Mika N. Sinanan

Force controlled and teleoperated endoscopic grasper for minimally invasive surgery-experimental performance evaluation

Minimally invasive surgery generates new user interfaces which create visual and haptic distortion when compared to traditional surgery. In order to regain the tactile and kinesthetic information that is lost, a computerized force feedback endoscopic surgical grasper (FREG) was developed with computer control and a haptic user interface. The system uses standard unmodified grasper shafts and tips. The FREG can control grasping forces either by surgeon teleoperation control, or under software control. The FREG performance was evaluated using an automated palpation function (programmed series of compressions) in which the grasper measures mechanical properties of the grasped materials. The material parameters obtained from measurements showed the ability of the FREG to discriminate between different types of normal soft tissues (small bowel, lung, spleen, liver, colon, and stomach) and different kinds of artificial soft tissue replication materials (latex/silicone) for simulation purposes. In addition, subjective tests of ranking stiffness of silicone materials using the FREG teleoperation mode showed significant improvement in the performance compared to the standard endoscopic grasper. Moreover, the FREG performance was closer to the performance of the human hand than the standard endoscopic grasper. The FREG as a tool incorporating the force feedback teleoperation technology may provide the basis for application in telesurgery, clinical endoscopic surgery, surgical training, and research.

Markov modeling of minimally invasive surgery based on tool/tissue interaction and force/torque signatures for evaluating surgical skills

The best method of training for laparoscopic surgical skills is controversial. Some advocate observation in the operating room, while others promote animal and simulated models or a combination of surgery-related tasks. A crucial process in surgical education is to evaluate the level of surgical skills. For laparoscopic surgery, skill evaluation is traditionally performed subjectively by experts grading a video of a procedure performed by a student. By its nature, this process uses fuzzy criteria. The objective of the current study was to develop and assess a skill scale using Markov models (MMs). Ten surgeons [five novice surgeons (NS); five expert surgeons (ES)] performed a cholecystectomy and Nissen fundoplication in a porcine model. An instrumented laparoscopic grasper equipped with a three-axis force/torque (F/T) sensor was used to measure the forces/torques at the hand/tool interface synchronized with a video of the tool operative maneuvers. A synthesis of frame-by-frame video analysis and a vector quantization algorithm, allowed to define F/T signatures associated with 14 different types of tool/tissue interactions. The magnitude of F/T applied by NS and ES were significantly different (p<0.05) and varied based on the task being performed. High F/T magnitudes were applied by NS compared with ES while performing tissue manipulation and vice versa in tasks involved tissue dissection. From each step of the surgical procedures, two MMs were developed representing the performance of three surgeons out of the five in the ES and NS groups. The data obtained by the remaining two surgeons in each group were used for evaluating the performance scale. The final result was a surgical performance index which represented a ratio of statistical similarity between the examined surgeons MM and the MM of NS and ES. The difference between the performance index value, for a surgeon under study, and the NS/ES boundary, indicated the level of expertise in the surgeons own group. Preliminary data suggest that a performance index based on MM and F/T signatures provides an objective means of distinguishing NS from ES. In addition, this methodology can be further applied to evaluate haptic virtual reality surgical simulators for improving realism in surgical education.

Generalized approach for modeling minimally invasive surgery as a stochastic process using a discrete Markov model

Minimally invasive surgery (MIS) involves a multidimensional series of tasks requiring a synthesis between visual information and the kinematics and dynamics of the surgical tools. Analysis of these sources of information is a key step in defining objective criteria for characterizing surgical performance. The Blue DRAGON is a new system for acquiring the kinematics and the dynamics of two endoscopic tools synchronized with the endoscopic view of the surgical scene. Modeling the process of MIS using a finite state model [Markov model (MM)] reveals the internal structure of the surgical task and is utilized as one of the key steps in objectively assessing surgical performance. The experimental protocol includes tying an intracorporeal knot in a MIS setup performed on an animal model (pig) by 30 surgeons at different levels of training including expert surgeons. An objective learning curve was defined based on measuring quantitative statistical distance (similarity) between MM of experts and MM of residents at different levels of training. The objective learning curve was similar to that of the subjective performance analysis. The MM proved to be a powerful and compact mathematical model for decomposing a complex task such as laparoscopic suturing. Systems like surgical robots or virtual reality simulators in which the kinematics and the dynamics of the surgical tool are inherently measured may benefit from incorporation of the proposed methodology.

