RESEARCH ARTICLE


Factors Affecting Lethal Isotherms During Cryoablation Procedures



Andrew C. Rau1, *, Ryan Siskey1, Jorge A. Ochoa2, Tracy Good3
1 Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104, United States
2 Exponent, Inc., Menlo Park, CA, United States
3 Product Development, Healthtronics, Inc., Austin, TX, United States


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Creative Commons License
© Rau et al. Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104, USA; E-mail:arau@exponent.com


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.

Keywords: Cryoablation, In vitro gelatin model, Lethal Isotherms, Probes, renal tumors.