposed by the connective tissues surrounding the organ are some of the factors that govern the accuracy of medical intervention planning. In this study it is demonstrated that, for needle path planning, the organ geometry and boundary constraints surrounding the organ are the most important factors influencing the deformation. As an example, the procedure of needle insertion into the prostate (e.g. for biopsy or brachytherapy) is considered. Image segmentation is used to extract the anatomical details from magnetic resonance images, while object-oriented finite element analysis (OOF) software is used to generate finite element (FE) meshes from the segmented images. Two-dimensional FE simulations that account for complex anatomical details along with relative motion between the prostate and its surrounding structure using cohesive zone models are compared with traditional simulation models having simple organ geometry and boundary constraints. Nodal displacements for these simpler models were observed to be up to 14 times larger than those obtained from the anatomically accurate models.

  View details for DOI 10.1016/j.medengphy.2008.08.002

  View details for Web of Science ID 000263872200005

  View details for PubMedID 18815068

• Controlling a Robotically Steered Needle in the Presence of Torsional Friction ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Reed, K. B., Okamura, A. M., Cowan, N. J. 2009: 3598-3603

  View details for Web of Science ID 000276080401265

• Quantifying Perception of Nonlinear Elastic Tissue Models using Multidimensional Scaling WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Misra, S., Fuernstahl, P., Ramesh, K. T., Okamura, A. M., Harders, M. 2009: 570-575

  View details for Web of Science ID 000266714300093

• Force & Torque Feedback vs Force Only Feedback WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Verner, L. N., Okamura, A. M. 2009: 406-410

  View details for Web of Science ID 000266714300066

• Haptic feedback in robot-assisted minimally invasive surgery CURRENT OPINION IN UROLOGY Okamura, A. M. 2009; 19 (1): 102-107

  Abstract

  Robot-assisted minimally invasive surgery (RMIS) holds great promise for improving the accuracy and dexterity of a surgeon and minimizing trauma to the patient. However, widespread clinical success with RMIS has been marginal. It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting factor. This review explains the technical challenges of creating haptic feedback for robot-assisted surgery and provides recent results that evaluate the effectiveness of haptic feedback in mock surgical tasks.Haptic feedback systems for RMIS are still under development and evaluation. Most provide only force feedback, with limited fidelity. The major challenge at this time is sensing forces applied to the patient. A few tactile feedback systems for RMIS have been created, but their practicality for clinical implementation needs to be shown. It is particularly difficult to sense and display spatially distributed tactile information. The cost-benefit ratio for haptic feedback in RMIS has not been established.The designs of existing commercial RMIS systems are not conducive for force feedback, and creative solutions are needed to create compelling tactile feedback systems. Surgeons, engineers, and neuroscientists should work together to develop effective solutions for haptic feedback in RMIS.

  View details for DOI 10.1097/MOU.0b013e32831a478c

  View details for Web of Science ID 000262215600020

  View details for PubMedID 19057225

• Feedback Control for Steering Needles through 3D Deformable Tissue using Helical Paths. Robotics: Science and Systems. Hauser, K., Alterovitz, R., Chentanez, N., Okamura, A., Goldberg, K. 2009
• Observations and Models for Needle-Tissue Interactions ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Misra, S., Reed, K. B., Schafer, B. W., Ramesh, K. T., Okamura, A. M. 2009: 3423-3428

  View details for Web of Science ID 000276080401237

• Observations of Needle-Tissue Interactions 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20 Misra, S., Reed, K. B., Ramesh, K. T., Okamura, A. M. 2009: 262-265

  Abstract

  Needles with asymmetric bevel tips naturally bend when they are inserted into soft tissue. In this study, we present an analytical model for the loads developed at the bevel tip during needle-tissue interaction. The model calculates the loads based on the geometry of the bevel edge and gel material properties. The modeled transverse force developed at the tip is compared to forces measured experimentally. The analytical model explains the trends observed in the experiments. In addition to macroscopic studies, we also present microscopic observations of needle-tissue interactions. These results contribute to a mechanics-based model of robotic needle steering, extending previous work on kinematic models.

  View details for Web of Science ID 000280543600070

  View details for PubMedID 19963709

• Design Considerations and Human-Machine Performance of Moving Virtual Fixtures ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Gibo, T. L., Verner, L. N., Yuh, D. D., Okamura, A. M. 2009: 2958-2963

  View details for Web of Science ID 000276080401164

• Haptics as an Aid to Copying for People with Williams Syndrome WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Lee, J., Okamura, A. M., Landau, B. 2009: 356-361

  View details for Web of Science ID 000266714300061

• Stiffness Discrimination with Visual and Proprioceptive Cues. Gurari, N., Kuchenbecker, K., J., Okamura, A., M. 2009
• Can Cerebellar Dysmetria be Explained by an Incorrect Internal Model of Limb Dynamics? Bhanpuri, N., H., Grow, D., I., Okamura, A., M., Bastian, A., J. 2009
• Modeling and Control of Needles with Torsional Friction. IEEE Transactions on Biomedical Engineering Reed, K., B., Okamura, A., M., Cowan, N., J. 2009; 12 (56): 2905-2916
• Environment Discrimination with Vibration Feedback to the Foot, Arm, and Fingertip 2009 IEEE 11TH INTERNATIONAL CONFERENCE ON REHABILITATION ROBOTICS, VOLS 1 AND 2 Gurari, N., Smith, K., Madhav, M., Okamura, A. M. 2009: 398-403

  View details for Web of Science ID 000277086500056

• Tissue Property Estimation and Graphical Display for Teleoperated Robot-Assisted Surgery ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Yamamoto, T., Vagvolgyi, B., Balaji, K., Whitcomb, L. L., Okamura, A. M. 2009: 3117-3123

  View details for Web of Science ID 000276080401190

• Effects of Haptic and Graphical Force Feedback on Teleoperated Palpation ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Gwilliam, J. C., Mahvash, M., Vagvolgyi, B., Vacharat, A., Yuh, D. D., Okamura, A. M. 2009: 3315-3320

