Split and Join: An Efficient Approach for Simulating Stapled Intestinal Anastomosis in Virtual Reality

Colorectal cancer is a life-threatening disease. It is the second leading cause of cancer-related deaths in the United States. Stapled anastomosis is a rapid treatment for colorectal cancer and other intestinal diseases and has become an integral part of routine surgical practice. However, to the best of our knowledge, there is no existing work simulating intestinal anastomosis that often involves sophisticated soft tissue manipulations such as cutting and stitching. In this paper, for the first time, we propose a novel split and join approach to simulate a side-to-side stapled intestinal anastomosis in virtual reality. We mimic the intestine model using a new hybrid representation—a grid-linked particles model for physics simulation and a surface mesh for rendering. The proposed split and join operations handle the updates of both the grid-linked particles model and the surface mesh during the anastomosis procedure. The simulation results demonstrate the feasibility of the proposed approach in simulating intestine models and the side-to-side anastomosis operation

Quantum Relaxation Method for Linear Systems in Finite Element Problems

Quantum linear system algorithms (QLSAs) for gate-based quantum computing can provide exponential speedups for linear systems of equations. The growth of the condition number with problem size for a system of equations arising from a finite element discretization inhibits the direct application of QLSAs for a speedup. Furthermore, QLSAs cannot use an approximate solution or initial guess to output an improved solution. Here, we present Quantum Relaxation for Linear System (qRLS), as an iterative approach for gate-based quantum computers by embedding linear stationary iterations into a larger block linear system. The block linear system is positive-definite and its condition number scales linearly with the number of iterations independent of the size and condition number of the original system, effectively managing the condition number of the finite element problem. The well-conditioned system enables a practical iterative solution of finite element problems using the state-of-the-art Quantum Signal Processing (QSP) variant of QLSAs. Using positive-definite QLSAs l iterations can be performed in O(\sqrt{l}) time, which is unattainable on classical computers. The complexity of the iterations scales favorably compared to classical architectures due to solution time scaling independent of system size with O(\log(N)) qubits, an exponential improvement opening a new paradigm for iterative finite element solutions on quantum hardware

On the development of an efficient truly meshless discretization procedure in computational mechanics

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaves 157-163).The objective of this thesis is to present an efficient and reliable meshless computational technique - the method of finite spheres - for the solution of boundary value problems on complex domains. This method is truly meshless in the sense that the approximation spaces are generated and the numerical integration is performed without a mesh. While the theory behind meshless techniques is rather straightforward, the generation of a computationally efficient scheme is quite difficult. Computational efficiency may be achieved by proper choice of the interpolation functions, effective ways of incorporating the essential boundary conditions and efficient and specialized numerical integration rules. The pure displacement formulation is observed to exhibit volumetric "locking" during incompressible (or nearly incompressible) analysis. A displacement/pressure mixed formulation is developed to overcome this problem. The stability and optimality of the mixed formulation are tested using numerical inf-sup tests for a variety of discretization schemes. Solutions to several example problems are presented showing the application of the method of finite spheres to problems in solid and fluid mechanics. A very specialized application of the technique to physically based real time medical simulations in multimodal virtual environments is also presented. In the current form of implementation, the method of finite spheres is about five times slower than the finite element techniques for problems in two-dimensional elastostatics.by Suvranu De.Sc.D

Pre-clinical Training for New Notes Procedures: From Ex-vivo Models to Virtual Reality Simulators

Natural orifice transluminal endoscopic surgery (NOTES) is a newer field of endoscopic surgery that allows for scarless treatment of pathologic entities, using novel transluminal approaches. There has been a shift of focus from a clinical and research standpoint from the development and dissemination of "first-generation" NOTES procedures to "new NOTES" procedures that traverse the mucosa of luminal structures, yet do not stray far into the peritoneal cavity. It has been a challenge to find appropriate and effective ways to train gastroenterologists and surgeons in these novel approaches. We review the importance of simulation in training and discuss available simulation options

