Abstract No. 83 Using Gelfoam to sculpt cryoablation growth: a phantom study

Abstract

Hydrodissection is a commonly used method to prevent thermal injury to tissue adjacent to an ablation zone. Instilling thicker material has the potential to impact thermal changes to tissues. The purpose of this experiment is to explore the insulative properties of Gelfoam compared to air, water, and normal saline (NS) using a gelatin cryoablation model. Cryoablation simulations were performed by interposing air, normal saline, Gelfoam slurry, or water on gelatin phantoms and measuring surrounding temperatures. Homemade gelatin phantoms were constructed mimicking the density of average liver tissue of 1.07 g/mL. Interposing substances were placed within a 1 cm wide × 5 cm long × 6 cm deep well. Cryoablation was performed using a single 2.1 Ice Force probe. Visual changes of iceball growth were recorded. Temperature recording was performed using Galil thermocouples placed perpendicular to the ablation probe with sampling occurring in 10mm intervals starting from 5mm from the probe to a distance of 35 mm from the probe. Control and study data was obtained at same time Gelatin phantoms demonstrated cryoablation zones consistent with published manufacturer nomograms. Insulative ability was calculated from the difference between lowest recorded control and lowest recorded hydrodissected thermocouple temperatures . Normal saline performed the best yielding a temperature differential of 50°C, followed by Gelfoam (40°C), and then room air (21°C). A second phantom was used to evaluate water versus NS where water outperformed NS (25°C vs 10°C). Gelfoam maintains physical properties allowing for localized separation that cannot be achieved with saline or pneumo-dissection. Normal simulated tissue 1 cm from gelatin remained safe (average temperatures above the lethal limit of -20°C), and Gelfoam itself recorded lowest absolute temperatures and control-experimental difference from control temperatures comparable to saline. Room air and water performed poorly reaching lethal temperatures. This study suggests that Gelfoam can be used in cryoablation dissection when localized, fixed physical separation is necessary.