From: Proceedings 10th World Congress of Cryosurgery
Simulation of prostate cryoablation

November 1998
J Jankun, M Jankun, TJ Kelly, S Selman Medical College of Ohio, Toledo, Ohio 43699-0008
Cryoablation therapy is a method of minimally invasive cancer treatment through use of liquid nitrogen to freeze and consequently to destroy tumors. Liquid nitrogen cools the tumour by a set of probes (call "cryoprobes") with adjustable flow rates, cooling temperature and activation time. Though cryoablation has been used for some time, the behavior of the cryoprobe system has not been extensively studied. For example, in prostate cancer treatment, the settings of the cryoprobe to achieve a frozen area of appropriate size and shape were developed empirically. The Cryoablation Simulator (or "CryoSim") is an attempt to provide a modeling, training, and automation platform for cryoablation therapy. Provided with the physical characteristics of the surrounding tissue, three-dimensional ultrasound of the affected region, and the positions and settings of the cryoprobes, CryoSim. calculates the isotherm of the "killing" region of frozen temperatures. This isotherm is depicted visually with reference to the surrounding tissue. Within the simulator, the user may move the probes, change cryoprobe settings and adjust their viewpoint. The simulator uses a discrete differential equation solver to calculate the temperature at user-adjustable grid-points in simulated space. CryoSim was developed using C++ and the Direct3D graphical libraries for Windows 95 and Windows NT. Initial simulations show reasonable conformity to known results. Future work includes further verification tests and integration into a mechanically driven system using CryoSim optimized placements. (Supported by grant from Ohio Aerospace InstituteNASA, 1997)

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