  View details for Web of Science ID 000276080401221

• Quantification and Reproduction of Human Hand Skin Stretch and its Effects on Proprioception. Greenwald, E., Pompe, J., Hsiao, S., Okamura, A. 2009
• Characterization of Pre-Curved Needles for Steering in Tissue 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20 Wedlick, T. R., Okamura, A. M. 2009: 1200-1203

  Abstract

  Needles with tip asymmetry deflect upon insertion into soft tissue, an effect that can be used to steer needles within the body. This paper presents a phenomenological characterization of the steering behavior of pre-curved needles, which have tip asymmetry due to curvature of the needle near the tip. We describe needle construction methods and a needle shaft triangulation algorithm to compute the shape of the needle based on images. Experimental results show that pre-curved needles possess greater dexterity than bevel-tipped needles and achieve radii of curvature similar to pre-bent needles. For long pre-curve arc lengths, the radius of curvature of the needle was found to approach the radius of curvature of the pre-curve. Pre-curved needles were found to display behaviors not seen with bevel-tipped needles, such as the insertion velocity influencing the path of the tip within the tissue and the ability to plastically deform the needle during steering.

  View details for Web of Science ID 000280543601032

  View details for PubMedID 19963994

• Stiffness Discrimination with Visual and Proprioceptive Cues WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Gurari, N., Kuchenbecker, K. J., Okamura, A. M. 2009: 121-126

  View details for Web of Science ID 000266714300022

• Surgical and Interventional Robotics: Part III Surgical Assistance Systems IEEE ROBOTICS & AUTOMATION MAGAZINE Hager, G. D., Okamura, A. M., Kazanzides, P., Whitcomb, L. L., Fichtinger, G., Taylor, R. H. 2008; 15 (4): 84-93

  View details for DOI 10.1109/MRA.2008.930401

  View details for Web of Science ID 000261616400012

• Modeling of tool-tissue interactions for computer-based surgical simulation: A literature review PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS Misra, S., Ramesh, K. T., Okamura, A. M. 2008; 17 (5): 463-491

  View details for Web of Science ID 000259865300003

• Surgical and interventional robotics: Part II - Surgical CAD-CAM systems IEEE ROBOTICS & AUTOMATION MAGAZINE Fichtinger, G., Kazanzides, P., Okamura, A. M., Hager, G. D., Whitcomb, L. L., Taylor, R. H. 2008; 15 (3): 94-102

  View details for DOI 10.1109/MRA.2008.927971

  View details for Web of Science ID 000259300600014

• Surgical and interventional robotics - Core concepts, technology, and design IEEE ROBOTICS & AUTOMATION MAGAZINE Kazanzides, P., Fichtinger, G., Hager, G. D., Okamura, A. M., Whitcomb, L. L., Taylor, R. H. 2008; 15 (2): 122-130

  View details for DOI 10.1109/MRA.2008.926390

  View details for Web of Science ID 000256801100017

• Modeling the forces of cutting with scissors IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Mahvash, M., Voo, L. M., Kim, D., Jeung, K., Wainer, J., Okamura, A. M. 2008; 55 (3): 848-856

  Abstract

  Modeling forces applied to scissors during cutting of biological materials is useful for surgical simulation. Previous approaches to haptic display of scissor cutting are based on recording and replaying measured data. This paper presents an analytical model based on the concepts of contact mechanics and fracture mechanics to calculate forces applied to scissors during cutting of a slab of material. The model considers the process of cutting as a sequence of deformation and fracture phases. During deformation phases, forces applied to the scissors are calculated from a torque-angle response model synthesized from measurement data multiplied by a ratio that depends on the position of the cutting crack edge and the curve of the blades. Using the principle of conservation of energy, the forces of fracture are related to the fracture toughness of the material and the geometry of the blades of the scissors. The forces applied to scissors generally include high-frequency fluctuations. We show that the analytical model accurately predicts the average applied force. The cutting model is computationally efficient, so it can be used for real-time computations such as haptic rendering. Experimental results from cutting samples of paper, plastic, cloth, and chicken skin confirm the model, and the model is rendered in a haptic virtual environment.

  View details for DOI 10.1109/TBME.2007.908069

  View details for Web of Science ID 000253733800001

  View details for PubMedID 18334376

• Needle-Tissue Interaction Forces for Bevel-Tip Steerable Needles 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Misra, S., Reed, K. B., Douglas, A. S., Ramesh, K. T., Okamura, A. M. 2008: 224-231

  View details for Web of Science ID 000270540400038

• The touch thimble: Providing fingertip contact feedback during point-force haptic interaction SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Kuchenbecker, K. J., Ferguson, D., Kutzer, M., Moses, M., Okamura, A. M. 2008: 239-246

  View details for Web of Science ID 000254949300034

• A Simulator to Explore the Role of Haptic Feedback in Cataract Surgery Training MEDICINE MEETS VIRTUAL REALITY 16 Doyle, L., Gauthier, N., Ramanathan, S., Okamura, A. 2008; 132: 106-111

  Abstract

  Phacoemulsification cataract surgery, a minimally invasive technique to remove a cloudy lens from the eye, is one of the most commonly performed surgical procedures in the western world. Conventional training for this procedure involves didactic lectures and practice on pig and human cadaver eyes, none of which allow trainees to form an accurate predictive model of human tissue behavior during surgery. A virtual environment simulator for capsulorrhexis, one of the first steps in cataract surgery, has been developed that allows a trainee to use surgical instruments to excise a circle of tissue on the anterior side of the lens capsule through tearing. The simulator invokes a deformable mass-spring-damper mesh model of the tissue that can be grasped and torn via shearing. A novel algorithm for mesh division and maintenance enables realistic tearing behavior. The trainee controls tool motion using a 3-degree-of-freedom haptic device, and haptic feedback is provided from the virtual tissue. Although the haptic feedback in a real capsulorrhexis procedure is below the human threshold of haptic sensing, this simulator enables an experiment to determine the effectiveness of "haptic training wheels" -- the idea of haptic training for a task without haptic feedback.

