Computerized Planning for Multiprobe Cryosurgery using a Force-field Analogy

TLDR

Cryosurgery destroys unwanted tissues by freezing, and for internal organs multiple probes are inserted to maximize injury within a target region while sparing surrounding tissue. This study develops a computerized planning tool that selects optimal cryoprobe locations using bioheat transfer simulations. The tool employs an iterative optimization based on a force‑field analogy, running a transient bioheat simulation each cycle and moving probes in response to temperature‑derived forces, and is applicable to all cooling techniques. Compared to traditional numerical optimization, the method requires far fewer simulations and was illustrated with 2‑D prostate cryosurgery cross‑section examples.

Abstract

Cryosurgery is the destruction of undesired biological tissues by freezing. For internal organs, multiple cryoprobes are inserted into the tissue with the goal of maximizing cryoinjury within a predefined target region, while minimizing cryoinjury to the surrounding tissues. The objective of this study is to develop a computerized planning tool to determine the best locations to insert the cryoprobes, based on bioheat transfer simulations. This tool is general and suitable for all available cooling techniques and hardware. The planning procedure employs a novel iterative optimization technique based on a force-field analogy. In each iteration, a single transient bioheat transfer simulation of the cryoprocedure is computed. At the end of the simulation, regions of tissue that would have undesired temperatures apply “forces” to the cryoprobes directly moving them to better locations. This method is more efficient than traditional numerical optimization techniques, because it requires significantly fewer bioheat transfer simulations for each iteration of planning. For demonstration purposes, 2D examples on cross sections typical of prostate cryosurgery are given.