[CRYOSURGERY IN ONCOLOGY].

Cryodestruction remains one of the effective methods of treatment. There is collected the sufficient experience of its application in oncology and described the positive changes in the immune status of patients after cryodestruction. The technology of minimally invasive percutaneous puncture cryotherapy expands treatment options but requires training and implementing new equipment of domestic production into practice.

Computerized training of cryosurgery - a system approach.

The objective of the current study is to provide the foundation for a computerized training platform for cryosurgery. Consistent with clinical practice, the training process targets the correlation of the frozen region contour with the target region shape, using medical imaging and accepted criteria for clinical success. The current study focuses on system design considerations, including a bioheat transfer model, simulation techniques, optimal cryoprobe layout strategy, and a simulation core framework. Two fundamentally different approaches were considered for the development of a cryosurgery simulator, based on a finite-elements (FE) commercial code (ANSYS) and a proprietary finite-difference (FD) code. Results of this study demonstrate that the FE simulator is superior in terms of geometric modeling, while the FD simulator is superior in terms of runtime. Benchmarking results further indicate that the FD simulator is superior in terms of usage of memory resources, pre-processing, parallel processing, and post-processing. It is envisioned that future integration of a human-interface module and clinical data into the proposed computer framework will make computerized training of cryosurgery a practical reality.

The role of exposure time in computerized training of prostate cryosurgery: performance comparison of surgical residents with engineering students.

PURPOSE: This study aims at the evaluation of a prototype of a computerized trainer for cryosurgery-the controlled destruction of cancer tumors by freezing. The hypothesis in this study is that computer-based cryosurgery training for an optimal cryoprobe layout is essentially a matter of exposure time, rather than trainee background or the specific computer-generated planning target. Key geometric features under considerations are associated with spatial limitations on cryoprobes placement and the match between the resulted thermal field and the unique anatomy of the prostate. METHODS: All experiments in this study were performed on the cryosurgery trainer-a prototype platform for computerized cryosurgery training, which has been presented previously. Among its key features, the cryosurgery trainer displays the prostate shape and its contours and provides a distance measurement tool on demand, in order to address spatial constraints during ultrasound imaging guidance. Another unique feature of the cryosurgery trainer is an output movie, displaying the simulated thermal field at the end of the cryoprocedure. RESULTS: The current study was performed on graduate engineering students having no formal background in medicine, and the results were benchmarked against data obtained on surgical residents having no experience with cryosurgery. Despite fundamental differences in background and experience, neither group displayed superior performance when it comes to cryoprobe layout planning. CONCLUSIONS: This study demonstrates that computer-based training of an optimal cryoprobe layout is feasible. This study demonstrates that the training quality is essentially related to the training exposure time, rather than to a specific planning strategy from those investigated.

A minimally invasive breast biopsy clinic: an innovative way to teach breast fellows how to perform breast ultrasound and ultrasound-guided breast procedures.

BACKGROUND: The ability to perform breast ultrasound and ultrasound-guided breast procedures are increasingly important skills for breast surgeons. Breast fellowship programs must develop programs to ensure adequate ultrasound training for breast fellows. METHODS: A Minimally Invasive Breast Biopsy Clinic was established at the Los Angeles County + University of Southern California Medical Center to provide breast fellows with comprehensive, hands-on, "live-patient" breast ultrasound training. RESULTS: From December 2004 though February 2005, 5 breast fellows received training in the Minimally Invasive Breast Biopsy Clinic. Each fellow received a minimum of 18 weeks of "live-patient" experience. Although the learning curve varied among the fellows, all showed proficiency in performing breast ultrasound and ultrasound-guided core biopsies by the 12th week. A total of 39 patients with fibroadenomas underwent 62 ultrasound-guided procedures, including 30 vacuum-assisted percutaneous excisions, 16 cryoablations, and 16 core biopsies. CONCLUSION: The Minimally Invasive Breast Clinic model provided breast fellows with sufficient "live-patient" experience to enable confident performance of breast ultrasound and ultrasound-guided breast procedures. The selection of patients with fibroadenomas facilitated safe and efficient training without interfering with the management of cancer patients.

Simulation-Based Cryosurgery Training: Variable Insertion Depth Planning in Prostate Cryosurgery.

A proof-of-concept for an advanced-level computerized training tool for cryosurgery is demonstrated, based on three-dimensional cryosurgery simulations and a variable insertion depth strategy for cryoprobes. The objective for system development is two-fold: to identify a cryoprobe layout in order to best match a planning isotherm with the target region shape and to verify that cryoprobe placement does not violate accepted geometric constraints. System validation has been performed by collecting training data from 17 surgical residents having no prior experience or advanced knowledge of cryosurgery. This advanced-level study includes an improved training session design in order to enhance knowledge dissemination and elevate participant motivation to excel. In terms of match between a planning isotherm and the target region shape, results of this demonstrate trainee performance improvement from 4.4% in a pretest to 44.4% in a posttest over a course of 50 minutes of training. In terms of combined performance, including the above-mentioned geometrical match and constraints on cryoprobe placement, this study demonstrates trainee performance improvement from 2.2% in the pretest to 31.1% in the posttest. Given the relatively short training session and the lack of prior knowledge, these improvements are significant and encouraging. These results are of particular significance, as they have been obtained from a surgical resident population which are exposed to the typical stress and constraints in advanced surgical education.

Graphics Processing Unit-Based Bioheat Simulation to Facilitate Rapid Decision Making Associated with Cryosurgery Training.

This study focuses on the implementation of an efficient numerical technique for cryosurgery simulations on a graphics processing unit as an alternative means to accelerate runtime. This study is part of an ongoing effort to develop computerized training tools for cryosurgery, with prostate cryosurgery as a developmental model. The ability to perform rapid simulations of various test cases is critical to facilitate sound decision making associated with medical training. Consistent with clinical practice, the training tool aims at correlating the frozen region contour and the corresponding temperature field with the target region shape. The current study focuses on the feasibility of graphics processing unit-based computation using C++ accelerated massive parallelism, as one possible implementation. Benchmark results on a variety of computation platforms display between 3-fold acceleration (laptop) and 13-fold acceleration (gaming computer) of cryosurgery simulation, in comparison with the more common implementation on a multicore central processing unit. While the general concept of graphics processing unit-based simulations is not new, its application to phase-change problems, combined with the unique requirements for cryosurgery optimization, represents the core contribution of the current study.

Simulation-Based Cryosurgery Intelligent Tutoring System Prototype.

As a part of an ongoing effort to develop computerized training tools for cryosurgery, the current study presents a proof of concept for a computerized tool for cryosurgery tutoring. The tutoring system lists geometrical constraints of cryoprobes placement, simulates cryoprobe insertion, displays a rendered shape of the prostate, enables distance measurements, simulates the corresponding thermal history, and evaluates the mismatch between the target region shape and a preselected planning isotherm. The quality of trainee planning is measured in comparison with a computer-generated planning, created for each case study by previously developed planning algorithms. The following two versions of the tutoring system have been tested in the current study: (1) an unguided version, where the trainee can practice cases in unstructured sessions and (2) an intelligent tutoring system, which forces the trainee to follow specific steps, believed by the authors to potentially shorten the learning curve. Although the tutoring level in this study aims only at geometrical constraints on cryoprobe placement and the resulting thermal histories, it creates a unique opportunity to gain insight into the process outside the operation room. Post-test results indicate that the intelligent tutoring system may be more beneficial than the nonintelligent tutoring system, but the proof of concept is demonstrated with either system.