Evaluation of ice ball size as a function of freezing intensity through computed tomography scans during cryoablation procedures.

BACKGROUND: Cryoablation is a specific minimally invasive thermal ablation technique that destroys tumor targets using low temperatures, freezing the pathological tissue and forming an "ice ball" around it. The aim of this study is to analyze how the reduction in freezing intensity during a cryoablation procedure affects the size of the ice ball. MATERIALS AND METHODS: The experimentation was conducted on room-temperature ultrasound gel, using the ICEfx™ cryoablation system with IceSphere™ needles in single and multiple configurations (double, triple, and quadruple). Each configuration was studied using a freezing intensity of 100%, 70%, 50%, and 20%, with a single 10-minute freezing cycle. CT scans of the gel cubes were performed at the end of each freezing cycle to measure the dimensions of the individual ice balls. RESULTS: Results show that the reduction in freezing intensity affects the size of the ice balls in a nonlinear but exponentially decreasing manner. Furthermore, the calculation of the decrement factors for each dimension, for every configuration and intensity level, highlighted that the width and depth of the ice ball are the most reduced dimensions, while the height values undergo minimal variation. CONCLUSION: This study provides the operator with a practical guide for customizing and optimizing in vivo cryoablation. This enables careful selection of the best configuration and freezing intensity to ensure the exclusion of adjacent sensitive anatomical structures that need to be preserved from freezing.