  View details for Web of Science ID 000272668400023

  View details for PubMedID 18391267

• Control Methods for Guidance Virtual Fixtures in Compliant Human-Machine Interfaces 2008 IEEE/RSJ INTERNATIONAL CONFERENCE ON ROBOTS AND INTELLIGENT SYSTEMS, VOLS 1-3, CONFERENCE PROCEEDINGS Marayong, P., Hager, G. D., Okamura, A. M. 2008: 1166-1172

  View details for Web of Science ID 000259998200183

• Chapter 30: Haptics. In Springer Handbook of Robotics Hannaford, B., Okamura, A., M. Springer. 2008: 719-739
• Force-feedback surgical teleoperator: Controller design and palpation experiments SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Mahvash, M., Gwilliam, J., Agarwal, R., Vagvolgyi, B., Su, L., Yuh, D. D., Okamura, A. M. 2008: 465-471

  View details for Web of Science ID 000254949300070

• A Simulator to Explore the Role of Haptic Feedback in Cataract Surgery Training. Medicine Meets Virtual Reality. Doyle, L., Gauthier, N., Ramanathan, S., Okamura, A., M. 2008
• Measurement-Based Modeling for Haptic Display. In Haptic Rendering: Foundations, Algorithms, and Applications. Okamura, A., M., Kuchenbecker, K., J., Mahvash, M. edited by Lin, M., C., Otaduy, M. AK Peters.. 2008: 1
• Effects of visual force feedback on robot-assisted surgical task performance JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY Reiley, C. E., Akinbiyi, T., Burschka, D., Chang, D. C., Okamura, A. M., Yuh, D. D. 2008; 135 (1): 196-202

  Abstract

  Direct haptic (force or tactile) feedback is negligible in current surgical robotic systems. The relevance of haptic feedback in robot-assisted performances of surgical tasks is controversial. We studied the effects of visual force feedback, a haptic feedback surrogate, on tying surgical knots with fine sutures similar to those used in cardiovascular surgery.By using a modified da Vinci robotic system (Intuitive Surgical, Inc, Sunnyvale, Calif) equipped with force-sensing instrument tips and real-time visual force feedback overlays in the console image, 10 surgeons each tied 10 knots with and 10 knots without visual force feedback. Four surgeons had significant prior da Vinci experience, and the remaining 6 surgeons did not. Performance parameters, including suture breakage and secure knots, peak and standard deviation of applied forces, and completion times using 5-0 silk sutures, were recorded. Chi-square and Student t test analyses determined the differences between groups.Among surgeon subjects with robotic experience, no differences in measured performance parameters were found between robot-assisted knot ties executed with and without visual force feedback. Among surgeons without robotic experience, however, visual force feedback was associated with lower suture breakage rates, peak applied forces, and standard deviations of applied forces. Visual force feedback did not impart differences in knot completion times or loose knots for either surgeon group.Visual force feedback resulted in reduced suture breakage, lower forces, and decreased force inconsistencies among novice robotic surgeons, although elapsed time and knot quality were unaffected. In contrast, visual force feedback did not affect these metrics among surgeons experienced with the da Vinci system. These results suggest that visual force feedback primarily benefits novice robot-assisted surgeons, with diminishing benefits among experienced surgeons.

  View details for DOI 10.1016/j.jtcvs.2007.08.043

  View details for Web of Science ID 000252139600029

  View details for PubMedID 18179942

• Techniques for Environment Parameter Estimation During Telemanipulation 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Yamamoto, T., Bernhardt, M., Peer, A., Buss, M., Okamura, A. M. 2008: 217-223

  View details for Web of Science ID 000270540400037

• Haptic simulation of elbow joint spasticity SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Grow, D. I., Wu, M. (., Locastro, M. J., Arora, S. K., Bastian, A. J., Okamura, A. M. 2008: 475-476

  View details for Web of Science ID 000254949300072

• Effects of proprioceptive motion feedback on sighted and non-sighted control of a virtual hand prosthesis SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Blank, A., Okamura, A. M., Kuchenbecker, K. J. 2008: 141-142

  View details for Web of Science ID 000254949300021

• Modeling realistic tool-tissue interactions with haptic feedback: A learning-based method SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Pezzernenti, Z., Ursu, D., Misra, S., Okamura, A. M. 2008: 209-215

  View details for Web of Science ID 000254949300030

• Compensating for Torsion Windup in Steerable Needles. Okamura, A., M., Reed, K., B. 2008
• The Touch Thimble: Providing Fingertip Contact Feedback During Point-Force Haptic Interaction. Kuchenbecker, K., J., Ferguson, D., Kutzer, M., Moses, M., Okamura, A., M. 2008
• Telemanipulators with Sensor/Actuator Asymmetries Fail the Robustness Criterion. Verner, L., N., Okamura, A., M. 2008
• Multi-Estimator Technique for Environment Parameter Estimation During Telemanipulation. Yamamoto, T., Bernhardt, M., Peer, A., Buss, M., Okamura, A., M. 2008
• Physically Valid Surgical Simulators: Linear Versus Nonlinear Tissue Models MEDICINE MEETS VIRTUAL REALITY 16 Misra, S., Ramesh, K. T., Okamura, A. M. 2008; 132: 293-295

  Abstract

  Realistic modeling of the interaction between surgical instruments and organs has been recognized as a key requirement in the development of high-fidelity surgical simulators. For a nonlinear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. It is demonstrated that the difference in force magnitude for myocardial tissue is larger than the just noticeable difference for contact force discrimination thresholds published in the psychophysics literature. This work also proposes the validation of simulators by careful examination of relevant simulator design parameters that relate to final simulator behaviors affecting clinical outcomes.

