R.V. Patel

The University of Western Ontario, London, Ontario, Canada

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Publications (253)162.61 Total impact

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  • Ali Talasaz, R.V. Patel
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    ABSTRACT: Tactile sensing and force reflection have been the subject of considerable research for tumor localization in soft-tissue palpation. The work presented in this paper investigates the relevance of force feedback (presented visually as well as directly) during tactile sensing (presented visually only) for tumor localization using an experimental setup close to one that could be applied for real robotics-assisted minimally invasive surgery. The setup is a teleoperated (master-slave) system facilitated with a state-of-the-art minimally invasive probe with a rigidly mounted tactile sensor at the tip and an externally mounted force sensor at the base of the probe. The objective is to capture the tactile information and measure the interaction forces between the probe and tissue during palpation and to explore how they can be integrated to improve the performance of tumor localization. To quantitatively explore the effect of force feedback on tactile sensing tumor localization, several experiments were conducted by human subjects to locate artificial tumors embedded in the ex vivo bovine livers. The results show that using tactile sensing in a force-controlled environment can realize, on average, 57 percent decrease in the maximum force and 55 percent decrease in the average force applied to tissue while increasing the tumor detection accuracy by up to 50 percent compared to the case of using tactile feedback alone. The results also show that while visual presentation of force feedback gives straightforward quantitative measures, improved performance of tactile sensing tumor localization is achieved at the expense of longer times for the user. Also, the quickness and intuitive data mapping of direct force feedback makes it more appealing to experienced users.
    IEEE Transactions on Haptics 04/2013; 6(2):217-228. · 2.03 Impact Factor
  • A. Talasaz, R.V. Patel
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    ABSTRACT: This work is aimed at developing a new minimally invasive approach to characterize tissue properties in real time during telerobotic palpation and to localize tissue abnormality while estimating its depth. This method relies on using a minimally invasive probe with a rigidly mounted tactile sensor at the tip to capture the force distribution map and the indentation depth by each tactile element and thereby generating a stiffness map for the palpated tissue. The hybrid impedance control technique is used for this approach to enable the operator to switch between position control and force control and thereby to autonomously obtain the required information from the remote tissue. The operator would then be able to localize tissue abnormality based on the force distribution map, the tissue stiffness map and the indentation depth which are visually presented to him/her in real time. This method also enables the operator to estimate the depth at which the tissue abnormality is located. Our results show that tactile sensing alone may be unable to detect tumors embedded deep inside tissue and may also not be a good alternative for palpation on uneven tissue surfaces.
    Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on; 01/2013
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    ABSTRACT: The problem of designing of a haptics-enabled teleoperated rehabilitation system in the presence of communication delays is addressed. In a teleoperated rehabilitation system, communication delays introduce phase shift which may result in the task inversion phenomenon. To overcome the task inversion, a new type of projection-based force reflection algorithm is proposed which is suitable for assistive/resistive therapy in the presence of irregular communication delays. Additionally, algorithms for augmented therapy are introduced which combine the projection-based force reflection with a delay-free local virtual therapist. A small-gain design is developed which guarantees stability of the proposed schemes for both assistive and resistive modes of the therapy. Simulations and experimental results are presented which confirm the improvement achieved by the proposed methods.
    Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on; 01/2013
  • M. Khoshnam, A. Yurkewich, R.V. Patel
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    ABSTRACT: The increasing popularity of catheter-based ablation therapy in treating cardiac arrhythmia has motivated researchers to seek new techniques to improve the accuracy and efficiency of such procedures. After guiding the catheter through the vessels into the heart chambers, precise positioning of the catheter tip and consistent tool/tissue contact force are the two factors that greatly affect the ablation outcome. Implementing force/position control of the catheter tip will improve the efficacy of cardiac ablation procedures immensely. This paper proposes a model-based force control system to ensure a desired contact force at the distal tip, without directly measuring the force applied at the tip. In this regard, it is studied how the displacement of the proximal handle of a common 7-Fr pull-wire ablation catheter relates to the change of angle at its distal tip. The resulting mapping together with a mapping that relates the forces at the distal tip to the tip shape are used in developing a control system that ensures a desired contact force at the tip. This paper also introduces an optical strain sensor that can be used without modification in the manufacture of present day ablation catheters. This strain sensor completes the feedback loop of the control system through integration with the shape to force model. Performance of the control system is evaluated experimentally and the results suggest that model-based control of steerable catheters is feasible for catheter ablation. The proposed control system can be employed on a conventional ablation catheter following a fairly simple calibration step.