Biomechanical Properties of Abdominal Organs In Vivo and Postmortem Under Compression Loads

Accurate knowledge of biomechanical characteristics of tissues is essential for developing realistic computer-based surgical simulators incorporating haptic feedback, as well as for the design of surgical robots and tools. As simulation technologies continue to be capable of modeling more complex behavior, an in vivo tissue property database is needed. Most past and current biomechanical research is focused on soft and hard anatomical structures that are subject to physiological loading, testing the organs in situ. Internal organs are different in that respect since they are not subject to extensive loads as part of their regular physiological function. However, during surgery, a different set of loading conditions are imposed on these organs as a result of the interaction with the surgical tools. Following previous research studying the kinematics and dynamics of tool/tissue interaction in real surgical procedures, the focus of the current study was to obtain the structural biomechanical properties (engineering stress-strain and stress relaxation) of seven abdominal organs, including bladder, gallbladder, large and small intestines, liver, spleen, and stomach, using a porcine animal model. The organs were tested in vivo, in situ, and ex corpus (the latter two conditions being postmortem) under cyclical and step strain compressions using a motorized endoscopic grasper and a universal-testing machine. The tissues were tested with the same loading conditions commonly applied by surgeons during minimally invasive surgical procedures. Phenomenological models were developed for the various organs, testing conditions, and experimental devices. A property database-unique to the literature-has been created that contains the average elastic and relaxation model parameters measured for these tissues in vivo and postmortem. The results quantitatively indicate the significant differences between tissue properties measured in vivo and postmortem. A quantitative understanding of how the unconditioned tissue properties and model parameters are influenced by time postmortem and loading condition has been obtained. The results provide the material property foundations for developing science-based haptic surgical simulators, as well as surgical tools for manual and robotic systems.

The RAVEN: Design and Validation of a Telesurgery System

The collaborative effort between fundamental science, engineering and medicine provides physicians with improved tools and techniques for delivering effective health care. Minimally invasive surgery (MIS) techniques have revolutionized the way a number of surgical procedures are performed. Recent advances in surgical robotics are once again revolutionizing MIS interventions and open surgery. In an earlier research endeavor, 30 surgeons performed 7 different MIS tasks using the Blue Dragon system to collect measurements of position, force, and torque on a porcine model. This data served as the foundation for a kinematic optimization of a spherical surgical robotic manipulator. Following the optimization, a seven-degree-of-freedom cable-actuated surgical manipulator was designed and integrated, providing all degrees of freedom present in manual MIS as well as wrist joints located at the surgical end-effector. The RAVEN surgical robot system has the ability to teleoperate utilizing a single bi-directional UDP socket via a remote master device. Preliminary telesurgery experiments were conducted using the RAVEN. The experiments illustrated the system’s ability to operate in extreme conditions using a variety of network settings.

Optimization of a spherical mechanism for a minimally invasive surgical robot: theoretical and experimental approaches

With a focus on design methodology for developing a compact and lightweight minimally invasive surgery (MIS) robot manipulator, the goal of this study is progress toward a next-generation surgical robot system that will help surgeons deliver healthcare more effectively. Based on an extensive database of in-vivo surgical measurements, the workspace requirements were clearly defined. The pivot point constraint in MIS makes the spherical manipulator a natural candidate. An experimental evaluation process helped to more clearly understand the application and limitations of the spherical mechanism as an MIS robot manipulator. The best configuration consists of two serial manipulators in order to avoid collision problems. A complete kinematic analysis and optimization incorporating the requirements for MIS was performed to find the optimal link lengths of the manipulator. The results show that for the serial spherical 2-link manipulator used to guide the surgical tool, the optimal link lengths (angles) are (60/spl deg/, 50/spl deg/). A prototype 6-DOF surgical robot has been developed and will be the subject of further study.

A technique for laparoscopic-assisted percutaneous drainage of infected pancreatic necrosis and pancreatic abscess

Background: Percutaneous drainage has been shown to be an acceptable method for treating both pancreatic abscesses and infected pancreatic necrosis. However, percutaneous techniques have certain shortcomings, including the time and labor required and failure of the catheters to adequately drain the particulate debris. Growing experience around the world indicates that there is a role for retroperitoneal laparoscopy as a means of facilitating the percutaneous drainage of infected pancreatic fluid collections and avoiding a laparotomy. Our technique is discussed in this paper. Methods: Once infection is documented in a pancreatic fluid collection by fine-needle aspiration, one or more percutaneous drains are placed into the fluid collection(s). A computed tomography (CT) scan is repeated. If further drainage is indicated, retroperitoneoscopic debridement is performed. Using a combination of the percutaneous drain(s) and the post-drain CT scan, ports are placed and retroperitoneoscopic debridement of the necrosectum is performed under direct visualization. Prior to completion of the operation, a postoperative lavage system is created. Results: Six patients with infected pancreatic necrosis have been treated with this technique. Prior to commencement of our laparoscopic protocol, all six patients would have required open necrosectomy. Four of the six patients were managed with retroperitoneoscopic debridement and catheter drainage alone. Complications included a colocutaneous fistula and a small flank hernia. There were no bleeding complications and no deaths. Conclusion: Although open necrosectomy remains the standard of care for the treatment of infected pancreatic necrosis and pancreatic abscess, there is growing evidence that laparoscopic retroperitoneal debridement is feasible.

