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Computerized Planning of Prostate Cryosurgery with Pullback Operation Prostate cryosurgery is frequently performed as a two-stage procedure, in which the first stage targets freezing at a greater insertion depth of cryoprobes, while the second stage of freezing is performed after some cryoprobes are pulled back to new locations (also known as the “pullback procedure”). The purpose of this web page is to demonstrate a proof-of-concept for automated pullback planning, using the so-called bubble-packing technique. This demonstration is performed on Prostate Model D. The simulated cryoprobes have characteristics typical to Joule-Thomson-based cryoprobes with Argon as a working gas, where the cryoprobe diameter is 1.5 mm and its active length is 15 mm. Results are verified with 3D bioheat simulations, and final surface temperature of the prostate is presented in each movie below. In total, four cases are demonstrated here, all having 14 cryoprobes in stage I, while the number of active cryoprobes in stage II varies in the range of 4 to 14. For demonstration purposes only, the insertion depth in each stage is kept uniform, where automated variable insertion depth in each stage is a work in progress. The planning isotherm in this demonstration is -22°C, which splits the temperature range between the onset of tissue freezing (~0°C) and the lethal temperature (~-45°C), as illustrated above. However, the actual value of the planning isotherm is left for the selection of the clinician. The quality of planning is evaluated using the defect region concept, where a defect is defined as either an internal area to the target region possessing temperatures above the planning isotherm, or external area to the target region possessing temperatures below the planning isotherm. Overall defect areas from the four cases presented below are in the range of 25% to 27% of the target region volume.
Stage I: 14 Cryoprobe Stage II: 4 Cryoprobes	Stage I: 14 Cryoprobes Stage II: 7 Cryoprobes	Stage I: 14 Cryoprobes Stage II: 11 Cryoprobes	Stage I: 14 Cryoprobes Stage II: 14 Cryoprobes
This research has been supported, in part, by the National Institute of Biomedical Imaging and Bioengineering (NIBIB) NIH Grant # 1R01EB003563
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