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: The reduced access conditions present in Minimally Invasive Surgery (MIS) affect the feel of interaction forces between the instruments and the tissue being treated. This loss of haptic information compromises the safety of the procedure and must be overcome through training. Determining the skill level of trainees is critical for ensuring patient safety. The objective of this work was to evaluate the usefulness of force information for skills assessment during MIS. Experiments were performed using a set of sensorized instruments capable of measuring instrument position and tissue interaction forces. The results show that experience level has a strong correlation with force-based metrics. The proposed metrics can be automatically computed, are completely objective, and measure important aspects of performance.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
  • M. Shahbazi, S.F. Atashzar, R.V. Patel
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    ABSTRACT: This paper proposes a teleoperated dual-user system incorporating Virtual Fixtures (VFs) that allows concurrent performance of a robotic surgical task by an expert and a trainee. In order to guide the trainee through the procedure, an adaptive VF is created in the trainee's workspace according to the motion generated by the expert who is performing the surgery at the same time. The VF gets adaptively adjusted based on the level of expertise the trainee shows during the surgery. In addition, the trainee's level of expertise is used to adaptively adjust the dual-user dominance factor in an online fashion, which gives the trainee some authority over the task based on his/her skill level. To quantify the trainee's expertise level, a performance measure is proposed, based on the force generated by the VF. Three performance measures from the literature are also used. To satisfy the desired objectives of the proposed system, an impedance-based control methodology is adopted. Stability of the closed-loop system is investigated using the small-gain theorem. A sufficient stability condition is derived that guarantees stability in the presence of time-varying communication delay. Experimental results are given to validate the performance of the system.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
  • M. Khoshnam, R.V. Patel
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    ABSTRACT: Over the past few decades, catheter-based cardiac ablation has been the first surgical option for treatment of arrhythmia. In order to have an effective ablation procedure, after positioning the catheter at the desired location inside the heart chamber, a consistent tip/tissue contact should be maintained during the whole procedure. With the goal of implementing hybrid force/position control of the catheter tip during the ablation procedure, this paper studies how the catheter tip deflects when forces are applied. A pseudo-rigid-body 3R model for the catheter tip is introduced. The model performance is evaluated through extensive experiments and it is shown that the proposed model can estimate the shape of the bending section of the ablation catheter if force information is available. This model does not require extensive knowledge of the catheter internal structure. Moreover, the well-established static equations are simple to understand and solve, making this model a convenient choice for developing a control system.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In this paper, a vibration-assisted needle insertion technique has been proposed in order to reduce needle-tissue friction. The LuGre friction model was employed as a basis for the current study and the model was extended and analyzed to include the impact of high-frequency vibration on translational friction. Experiments were conducted to evaluate the role of insertion speed as well as vibration frequency on frictional effects. In the experiments conducted, an 18 GA brachytherapy needle was vibrated and inserted into an ex-vivo soft tissue sample using a pair of amplified piezoelectric actuators. Analysis demonstrates that the translational friction can be reduced by introducing a vibratory low-amplitude motion onto a regular insertion profile, which is usually performed at a constant rate.
    Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on; 01/2013
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    ABSTRACT: In this paper, a robotic solution is proposed to deal with the challenges caused by lung motion during needle insertion. To accomplish this goal, a macro-micro robotic tool is designed to compensate for tissue motion using the macro part, while performing the needle insertion independently with the micro part. The main application of this work is for robotics-assisted lung tumor biopsy, where the combined motions of respiration and heartbeat may compromise success. An impedance-based controller keeps the macro reference coordinate in contact with the moving soft tissue using measurements from small pressure sensors mounted at the tip of the macro shaft. The micro part, mounted at the end of the macro robot, manipulates the needle in the harmonized reference coordinate system. Preoperative identification of ex vivo soft tissue is performed to estimate the dynamic behavior of the tissue. The controller is then synthesized based on the identified model. The effects of identification error and high frequency uncertainty are addressed in the control design. A prototype was built to evaluate the proposed approach using: 1) two Mitsubishi PA-10 robots, one for manipulating the macro part and the other for mimicking tissue motion, 2) one motorized linear stage to handle the micro part, and 3) a Phantom Omni haptic device for remote manipulation. Experimental results demonstrate the performance of the motion compensation system.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In this study, kinematic characteristics of writing are compared in 5 patients with writer's cramp who performed a set of standardized writing tasks. The kinematic characteristics include upper limb joint angles, vertical hand pressure, and finger grip force. The effect of writing on different inclined supporting surfaces is also investigated. Our results indicate that altering upper limb posture using inclined surfaces improves aspects of writing discomfort in writer's cramp subjects. Although the change in arm joint angles and fingers/hand pressure is not generalizable between patients, such kinematic evaluations seem to be a key factor in the outcome of any personalized treatment or rehabilitation strategy.