  View details for Web of Science ID 000272668400063

  View details for PubMedID 18391307

• Control Methods for Guidance Virtual Fixtures in Compliant Human-Machine Interfaces. Marayong, P., Hager, G., D., Okamura, A., M. 2008
• Integrated Planning and Image-Guided Control for Planar Needle Steering 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Reed, K. B., Kallem, V., Alterovitz, R., Goldberg, K., Okamura, A. M., Cowan, N. J. 2008: 907-912

  View details for Web of Science ID 000270540400151

• Friction compensation for enhancing transparency of a teleoperator with compliant transmission IEEE TRANSACTIONS ON ROBOTICS Mahvash, M., Okamura, A. 2007; 23 (6): 1240-1246

  View details for DOI 10.1109/TRO.2007.909825

  View details for Web of Science ID 000251944100013

• Pseudo-admittance bilateral telemanipulation with guidance virtual fixtures INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Abbott, J. J., Okamura, A. M. 2007; 26 (8): 865-884

  View details for DOI 10.1177/0278364907080425

  View details for Web of Science ID 000248543500006

• Human performance in a knob-turning task WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Gurari, N., Okamura, A. M. 2007: 96-101

  View details for Web of Science ID 000246105200017

• Teleoperation of steerable needles PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Romano, J. M., Webster, R. J., Okamura, A. M. 2007: 934-939

  View details for Web of Science ID 000250915300149

• Force feedback is noticeably different for linear versus nonlinear elastic tissue models WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Misra, S., Okamura, A. M., Ramesh, K. T. 2007: 519-524

  View details for Web of Science ID 000246105200086

• Virtual fixture control for compliant human-machine interfaces PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Marayong, P., Na, H. S., Okamura, A. M. 2007: 4018-4024

  View details for Web of Science ID 000250915304004

• Effects of translational and gripping force feedback are decoupled in a 4-degree-of-freedom telemanipulator WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Verner, L. N., Okamura, A. M. 2007: 286-291

  View details for Web of Science ID 000246105200048

• Enhancing transparency of a posit ion-exchange teleoperator WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Mahvash, M., Okamura, A. M. 2007: 470-475

  View details for Web of Science ID 000246105200078

• Evaluation of human performance with kinematic and haptic errors WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Yamamoto, T., Okamura, A. M. 2007: 78-83

  View details for Web of Science ID 000246105200014

• Haptic virtual fixtures for robot-assisted manipulation ROBOTICS RESEARCH Abbott, J. J., Marayong, P., Okamura, A. M. 2007; 28: 49-64

  View details for Web of Science ID 000245915500004

• Dynamic guidance with pseudoadmittance virtual fixtures PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Pezzementi, Z., Okamura, A. M., Hager, G. D. 2007: 1761-1767

  View details for Web of Science ID 000250915301122

• Design of a Pill-Sized 12-legged Endoscopic Capsule Robot. Okamura, A., M., Quirini, M., Webster III, R., J., Menciassi, A., Dario, P. 2007
• Force Sensing in Robot-Assisted Surgery: Which Degrees of Freedom are Most Important? Medicine Meets Virtual Reality (MMVR) 15. Saha, S., Mahvash, M., Verner, L., N., Okamura, A., M. 2007
• Educational Haptics. Grow, D., I., Verner, L., N., Okamura, A., M. 2007
• Electrolytic Silicone Bourdon Tube Microactuator for Reconfigurable Surgical Robots. Okamura, A., M., Pak, N., Ng, Webster III, R., J., Menciassi, A., Dario, P. 2007
• Friction Compensation for Enhancing Transparency of a Teleoperator with Compliant Transmission. IEEE Transactions on Robotics Mahvash, M., Okamura, A., M. 2007; 6 (23): 1240-1246
• Quantifying the value of visual and haptic position feedback during force-based motion control WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Kuchenbecker, K. J., Gurari, N., Okamura, A. M. 2007: 561-562

  View details for Web of Science ID 000246105200096

• Effects of visual and proprioceptive motion feedback on human control of targeted movement 2007 IEEE 10TH INTERNATIONAL CONFERENCE ON REHABILITATION ROBOTICS, VOLS 1 AND 2 Kuchenbecker, K. J., Gurari, N., Okamura, A. M. 2007: 513-524

  View details for Web of Science ID 000255389600077

• Nonholonomic modeling of needle steering INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Webster, R. J., Kim, J. S., Cowan, N. J., Chirikjian, G. S., Okamura, A. M. 2006; 25 (5-6): 509-525

  View details for DOI 10.1177/0278364906065388

  View details for Web of Science ID 000238146600006

• Stable forbidden-region virtual fixtures for bilateral telemanipulation JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME Abbott, J. J., Okamura, A. M. 2006; 128 (1): 53-64

  View details for DOI 10.1115/1.2168163

  View details for Web of Science ID 000236439100007

• Pseudo-admittance bilateral telemanipulation with guidance virtual fixtures SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Abbott, J. J., Okamura, A. M. 2006: 169-175

  View details for Web of Science ID 000237225000027

• Dynamic augmented reality for sensory substitution in robot-assisted surgical systems. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Akinbiyi, T., Reiley, C. E., Saha, S., Burschka, D., Hasser, C. J., Yuh, D. D., Okamura, A. M. 2006; 1: 567-570

  Abstract

  Teleoperated robot-assisted surgical systems provide surgeons with improved precision, dexterity, and visualization over traditional minimally invasive surgery. The addition of haptic (force and/or tactile) feedback has been proposed as a way to further enhance the performance of these systems. However, due to limitations in sensing and control technologies, implementing direct haptic feedback to the surgeon's hands remains impractical for clinical application. A new, intuitive augmented reality system for presentation of force information through sensory substitution has been developed and evaluated. The augmented reality system consists of force-sensing robotic instruments, a kinematic tool tracker, and a graphic display that overlays a visual representation of force levels on top of the moving instrument tips. The system is integrated with the da Vinci Surgical System (Intuitive Surgical, Inc.) and tested by several users in a phantom knot tying task. The augmented reality system decreases the number of broken sutures, decreases the number of loose knots, and results in more consistent application of forces.

