Factors Affecting Lethal Isotherms During Cryoablation Procedures

Abstract

Background:Creating appropriately-sized, lethal isotherms during cryoablation of renal tumors is critical in order to achieve sufficiently-sized zones of cell death. To ensure adequate cell death in target treatment locations, surgeons must carefully select the type, size, location, and number of probes to be used, as well as various probe operating parameters.Objective:The current study investigates the effects of probe type, operating pressure, and clinical method on the resulting sizes of isotherms in an in vitro gelatin model.Method:Using a total of four cryoprobes from two manufacturers, freeze procedures were conducted in gelatin in order to compare resulting sizes of constant temperature zones (isotherms). The effects of certain procedural parameters which are clinically adjustable were studied.Results:Test results show that the sizes of 0 °C,-20 °C and -40 °C isotherms created by similarly-sized probes from two different manufacturers were significantly different for nearly all comparisons made, and that size differences resulting from changing the operating pressure were not as prevalent. Furthermore, isotherm sizes created using a multiple freeze procedure (a ten minute freeze, followed by a five minute passive thaw, followed by another ten minute freeze) did not result in statistically-significant differences when compared to those created using a single freeze procedure in all cases.Conclusion:These results indicate that selection of the probe manufacturer and probe size may be more important for dictating the size of kill zones during cryoablation than procedural adjustments to operating pressures or freeze times.

Active surveillance and focal ablation for small renal masses: a better solution for comorbid patients

“…The shape and size of the ablation zone can be customized by activation or deactivation of some cryoprobes during the procedure, giving the interventional radiologist the ability to actively monitor the ablation zone via US, CT or MRI due to iceball formation [21]. Moreover, the extent of the ablation zone is dependent on cryoprobe manufacturer or cryoprobe size [22]. In the case of cryoablation, two approaches are performed: percutaneous (PCA) and open/laparoscopic surgical (SCA) [23,24].…”

Percutaneous CT‐Guided Cryovagotomy in Patients with Class I or Class II Obesity: A Pilot Trial

“…Third, the predicted in vivo ablation zone temperatures were not verified. As with all cryoablation technology to date, extrapolations must be made from benchtop isotherms to human procedures without real‐time knowledge of the effects of probe depth, tissue type, adjacent vessels, or time on the actual ablation zone temperatures .…”