    Neural Engineering (NER), 2013 6th International IEEE/EMBS Conference on; 01/2013
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    ABSTRACT: Writer's cramp, a task specific dystonia is felt to be a disorder of sensorimotor integration involving the basal ganglia and cortex. Motivated by this fact, in the present study we investigated the effects of haptic and visual sensory inputs on cramp severity and frequency during a trial. For this goal seven subjects with writer's cramp disease were asked to perform the trial, which included writing, hovering, and spiral/sinusoidal drawing subtasks. The trial had three major steps namely: A) normal writing, when the patients write without sensory manipulation, B) robotics-assisted writing, when a haptic device supports the pen and provides a compliant writing surface with the goal of manipulating the kinesthetic haptic input, and C) blindfolded writing, when the patients were asked to write while being blindfolded, with the goal of analyzing the potential effects of vision feedback in sensorimotor integration pathway. The number of cramps that occurred and subjective measures of patient feedback about cramp severity were analyzed. The results show that reducing the writing surface rigidity, and blocking vision feedback while writing, changes the cramp pattern and decreases the overall cramp severity.
    Neural Engineering (NER), 2013 6th International IEEE/EMBS Conference on; 01/2013
  • A. Saxena, R.V. Patel
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    ABSTRACT: Involuntary motions of the hand can have a significant deteriorating effect on the performance of microsurgical procedures such as vitreoretinal microsurgery. The most common source of the involuntary motions is physiological tremor. Real-time compensation of physiological tremor is therefore necessary to assist surgeons to accurately perform a microsurgery. A novel approach based on the use of Ionic Polymer Metallic Composites (IPMCs) has been developed for actively compensating physiological tremor in the hand. We present the design of our novel handheld device that compensates for tremor using an IPMC-based actuator. We then experimentally evaluate the device to show the amount of compensation achieved.
    Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on; 01/2013
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    ABSTRACT: The projection-based force reflection (PBFR) algorithms were previously demonstrated to substantially improve stability characteristics of the force reflecting teleoperator systems and haptic interfaces without transparency deterioration in the steady state; however, the transient response of the PFBR algorithms suffers from relatively slow force convergence. In particular, the high frequency component of the contact force, which is very important for the haptic perception of stiff surfaces, is typically filtered out. In this paper, a solution to this problem is proposed which is based on the idea to separate different frequency bands in the force reflection signal and consequently apply the projection-based principle to the low-frequency component, while reflecting the high-frequency component directly. It is shown that, for bilateral teleoperators with irregular communication delays, stability can always be achieved by implementing the above described force reflection scheme, if the cut-off frequency of the complementary filters is sufficiently high and a certain weighting coefficient in the force reflection algorithm is sufficiently low. Experimental results demonstrate that substantial simultaneous improvement of stability and transparency is achieved using the proposed method.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
  • Ran Xu, A. Asadian, A.S. Naidu, R.V. Patel
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    ABSTRACT: Concentric-tube robots can offer dexterous positioning even in a small constrained environment. This technology turns out to be beneficial in many classes of minimally invasive procedures. However, one of the barriers to the practical use of a concentric-tube robot is the design of a real-time control scheme. In previous work by the authors, a computationally efficient torsionally compliant kinematic model of a concentric-tube robot was developed. Using this computationally fast technique and deriving the robot's Jacobian, a new position control approach is proposed in this paper. This mechanism provides computational efficiency as well as good tracking accuracy. To evaluate the performance, experiments were conducted, and the results obtained demonstrate the feasibility of enabling the robot's tip to perform trajectory tracking in real time.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In this paper, a multi-master/single-slave (MM/SS) teleoperated system is discussed. The desired objectives for the MM/SS system include both cooperative and training applications, such as surgical teleoperation and surgical training. An impedance-based control methodology is developed to satisfy the desired objectives of the MM/SS system in the presence of unknown communication delay. The developed methodology is an extension of a structure previously proposed for a dual-user system. To analysis stability of the closed-loop system, the small-gain theorem is used. The proposed stability procedure gives a sufficient condition to guarantee stability of the system in the presence of time delays. Experimental results performed on an MM/SS system with two operators communicating through the Internet demonstrate the validity of the proposed scheme.