  View details for PubMedID 17945986

• Effect of hand dynamics on virtual fixtures for compliant human-machine interfaces* SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Marayong, P., Hager, G. D., Okamura, A. M. 2006: 109-115

  View details for Web of Science ID 000237225000019

• Object Capture With a Camera-Mobile Robot System: An Introductory Robotics Project. IEEE Robotics and Automation Magazine Okamura, A., M., Webster III, R., J. 2006; 1 (13): 85-88
• Portability and applicability of virtual fixtures across medical and manufacturing tasks 2006 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-10 Lin, H. C., Mills, K., Kazanzides, P., Hager, G. D., Marayong, P., Okamura, A. M., Karam, R. 2006: 225-230

  View details for Web of Science ID 000240886900037

• Sensor/Actuator asymmetries in telemanipulators: Implications of partial force feedback SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Verner, L. N., Okamura, A. M. 2006: 309-314

  View details for Web of Science ID 000237225000047

• Toward active cannulas: Miniature snake-like surgical robots 2006 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-12 Webster, R. J., Okamura, A. M., Cowan, N. J. 2006: 2857-2863

  View details for Web of Science ID 000245452403001

• Dynamic augmented reality for sensory substitution in robot-assisted surgical systems 2006 28TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-15 Akinbiyi, T., Reiley, C. E., Saha, S., Burschka, D., Hasser, C. J., Yuh, D. D., Okamura, A. M. 2006: 3090-3093

  View details for Web of Science ID 000247284703142

• Friction compensation for a force-feedback telerobotic system 2006 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-10 Mahvash, M., Okamura, A. M. 2006: 3268-3273

  View details for Web of Science ID 000240886907017

• Friction compensation for a force-feedback teleoperator with compliant transmission PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14 Mahvash, M., Okamura, A. M. 2006: 4508-4513

  View details for Web of Science ID 000252251602110

• Effects of Haptic Feedback on Exploration. Wu, M., Okamura, A., M. 2006
• Environment parameter estimation during bilateral telemanipulation SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Misra, S., Okamura, A. M. 2006: 301-307

  View details for Web of Science ID 000237225000046

• Nonholonomic modeling of needle steering EXPERIMENTAL ROBOTICS IX Iii, R. J., Cowan, N. J., Chirikjian, G., Okamura, A. M. 2006; 21: 35-44

  View details for Web of Science ID 000236887500004

• Effects of position quantization and sampling rate on virtual-wall passivity IEEE TRANSACTIONS ON ROBOTICS Abbott, J. J., Okamura, A. M. 2005; 21 (5): 952-964

  View details for DOI 10.1109/TRO.2005.851377

  View details for Web of Science ID 000232118800015

• Human-machine collaborative systems for microsurgical applications INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Kragic, D., Marayong, P., Li, M., Okamura, A. M., Hager, G. A. 2005; 24 (9): 731-741

  View details for DOI 10.1177/0278364905057059

  View details for Web of Science ID 000232274300005

• Transrectal fiducial carrier for radiographic image registration in prostate Brachytherapy Kemper, J., Burkholder, A., Jain, A., Mustufa, T., Wyrobek, K., Burdette, C., Song, D., Okamura, A., Fichtinger, G. AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS. 2005: 2108-2108

  View details for Web of Science ID 000229908601356

• The snaptic paddle: A modular haptic device WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Wong, C. E., Okamura, A. M. 2005: 537-538

  View details for Web of Science ID 000228426200093

• A velocity-dependent model for needle insertion in soft tissue. Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention Crouch, J. R., Schneider, C. M., Wainer, J., Okamura, A. M. 2005; 8: 624-632

  Abstract

  Models that predict the soft tissue deformation caused by needle insertion could improve the accuracy of procedures such as brachytherapy and needle biopsy. Prior work on needle insertion modeling has focused on static deformation; the experiments presented here show that dynamic effects such as relaxation are important. An experimental setup is described for recording and measuring the deformation that occurs with needle insertion into a soft tissue phantom. Analysis of the collected data demonstrates the time- and velocity-dependent nature of the deformation. Deformation during insertion is shown to be well represented using a velocity-dependent force function with a linear elastic finite element model. The model's accuracy is limited to the period during needle motion, indicating that a viscoelastic tissue model may be required to capture tissue relaxation after the needle stops.

  View details for PubMedID 16686012

• Human-machine collaborative systems for microsurgical applications ROBOTICS RESEARCH Kragic, D., Marayong, P., Li, M., Okamura, A. M., Hager, G. D. 2005; 15: 162-171

  View details for Web of Science ID 000228862600014

• Planning for steerable bevel-tip needle insertion through 2D soft tissue with obstacles 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Alterovitz, R., Goldberg, K., Okamura, A. 2005: 1640-1645

  View details for Web of Science ID 000235460101070

• Automatic detection and segmentation of robot-assisted surgical motions. Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention Lin, H. C., Shafran, I., Murphy, T. E., Okamura, A. M., Yuh, D. D., Hager, G. D. 2005; 8: 802-810

  Abstract

  Robotic surgical systems such as Intuitive Surgical's da Vinci system provide a rich source of motion and video data from surgical procedures. In principle, this data can be used to evaluate surgical skill, provide surgical training feedback, or document essential aspects of a procedure. If processed online, the data can be used to provide context-specific information or motion enhancements to the surgeon. However, in every case, the key step is to relate recorded motion data to a model of the procedure being performed. This paper examines our progress at developing techniques for "parsing" raw motion data from a surgical task into a labelled sequence of surgical gestures. Our current techniques have achieved >90% fully automated recognition rates on 15 datasets.