One-shot domain adaptation in video-based assessment of surgical skills

Deep Learning (DL) has achieved automatic and objective assessment of surgical skills. However, DL models are data-hungry and restricted to their training domain. This prevents them from transitioning to new tasks where data is limited. Hence, domain adaptation is crucial to implement DL in real life. Here, we propose a meta-learning model, A-VBANet, that can deliver domain-agnostic surgical skill classification via one-shot learning. We develop the A-VBANet on five laparoscopic and robotic surgical simulators. Additionally, we test it on operating room (OR) videos of laparoscopic cholecystectomy. Our model successfully adapts with accuracies up to 99.5% in one-shot and 99.9% in few-shot settings for simulated tasks and 89.7% for laparoscopic cholecystectomy. For the first time, we provide a domain-agnostic procedure for video-based assessment of surgical skills. A significant implication of this approach is that it allows the use of data from surgical simulators to assess performance in the operating room.Comment: 12 pages (+9 pages of Supplementary Materials), 4 figures (+2 Supplementary Figures), 2 tables (+5 Supplementary Tables

Stability of self-interstitial atoms in hcp-Zr

a b s t r a c t This paper reports the relative stability of various configurations of self-interstitial atoms (SIAs) in hcp-Zr, based on density-functional-theory calculations. In contrast to literature reports of confusing and sometimes contradicting results based on smaller calculation cells, the results here are from calculation cells that contain more than 180 atoms, and provide the most accurate and reliable prediction of the relative stability of SIAs in hcp-Zr. At the most stable configuration of basal octahedral, the formation energy of SIA is 2.73 eV, which does not change with further increase of calculation cell size. The accurate determination of the stability sequence of different SIA configurations provides key material property knowledge in understanding the microstructure evolution of the zirconium-based cladding material in nuclear reactor systems, especially for the anisotropic diffusion of the radiation-induced point defects

A task and performance analysis of endoscopic submucosal dissection (ESD) surgery

BACKGROUND: ESD is an endoscopic technique for en bloc resection of gastrointestinal lesions. ESD is a widely-used in Japan and throughout Asia, but not as prevalent in Europe or the US. The procedure is technically challenging and has higher adverse events (bleeding, perforation) compared to endoscopic mucosal resection. Inadequate training platforms and lack of established training curricula have restricted its wide acceptance in the US. Thus, we aim to develop a Virtual Endoluminal Surgery Simulator (VESS) for objective ESD training and assessment. In this work, we performed task and performance analysis of ESD surgeries. METHODS: We performed a detailed colorectal ESD task analysis and identified the critical ESD steps for lesion identification, marking, injection, circumferential cutting, dissection, intraprocedural complication management, and post-procedure examination. We constructed a hierarchical task tree that elaborates the order of tasks in these steps. Furthermore, we developed quantitative ESD performance metrics. We measured task times and scores of 16 ESD surgeries performed by four different endoscopic surgeons. RESULTS: The average time of the marking, injection, and circumferential cutting phases are 203.4 (σ: 205.46), 83.5 (σ: 49.92), 908.4 s. (σ: 584.53), respectively. Cutting the submucosal layer takes most of the time of overall ESD procedure time with an average of 1394.7 s (σ: 908.43). We also performed correlation analysis (Pearson's test) among the performance scores of the tasks. There is a moderate positive correlation (R = 0.528, p = 0.0355) between marking scores and total scores, a strong positive correlation (R = 0.7879, p = 0.0003) between circumferential cutting and submucosal dissection and total scores. Similarly, we noted a strong positive correlation (R = 0.7095, p = 0.0021) between circumferential cutting and submucosal dissection and marking scores. CONCLUSIONS: We elaborated ESD tasks and developed quantitative performance metrics used in analysis of actual surgery performance. These ESD metrics will be used in future validation studies of our VESS simulator