104 Super Critical Nitrogen: Assessing the performance and thermal characteristics of a novel cryosurgical device

Abstract

Today’s cryosurgical devices can be characterized by the type of cryogen employed. The most common, and current industry standard, utilizes a gas undergoing Joule-Thomson (JT) cooling. These gaseous cryogen devices can use small diameter probes that generate freezing temperatures near instantaneous, but due to the sub-optimal heat extraction of gases, often require large numbers of probes and/or extended applications. In contrast, liquid cryogen devices offer superior heat extraction, but with larger and slower acting probes. We recently developed a novel platform utilizing super critical nitrogen (SCN) as the cryogen, and have set out to quantify the performance of the system and compare it to that of an argon JT device. In this study, the isotherms generated during a freeze procedure were assessed with thermocouple arrays in various tissue approximations: water, ultrasound gel, and porcine muscle sections. It was found that the SCN system created significantly colder nadir temperatures (−170 °C as compared to −140 °C) and did so in approximately half the time. Additionally, the SCN system generated −40 °C and −20 °C isotherm volumes that were 300% and 32% larger than those of a JT device. Finally, comparing the surface freezing of porcine muscle sections (5–10 mm thickness), it was found that the SCN platform created full thickness lesions that were colder and more defined than JT devices while requiring less than half the freeze duration. The use of the SCN platform combines the miniaturization and speed of a JT device with the ultra cold nadir temperatures and cooling potential of a liquid nitrogen system and may represent the next generation of cryosurgical devices. Source of funding: CPSI Biotech. Conflict of interest: None declared. arobilotto@cpsibiotech.com