Predicting and planning cryoablation procedures

We developed a planning tool that can accurately predict the size of the ice ball in multiple probe cryoablation procedures (4 mm average error). This tool accounts for perfusion differences in different types of tissue (kidney, liver, soft tissue, fat), as well as synergy between probes. The user specifies the desired size of the ablation zone, and the planning tool determines the optimal probe spacing and ablation time.

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Boas FE, Srimathveeravalli G, Kaye EA, Durack JC, Erinjeri JP, Ziv E, Maybody M, Yarmohammadi H, Solomon SB. (2017) "Development of a searchable database of cryoablation simulations for use in treatment planning." Cardiovascular and Interventional Radiology. In press.

Boas FE, Srimathveeravalli G, Kaye E, Durack JC, Erinjeri JP, Ziv E, Maybody M, Yarmohammadi H, Solomon SB. "Development of a searchable database of cryoablation simulations, for use in treatment planning." JVIR 27(3): S31. Oral presentation at SIR, Vancouver, 2016-04-03.

Abstract

Purpose: To create and validate a planning tool for multiple-probe cryoablation, using simulations of ice ball size and shape for various ablation probe configurations, ablation times, and types of tissue ablated.

Materials and methods: Ice ball size and shape was simulated using the Pennes bioheat equation. 5670 different cryoablation procedures were simulated, using 1-6 cryoablation probes and 1-2 cm spacing between probes. The resulting ice ball was measured along three perpendicular axes and recorded in a database. Simulated ice ball sizes were compared to gel experiments (26 measurements) and clinical cryoablation cases (42 measurements). The clinical cryoablation measurements were obtained from a HIPAA-compliant retrospective review of kidney and liver cryoablation procedures between January 2015 and February 2016. Finally, we created a web-based cryoablation planning tool, which uses the cryoablation simulation database to look up the probe spacing and ablation time that produces the desired ice ball shape and dimensions.

Results: Average absolute error between the simulated and experimentally measured ice balls was 1 mm in gel experiments, and 4 mm in clinical cryoablation cases. The simulations accurately predicted the degree of synergy in multiple-probe ablations. The cryoablation simulation database covers a wide range of ice ball sizes and shapes up to 9.8 cm.

Conclusion: Cryoablation simulations accurately predict the ice ball size in multiple-probe ablations. The cryoablation database can be used to plan ablation procedures: given the desired ice ball size and shape, it will find the number and type of probes, probe configuration and spacing, and ablation time required.


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