    ASME 2012 5th Annual Dynamic Systems and Control Conference joint with the JSME 2012 11th Motion and Vibration Conference; 10/2012
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    ABSTRACT: Traditional surgical approaches for repairing diseased mitral valves have relied on placing the patient on cardiopulmonary bypass (on pump), stopping the heart and accessing the arrested heart directly. However, because this approach has the potential for adverse neurological, vascular and immunological sequalae, less invasive beating heart alternatives are desirable. Emerging beating heart techniques have been developed to offer high-risk patients mitral valve repair using ultrasound guidance alone without stopping the heart. This paper describes the first porcine trials of the NeoChord DS1000 (Minnetonka, MN), employed to attach neochordae to a mitral valve leaflet using the traditional ultrasound guided protocol augmented by dynamic virtual geometric models. The distance errors of the tracked tool tip from the intended midline trajectory (5.2±2.4mm vs. 16.8±10.9mm, p=0.003), navigation times (16.7±8.0s vs. 92.0±84.5s, p=0.004) and total path lengths (225.2±120.3mm vs. 1128.9±931.1mm, p=0.003) were significantly shorter in the augmented ultrasound compared to navigation with ultrasound alone,1 indicating a substantial improvement in the safety and simplicity of the procedure.
    IEEE Transactions on Biomedical Engineering 10/2012; · 2.23 Impact Factor
  • H Azimian, R V Patel, M D Naish, B Kiaii
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    ABSTRACT: In this paper, a computational framework for patient-specific preoperative planning of Robotics-Assisted Minimally Invasive Cardiac Surgery (RAMICS) is presented. It is expected that preoperative planning of RAMICS will improve the success rate by considering robot kinematics, patient-specific thoracic anatomy, and procedure-specific intraoperative conditions. Given the significant anatomical features localized in the preoperative computed tomography images of a patients thorax, port locations and robot orientations (with respect to the patients body coordinate frame) are determined to optimize qualities such as dexterity, reachability, tool approach angles and maneuverability. To address intraoperative geometric uncertainty, the problem is formulated as a Generalized Semi-Infinite Program (GSIP) with a convex lower-level problem to seek a plan that is less sensitive to geometric uncertainty in the neighborhood of surgical targets. It is demonstrated that with a proper formulation of the problem, the GSIP can be replaced by a tractable constrained nonlinear program that uses a multi-criteria objective function to balance between the nominal task performance and robustness to collisions and joint limit violations. Finally, performance of the proposed formulation is demonstrated by a comparison between the plans generated by the algorithm and those recommended by an experienced surgeon for several case studies.
    IEEE transactions on information technology in biomedicine: a publication of the IEEE Engineering in Medicine and Biology Society 09/2012; · 1.69 Impact Factor
  • R Xu, R V Patel
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    ABSTRACT: Concentric-tube robots have the potential to become an important surgical tool for robot-assisted percutaneous interventions. They can provide dexterous operation in a small constrained environment. The kinematic model of a concentric-tube robot has been well developed in terms of accuracy, but the computational cost places limitations on real-time implementation. In this paper, we propose a new technique that will substantially improve the computational efficiency of evaluating the kinematics of a concentric-tube robot in the context of developing a control strategy without sacrificing the accuracy of the results. In this paper we develop a torsionally compliant kinematic model using global variables. The model is validated by comparing the results obtained by computing the kinematic model corresponding to an experimental setup of a concentric-tube robot to which a force/torque sensor has been mounted at its base with those obtained directly from the experimental setup. The results indicate that it is feasible to compute the kinematics of the concentric-tube robot fast enough to allow the position/force control loop to be implemented at a rate of 1 kHz.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:904-7.

Publication Stats

2k Citations
162.61 Total Impact Points

Institutions

  • 1999–2011
    • The University of Western Ontario
      • Department of Electrical and Computer Engineering
      London, Ontario, Canada
  • 2008–2010
    • Lawson Health Research Institute
      London, Ontario, Canada
    • Harvard University
      • School of Engineering and Applied Sciences
      Cambridge, MA, United States
  • 2005–2010
    • London Health Sciences Centre
      London, Ontario, Canada
    • National Research Council Canada
      Ottawa, Ontario, Canada
  • 1999–2007
    • Amirkabir University of Technology
      • Department of Electrical Engineering
      Tehrān, Ostan-e Tehran, Iran
  • 1985–2007
    • Concordia University Montreal
      • Department of Electrical and Computer Engineering
      Montréal, Quebec, Canada
  • 2006
    • University of Ontario Institute of Technology
      Oshawa, Ontario, Canada
  • 1992
    • McGill University
      • Department of Mechanical Engineering
      Montréal, Quebec, Canada
  • 1988–1989
    • Wright State University
      • Department of Electrical Engineering
      Dayton, OH, United States