  View details for PubMedID 16685920

• A fracture mechanics approach to haptic synthesis of tissue cutting with scissors WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Mahvash, M., Okamura, A. M. 2005: 356-362

  View details for Web of Science ID 000228426200050

• Steering flexible needles under Markov motion uncertainty 2005 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Alterovitz, R., Lim, A., Goldberg, K., Chirikjian, G. S., Okamura, A. M. 2005: 120-125

  View details for Web of Science ID 000235632100020

• Effects of velocity on human force control WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Wu, M., Abbott, J. J., Okamura, A. M. 2005: 73-79

  View details for Web of Science ID 000228426200010

• Design considerations for robotic needle steering 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Webster, R. J., Memisevic, J., Okamura, A. M. 2005: 3588-3594

  View details for Web of Science ID 000235460103006

• A velocity-dependent model for needle insertion in soft tissue MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2005, PT 2 Crouch, J. R., Schneider, C. M., Wainer, J., Okamura, A. M. 2005; 3750: 624-632

  View details for Web of Science ID 000233356900077

• Diffusion-based motion planning for a nonholonomic flexible needle model 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Park, W., Kim, J. S., Zhou, Y., Cowan, N. J., Okamura, A. M., Chirikjian, G. S. 2005: 4600-4605

  View details for Web of Science ID 000235460103169

• Effects of gripping and translational forces on teleoperation MULTI-POINT INTERACTION WITH REAL AND VIRTUAL OBJECTS Verner, L. N., Jeung, K. A., Okamura, A. M. 2005; 18: 231-241

  View details for Web of Science ID 000231731400016

• Automatic detection and segmentation of robot-assisted surgical motions MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2005, PT 1 Lin, H. C., Shafran, I., Murphy, T. E., Okamura, A. M., Yuh, D. D., Hager, G. D. 2005; 3749: 802-810

  View details for Web of Science ID 000233337000099

• Effect of sensory substitution on suture-manipulation forces for robotic surgical systems JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY Kitagawa, M., Dokko, D., Okamura, A. M., Yuh, D. D. 2005; 129 (1): 151-158

  Abstract

  Direct haptic (force or tactile) feedback is not yet available in commercial robotic surgical systems. Previous work by our group and others suggests that haptic feedback might significantly enhance the execution of surgical tasks requiring fine suture manipulation, specifically those encountered in cardiothoracic surgery. We studied the effects of substituting direct haptic feedback with visual and auditory cues to provide the operating surgeon with a representation of the forces he or she is applying with robotic telemanipulators.Using the robotic da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, Calif), we compared applied forces during a standardized surgical knot-tying task under 4 different sensory-substitution scenarios: no feedback, auditory feedback, visual feedback, and combined auditory-visual feedback.The forces applied with these sensory-substitution modes more closely approximate suture tensions achieved under ideal haptic conditions (ie, hand ties) than forces applied without such sensory feedback. The consistency of applied forces during robot-assisted suture tying aided by visual feedback or combined auditory-visual feedback sensory substitution is superior to that achieved with hand ties. Robot-assisted ties aided with auditory feedback revealed levels of consistency that were generally equivalent or superior to those attained with hand ties. Visual feedback and auditory feedback improve the consistency of robotically applied forces.Sensory substitution, in the form of visual feedback, auditory feedback, or both, confers quantifiable advantages in applied force accuracy and consistency during the performance of a simple surgical task.

  View details for DOI 10.1016/j.jtcvs.2004.05.029

  View details for Web of Science ID 000226216600021

  View details for PubMedID 15632837

• Vision-assisted control for manipulation using virtual fixtures IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION Bettini, A., Marayong, P., Lang, S., Okamura, A. M., Hager, G. D. 2004; 20 (6): 953-966

  View details for DOI 10.1109/TRO.2004.829483

  View details for Web of Science ID 000225484300003

• Force modeling for needle insertion into soft tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Okamura, A. M., Simone, C., O'Leary, M. D. 2004; 51 (10): 1707-1716

  Abstract

  The modeling of forces during needle insertion into soft tissue is important for accurate surgical simulation, preoperative planning, and intelligent robotic assistance for percutaneous therapies. We present a force model for needle insertion and experimental procedures for acquiring data from ex vivo tissue to populate that model. Data were collected from bovine livers using a one-degree-of-freedom robot equipped with a load cell and needle attachment. computed tomography imaging was used to segment the needle insertion process into phases identifying different relative velocities between the needle and tissue. The data were measured and modeled in three parts: 1) capsule stiffness, a nonlinear spring model; 2) friction, a modified Karnopp model; and 3) cutting, a constant for a given tissue. In addition, we characterized the effects of needle diameter and tip type on insertion force using a silicone rubber phantom. In comparison to triangular and diamond tips, a bevel tip causes more needle bending and is more easily affected by tissue density variations. Forces for larger diameter needles are higher due to increased cutting and friction forces.

  View details for DOI 10.1109/TBME.2004.831542

  View details for Web of Science ID 000224001900002

  View details for PubMedID 15490818

• Speed-accuracy characteristics of human-machine cooperative manipulation using virtual fixtures with variable admittance HUMAN FACTORS Marayong, P., Okamura, A. M. 2004; 46 (3): 518-532

  Abstract

  This work explores the effect of virtual fixture admittance on the performance, defined by error and time, of task execution with a human-machine cooperative system. A desired path is obtained using computer vision, and virtual fixtures for assistance in planar path following were implemented on an admittance-controlled robot. The admittance controller uses a velocity gain, so that the speed of the robot is proportional to the force applied by the operator. The level of virtual fixture guidance is determined by the admittance ratio, which is the ratio of the admittance gain of the force components orthogonal to the path to the gain of the force components parallel to the path. In Experiment 1, we found a linear relationship between admittance ratio and performance. In Experiment 2, we examined the effect of admittance ratio on the performance of three tasks: path following, off-path targeting, and obstacle avoidance. An algorithm was developed to select an appropriate admittance ratio based on the nature of the task. Automatic admittance ratio tuning is recommended for next-generation virtual fixtures. Actual or potential applications of this research include surgery, assembly, and manipulation at the macro and micro scales.

  View details for Web of Science ID 000224978900011

  View details for PubMedID 15573549

• Application of haptic feedback to robotic surgery JOURNAL OF LAPAROENDOSCOPIC & ADVANCED SURGICAL TECHNIQUES-PART A Bethea, B. T., Okamura, A. M., Kitagawa, M., Fitton, T. P., Cattaneo, S. M., Gott, V. L., Baumgartner, W. A., Yuh, D. D. 2004; 14 (3): 191-195

  Abstract

  Robotic surgical systems have greatly contributed to the advancement of minimally invasive endoscopic surgery. However, current robotic systems do not provide tactile or haptic feedback to the operating surgeon. Under certain circumstances, particularly with the manipulation of delicate tissues and suture materials, this may prove to be a significant irritation. We hypothesize that haptic feedback, in the form of sensory substitution, facilitates the performance of surgical knot tying. This preliminary study describes evidence that visual sensory substitution permits the surgeon to apply more consistent, precise, and greater tensions to fine suture materials without breakage during robot-assisted knot tying.