The BlueDRAGON - a system for measuring the kinematics and dynamics of minimally invasive surgical tools in-vivo

Minimally invasive surgery involves a multidimensional series of tasks requiring a synthesis between visual information and the kinematics and dynamics of the surgical tools. Analysis of these sources of information is a key step in mastering MIS, but may also be used to define objective criteria for characterizing surgical performance. The BlueDRAGON is a new system for acquiring the kinematics and dynamics of two endoscopic tools synchronized with the visual view of the surgical scene. It includes two four-bar passive mechanisms equipped with position and force torque sensors for measuring the positions and orientations of the two endoscopic tools along with the forces and torques (F/T) applied by the surgeons hands. The methodology of decomposing the surgical task is based on a fully connected, 28 finite-states Markov model where each states corresponded to a fundamental tool/tissue interaction based on the tool kinematics and associated with unique F/T signatures. The experimental protocol includes seven MIS tasks performed on an animal model by 30 surgeons at different levels of their residency training including expert surgeons. From the preliminary analysis of these data, the major differences between residents at different skill levels are discussed. Systems like surgical robots or virtual reality simulators that inherently measure the kinematics and dynamics of the surgical tool may benefit from inclusion of the proposed methodology for the analysis of efficacy and objective evaluation of surgical skills during training.

Skills Evaluation in Minimally Invasive Surgery Using Force/Torque Signatures

AbstractBackground: One of the more difficult tasks in surgical education is to teach the optimal application of instrument forces and torques necessary to facilitate the conduct of an operation. For laparoscopic surgery, this type of training has traditionally taken place in the operating room, reducing operating room efficiency and potentially affecting the safe conduct of the operation. The objective of the current study was to measure and compare forces and torques (F/T) applied at the tool/hand interface generated during laparoscopic surgery by novice (NS) and experienced (ES) surgeons using an instrumented laparoscopic grasper and to use this data for evaluating the skill level. Methods: Ten surgeons (five-NS, five-ES) performed a cholecystectomy and Nissen fundoplication in a porcine model. An instrumented laparoscopic grasper with interchangeable standard surgical tips equipped with a three-axis F/T sensor located at the proximal end of the grasper tube was used to measure the F/T at the hand/tool interface. In addition, one axis force sensor located at the graspers handle was used to measure the grasping force. F/T data synchronized with visual view of the tool operative maneuvers were collected simultaneously via a novel graphic user interface incorporated picture-in-picture video technology. Subsequent frame-by-frame video analysis of the operation allowed a definition of states associated with different tool/tissue interactions within each step of the operation. F/T measured within each state were further analyzed using vector quantization (VQ). The VQ analysis defines characteristic sets of F/T in the database that were defined as F/T signature. Results: The magnitude of F/T applied by NS and ES were significantly different (p < 0.05) and varied based on the task being performed. Higher F/T magnitudes were applied by NS than by ES when performing tissue manipulation, whereas lower F/T magnitudes were applied by NS than by ES during tissue dissection. Furthermore, the time to complete the surgical procedure was longer for NS by a factor of 1.5–4.8 when compared to the time for ES. State analysis suggests that most of this time is consumed in an [idle] state, in which movements of the surgeon make no tissue contact. Conclusions: Preliminary data suggest that F/T magnitudes associated with the tool/tissue interactions provide an objective means of distinguishing novices from skilled surgeons. Clinical F/T analysis using the proposed technology and methodology may be helpful in training, developing surgical simulators, and measuring technical proficiency during laparoscopic surgery.

Safety and efficacy of video-assisted retroperitoneal debridement for infected pancreatic collections: a multicenter, prospective, single-arm phase 2 study.

BACKGROUND The feasibility of video-assisted retroperitoneal debridement (VARD) for infected pancreatic walled-off necrosis is established. We provide prospective data on the safety and efficacy of VARD. DESIGN Multicenter, prospective, single-arm phase 2 study. SETTING Six academic medical centers. PATIENTS We evaluated 40 patients with pancreatic necrosis who had infection determined using Gram stain or culture. INTERVENTIONS Percutaneous drains were placed at enrollment, and computed tomographic scans were repeated at 10 days. Patients who had more than a 75% reduction in collection size were treated with drains. Other patients were treated with VARD. Crossover to open surgery was performed for technical reasons and/or according to surgeon judgment. MAIN OUTCOME MEASURES Efficacy (ie, successful VARD treatment without crossover to open surgery or death) and safety (based on mortality and complication rates). Patients received follow-up care for 6 months. RESULTS We enrolled 40 patients (24 men and 16 women) during a 51-month period. Median age was 53 years (range, 32-82 years). Mean (SD) Acute Physiology and Chronic Health Evaluation II score at enrollment was 8.0 (5.1), and median computed tomography severity index score was 8. Of the 40 patients, 24 (60%) were treated with minimally invasive intervention (drains with or without VARD). Nine patients (23%) did not require surgery (drains only). For 31 surgical patients, VARD was possible in 60% of patients. Most patients (81%) required 1 operation. In-hospital 30-day mortality was 2.5% (intent-to-treat). Bleeding complications occurred in 7.5% of patients; enteric fistulas occurred in 17.5%. CONCLUSIONS This prospective cohort study supports the safety and efficacy of VARD for infected pancreatic walled-off necrosis. Of the patients, 85% were eligible for a minimally invasive approach. We were able to use VARD in 60% of surgical patients. The low mortality and complication rates compare favorably with open debridement. An unexpected finding was that a reduction in collection size of 75% according to the results of computed tomographic scans at 10 to 14 days predicted the success of percutaneous drainage alone.