Biomedical subjects

Mika N Sinanan

Publications and source records attributed to Mika N Sinanan.

7 recordsLinked to original sources

PubMed2006

Expectant management is safe for cholelithiasis after heart transplant.

BACKGROUND: The optimal management of cholelithiasis after heart transplant remains unclear. We use expectant management based on symptoms, without screening studies or prophylactic treatment. We hypothesized that expectant management for cholelithiasis after heart transplant does not result in significant mortality or morbidity from gallstone-associated disease. METHODS: Between November 1985 and August 2004, 409 heart transplants were performed in 402 recipients at the University of Washington. This is a non-concurrent cohort study of these recipients. RESULTS: Among recipients, 24 underwent cholecystectomy before heart transplant. After transplant, in the remaining 378 patients, 34 were found to have gallstones during the observation period. There was no mortality from gallstone-associated disease. Thirty patients developed morbidity from gallstones, including 25 cases of biliary colic, 3 of acute cholecystitis and 2 of pancreatitis, and there was 1 abnormal liver function test. Acute cholecystitis and pancreatitis were treated with conservative management followed by cholecystectomy. Cholecystectomy was performed in 32 patients after transplant. Indications included symptomatic cholelithiasis in 31, and prophylactic cholecystectomy prior to kidney transplant in 1. The laparoscopic approach was performed in 25 of these 32 patients. There was no mortality from cholecystectomy, but there were 4 complications: surgical site infections (n = 2); wound dehiscence (n = 1); and bile duct injury (n = 1). Median hospital stay was 1 day. CONCLUSIONS: Our expectant management for cholelithiasis after heart transplant resulted in no mortality or significant morbidity related to delay in treatment. Symptomatic cholelithiasis was successfully treated with cholecystectomy, mostly with the laparoscopic approach. We believe expectant management is safe for patients after heart transplant.

Adult↗

PubMed2006

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.

Computer Simulation↗

PubMed2006

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 degrees, 50 degrees). A prototype 6-DOF surgical robot has been developed and will be the subject of further study.

Computer-Aided Design↗

PubMed2006

Hybrid analysis of a spherical mechanism for a minimally invasive surgical (MIS) robot--design concepts for multiple optimizations.

Several criteria exist for determining the optimal design for a surgical robot. This paper considers kinematic performance metrics, which reward good kinematic performance, and dynamic performance metrics, which penalize poor dynamic performance. Kinematic and dynamic metrics are considered independently, and then combined to produce hybrid metrics. For each metric, the optimal design is the one that maximizes the performance metric over a specific design space. In the case of a 2-DOF spherical mechanism for a surgical robot, the optimal design determined by kinematic metrics is a robot arm with link angles (alpha(12)=90 degrees , alpha(23)=90 degrees ). The large link angles are the most dextrous, but have the greatest risk of robot-robot or robot-patient collisions and require the largest actuators. The link lengths determined by the dynamic metrics are much shorter, which reduces the risk of collisions, but tend to place the robot in singularities much more frequently. When the hybrid metrics are used, and a restriction that the arm must be able to reach a human's entire abdomen, the optimal design is around (alpha(12)=51 degrees, alpha(23)=54 degrees). The hybrid design provides a compromise between dexterity and compactness.

Equipment Design↗

PubMed2004

Quantifying surgeon grasping mechanics in laparoscopy using the Blue DRAGON system.

Mechanical testing of abdominal organs has a profound impact on surgical simulation and surgical robotics development. Due to the nonlinear and viscoelastic nature of soft tissue it is crucial to test them in surgically relevant ranges of applied force, deformation, and duration for incorporating haptic realism into surgical simulators and for safe operation of surgical robots. In order to determine these ranges, a system known as the Blue DRAGON was used to track the motions and the forces applied to surgical tools during live procedures for quantifying how surgeons typically perform a minimally invasive surgical procedure. Thirty-one surgeons of varying skill were recorded performing three different surgical tasks. Grasping force (as applied to the tool handles) and handle angle for each tool were the signals of interest among 26 channels total acquired by the system in real time. These data were analyzed for their magnitudes and frequency content. Using the tool contact state, an algorithm selected tissue grasps to analyze measures during grasps only, as well as obtain grasp durations. The mean force applied to the tool handles during tissue grasps was 8.52 N +/- 2.77 N; maximum force was 68.17 N. Ninety-five percent of the handle angle frequency content was below 1.98 Hz +/- 0.98 Hz. Average grasp time was 2.29 s +/- 1.65 s, and 95% of all grasps were held for 8.86 s +/- 7.06 s or less. The average maximum grasp time during these tasks was 13.37 s +/- 11.42 s. These results form the basis for determining how abdominal tissues are to be mechanically tested in ranges and durations of force and deformation that are surgically realistic. Additionally, this information may serve as design specifications for new surgical robots or haptic simulators.

Animals↗

PubMed2004

Optimization of a vector quantization codebook for objective evaluation of surgical skill.

Surgical robotic systems and virtual reality simulators have introduced an unprecedented precision of measurement for both tool-tissue and tool-surgeon interaction; thus holding promise for more objective analyses of surgical skill. Integrative or averaged metrics such as path length, time-to-task, success/failure percentages, etc., have often been employed towards this end but these fail to address the processes associated with a surgical task as a dynamic phenomena. Stochastic tools such as Markov modeling using a 'white-box' approach have proven amenable to this type of analysis. While such an approach reveals the internal structure of the of the surgical task as a process, it requires a task decomposition based on expert knowledge, which may result in a relatively large/complex model. In this work, a 'black box' approach is developed with generalized cross-procedural applications., the model is characterized by a compact topology, abstract state definitions, and optimized codebook size. Data sets of isolated tasks were extracted from the Blue DRAGON database consisting of 30 surgical subjects stratified into six training levels. Vector quantization (VQ) was employed on the entire database, thus synthesizing a lexicon of discrete, task-independent surgical tool/tissue interactions. VQ has successfully established a dictionary of 63 surgical code words and displayed non-temporal skill discrimination. VQ allows for a more cross-procedural analysis without relying on a thorough study of the procedure, links the results of the black-box approach to observable phenomena, and reduces the computational cost of the analysis by discretizing a complex, continuous data space.

Algorithms↗

PubMed2003

In-vivo and in-situ compressive properties of porcine abdominal soft tissues.

Accurate biomechanical characteristics of tissues are essential for developing realistic virtual reality surgical simulators utilizing haptic feedback. Surgical simulation technology has progressed rapidly but lacks a comprehensive database of soft tissue mechanical properties with which to incorporate. Simulators are often designed purely based on what "feels right;" quantitative empirical data are lacking. A motorized endoscopic grasper was used to test abdominal porcine tissues in-vivo and in-situ with cyclic and static compressive loadings. An exponential constitutive equation was fit to the resulting stress-strain curves, and the coefficients were compared for various conditions. Stress relaxation for liver and small bowel were also examined. Differences between successive squeezes and between in-vivo and in-situ conditions were found.

Abdomen↗