Developing computerized tools for cryosurgery planning

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DESCRIPTION (provided by applicant): Cryosurgery has been known as an invasive surgical technique since 1961, when Cooper and Lee invented the first cryoprobe. In the 1990s, new developments in Joule-Thomson cooling (the cooling effect associated with a sudden relief of a pressurized gas) led to a dramatic decrease in the size of cryoprobes and an increase in the number of cryoprobes that could be used simultaneously. A dozen or more cryoprobes operating simultaneously in a single prostate cryosurgery is already common practice. If localized effectively, one of the primary benefits of using a large number of miniaturized cryoprobes is superior control over the freezing process. Currently, the process of selecting the correct placement of the cryoprobes for a specific procedure is an art held by the cryosurgeon, based on the surgeon's own experience and rules of thumb. Cryoprobes are typically operated in a trial-and-error fashion, until the entire target volume is thought to be frozen. Currently, there are no means to determine the optimal locations for the cryoprobes. Suboptimal cryoprobe localization may leave regions in the target volume unfrozen, may lead to cryoinjury of healthy surrounding tissues, may require an unnecessarily large number of cryoprobes, may increase the duration of the surgical procedure, and may increase the likelihood of post cryosurgery complications, all of which affect the quality and cost of the medical treatment. Computerized planning tools would help to alleviate these difficulties. The "cryoheater," a new device for cryosurgery control has recently been presented by the research team. The cryoheater is a temperature controlled electrical heater. In broad terms, cryoheaters can dramatically increase the ability to control the shape and size of the frozen region, however, to achieve the full benefits of cryoheaters, computerized planning tools for cryoheater localization are necessary. Our goal is to develop computerized planning tools for cryosurgery that are suitable for all available cooling techniques. The proposed research includes: (1) Development of an efficient numerical scheme for bioheat transfer simulations of cyroprocedures, (2) Development of an efficient optimization technique based on a force-field analogy. (3) Development of knowledge-based optimization techniques. (4) Experimental verification of the planning tool. Besides planning, another important application of the proposed tool is the training of cryosurgeons. The proposed tool will provide cryosurgeons with the ability to visualize the 3D volumetric nature of the freezing process. Likewise, it will allow the surgeon to explore the performance of various configurations of cryoprobes and cryoheaters, and observe the defects that would result from each. Such visualization capabilities will provide surgeons with insights into the physics of cryosurgery that are difficult to obtain from physical experiments or surgical practice.