  View details for Web of Science ID 000222276000015

  View details for PubMedID 15245675

• Teleoperation with sensor/actuator asymmetry: Task performance with partial force feedback 12TH INTERNATIONAL SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Semere, W., Kitagawa, M., Okamura, A. M. 2004: 121-127

  View details for Web of Science ID 000189492300016

• Haptic rendering of tissue cutting with scissors MEDICINE MEETS VIRTUAL REALITY 12 Weiss, D. J., Okamura, A. M. 2004; 98: 407-409

  Abstract

  Current surgical simulations that involve cutting with scissors lack display of forces "between the fingers" of the operator. The objective of this work is to develop a fast, realistic haptic rendering technique for scissor cutting that can be easily integrated into soft tissue models commonly used in surgical simulators. A virtual environment was created for combined graphic and haptic display of cutting. Two 2-dimensional deformable mass-spring-damper models were developed: The first is a large mesh that is used to calculate translational forces. The second is a smaller, one-element-thick mesh that is used to calculate cutting (angular) forces. This technique was implemented on the haptic scissors, a haptic interface that allows motion and force feedback in translation and cutting.

  View details for Web of Science ID 000222326200090

  View details for PubMedID 15544316

• The effect of visual and haptic feedback on computer-assisted needle insertion. Computer aided surgery Gerovich, O., Marayong, P., Okamura, A. M. 2004; 9 (6): 243-249

  Abstract

  We present a study evaluating the effects of visual and haptic feedback on human performance in a needle insertion task.A one-degree-of-freedom needle insertion simulator with a three-layer tissue model (skin, fat and muscle) was used in perceptual experiments. The objective of the 14 subjects was to detect the puncture of each tissue layer using varying haptic and visual cues. Performance was measured by overshoot error-the distance traveled by the virtual needle after puncture.Without force feedback, real-time visual feedback reduced error by at least 87% in comparison to static image overlay. Force feedback, in comparison to no force feedback, reduced puncture overshoot by at least 52% when visual feedback was absent or limited to static image overlay. A combination of force and visual feedback improved performance, especially for tissues with low stiffness, by at least 43% with visual display of the needle position, and by at least 67% with visual display of layer deflection.Real-time image overlay significantly enhances controlled puncture during needle insertion. Force feedback may not be necessary except in circumstances where visual feedback is limited.

  View details for PubMedID 16112974

• Performance analysis of steady-hand teleoperation versus cooperative manipulation 12TH INTERNATIONAL SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Emeagwali, I., Marayong, P., Abbott, J. J., Okamura, A. M. 2004: 316-322

  View details for Web of Science ID 000189492300044

• Vision-based assistance for ophthalmic micro-surgery MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2004, PT 2, PROCEEDINGS Dewan, M., Marayong, P., Okamura, A. M., Hager, G. D. 2004; 3217: 49-57

  View details for Web of Science ID 000224322400007

• Effect of sensory substitution on suture manipulation forces for surgical teleoperation MEDICINE MEETS VIRTUAL REALITY 12 Kitagawa, M., Dokko, D., Okamura, A. M., Bethea, B. T., Yuh, D. D. 2004; 98: 157-163

  Abstract

  Bilateral telemanipulation, which applies haptic feedback to the operator, is not yet available in most commercial robot-assisted surgical systems. We have shown in previous work that the lack of haptic (force or tactile) feedback is detrimental in applications requiring fine suture manipulation. In this paper, we study the effect of substituting direct haptic feedback with visual and auditory cues. Using the da Vinci robot from Intuitive Surgical, we observed the difference between applied forces during a knot tying procedure for four different sensory feedback substitution scenarios: no feedback, auditory feedback, visual feedback, and a combination of auditory and visual feedback. Our results indicate that visual feedback, which provides continuous force information, would improve robot-assisted performance during complex surgical tasks such as knot tying with fine sutures. Discrete auditory feedback gives additional useful support to the surgeon.

  View details for Web of Science ID 000222326200037

  View details for PubMedID 15544263

• Methods for haptic feedback in teleoperated robot-assisted surgery INDUSTRIAL ROBOT-AN INTERNATIONAL JOURNAL Okamura, A. M. 2004; 31 (6): 499-508

  View details for DOI 10.1108/01439910410566362

  View details for Web of Science ID 000224825400008

• Virtual remote center of motion control for needle placement robots. Computer aided surgery Boctor, E. M., Webster, R. J., Mathieu, H., Okamura, A. M., Fichtinger, G. 2004; 9 (5): 175-183

  Abstract

  We present an algorithm that enables percutaneous needle-placement procedures to be performed with unencoded, unregistered, minimally calibrated robots while removing the constraint of placing the needle tip on a mechanically enforced Remote Center of Motion (RCM).The algorithm requires only online tracking of the surgical tool and a five-degree-of-freedom (5-DOF) robot comprising three prismatic DOF and two rotational DOF. An incremental adaptive motion control cycle guides the needle to the insertion point and also orients it to align with the target-entry-point line. The robot executes RCM motion without having a physically constrained fulcrum point.The proof-of-concept prototype system achieved 0.78 mm translation accuracy and 1.4 degrees rotational accuracy (this is within the tracker accuracy) within 17 iterative steps (0.5-1 s).This research enables robotic assistant systems for image-guided percutaneous procedures to be prototyped/constructed more quickly and less expensively than has been previously possible. Since the clinical utility of such systems is clear and has been demonstrated in the literature, our work may help promote widespread clinical adoption of this technology by lowering system cost and complexity.

  View details for PubMedID 16192059

• A modular 2-DOF force-sensing instrument for laparoscopic surgery MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2003, PT 1 Prasad, S. K., Kitagawa, M., Fischer, G. S., Zand, J., Talamini, M. A., Taylor, R. H., Okamura, A. M. 2003; 2878: 279-286

  View details for Web of Science ID 000188592600035

• Recognition of operator motions for real-time assistance using virtual fixtures 11TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS - HAPTICS 2003, PROCEEDINGS Ming, L., Okamura, A. M. 2003: 125-131

  View details for Web of Science ID 000182249800017

• The Haptic Scissors: Cutting in virtual environments 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Okamura, A. M., Webster, R. J., Nolin, J. T., Johnson, K. W., Jafry, H. 2003: 828-833

  View details for Web of Science ID 000187419900133

• Virtual fixture architectures for telemanipulation 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Abbott, J. J., Okamura, A. M. 2003: 2798-2805

  View details for Web of Science ID 000187419900449

• Uniting haptic exploration and display ROBOTICS RESEARCH Okamura, A. M. 2003; 6: 225-238

  View details for Web of Science ID 000183013700015

• Robotic needle insertion: Effects of friction and needle geometry 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS O'Leary, M. D., Simone, C., Washio, T., Yoshinaka, K., Okamura, A. M. 2003: 1774-1780

  View details for Web of Science ID 000187419900285

• Steady-hand teleoperation with virtual fixtures RO-MAN 2003: 12TH IEEE INTERNATIONAL WORKSHOP ON ROBOT AND HUMAN INTERACTIVE COMMUNICATION, PROCEEDINGS Abbott, J. J., Hager, G. D., Okamura, A. M. 2003: 145-151

  View details for Web of Science ID 000186827500025

• Methods for intelligent localization and mapping during haptic exploration 2003 IEEE INTERNATIONAL CONFERENCE ON SYSTEMS, MAN AND CYBERNETICS, VOLS 1-5, CONFERENCE PROCEEDINGS Schaeffer, M. A., Okamura, A. M. 2003: 3438-3445

  View details for Web of Science ID 000186578600561

• Virtual remote center of motion control for needle placement robots MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2003, PT 1 Boctor, E. M., Webster, R. J., Mathieu, H., Okamura, A. M., Fichtinger, G. 2003; 2878: 157-164

  View details for Web of Science ID 000188592600020

• Activation cues and force scaling methods for virtual fixtures 11TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS - HAPTICS 2003, PROCEEDINGS Nolin, J. T., Stemniski, P. M., Okamura, A. M. 2003: 404-409

  View details for Web of Science ID 000182249800053

• Analysis of virtual fixture contact stability for telemanipulation IROS 2003: PROCEEDINGS OF THE 2003 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Abbott, J. J., Okamura, A. M. 2003: 2699-2706

  View details for Web of Science ID 000187883300437

• Spatial motion constraints: Theory and demonstrations for robot guidance using virtual fixtures 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Marayong, P., Li, M., Okamura, A. M., Hager, G. D. 2003: 1954-1959

  View details for Web of Science ID 000187419900313

• Measurement, analysis, and display of haptic signals during surgical cutting PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS Greenish, S., Hayward, V., Chial, V., Okamura, A., Steffen, T. 2002; 11 (6): 626-651

  View details for Web of Science ID 000180224100006

• Building a task language for segmentation and recognition of user input to cooperative manipulation systems 10TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Hundtofte, C. S., Hager, G. D., Okamura, A. M. 2002: 225-230

  View details for Web of Science ID 000175458900029

• On the display of haptic recordings for cutting biological tissues 10TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Chial, V. B., Greenish, S., Okamura, A. M. 2002: 80-87

  View details for Web of Science ID 000175458900011

• Vision assisted control for manipulation using virtual fixtures: Experiments at macro and micro scales 2002 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Bettini, A., Lang, S., Okamura, A., Hager, G. 2002: 3354-3361

  View details for Web of Science ID 000178573200530

• Effect of virtual fixture compliance on human-machine cooperative manipulation 2002 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-3, PROCEEDINGS Marayong, P., Bettini, A., Okamura, A. 2002: 1089-1095

  View details for Web of Science ID 000179289100177

• Measurement of the tip and friction force acting on a needle during penetration MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Kataoka, H., Washio, T., Chinzei, K., Mizuhara, K., Simone, C., Okamura, A. M. 2002; 2488: 216-223

  View details for Web of Science ID 000189412100027

• Analysis of suture manipulation forces for teleoperation with force feedback MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Kitagawa, M., Okamura, A. M., Bethea, B. T., Gott, V. L., Baumgartner, W. A. 2002; 2488: 155-162

  View details for Web of Science ID 000189412100020

• The effect of visual and haptic feedback on manual and teleoperated needle insertion MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Gerovichev, O., Marayong, P., Okamura, A. M. 2002; 2488: 147-154

  View details for Web of Science ID 000189412100019

• Modeling of needle insertion forces for robot-assisted percutaneous therapy 2002 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Simone, C., Okamura, A. M. 2002: 2085-2091

  View details for Web of Science ID 000178573200328

• Feature-guided exploration with a robotic finger 2001 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Okamura, A. M., Cutkosky, M. R. 2001: 589-596

  View details for Web of Science ID 000172615800095

• Vision assisted control for manipulation using virtual fixtures IROS 2001: PROCEEDINGS OF THE 2001 IEEE/RJS INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Bettini, A., Lang, S., Okamura, A., Hager, G. 2001: 1171-1176

  View details for Web of Science ID 000176593900187

• Haptic surface exploration EXPERIMENTAL ROBOTICS VI Okamura, A. M., Costa, M. A., Turner, M. L. 2000; 250: 423-432

  View details for Web of Science ID 000086068500041

• Haptic exploration of fine surface features ICRA '99: IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-4, PROCEEDINGS Okamura, A. M., Cutkosky, M. R. 1999: 2930-2936

  View details for Web of Science ID 000081625700464

• Vibration feedback models for virtual environments 1998 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-4 Okamura, A. M., Dennerlein, J. T., Howe, R. D. 1998: 674-679

  View details for Web of Science ID 000074368900107

• Haptic exploration of objects with rolling and sliding Okamura, A. M., Turner, M. L., Cutkosky, M. R. IEEE. 1997: 2485-2490

  View details for Web of Science ID A1997BJ42X00394