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Factors Affecting Lethal Isotherms During Cryoablation Procedures
Andrew C Rau1, Ryan Siskey1, Jorge A Ochoa2
1Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104, United States.
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.
Insights
Probe selection is key for effective renal cryoablation. Different cryoprobe manufacturers and sizes significantly impact lethal isotherm size, more so than pressure or freeze duration adjustments.
Area of Science:
- Medical Devices
- Oncology
- Surgical Technology
Background:
- Achieving adequate cell death in renal tumor cryoablation requires precise control over lethal isotherm size.
- Surgeons must optimize probe selection (type, size, location, number) and operating parameters for effective treatment.
- Understanding factors influencing isotherm dimensions is critical for successful cryoablation outcomes.
Purpose of the Study:
- To investigate how cryoprobe type, operating pressure, and clinical method influence isotherm sizes in an in vitro gelatin model.
- To compare the impact of different cryoprobe manufacturers on isotherm dimensions.
- To evaluate the effect of procedural variations on the resulting freeze zones.
Main Methods:
- Utilized four cryoprobes from two manufacturers in an in vitro gelatin model.
- Conducted freeze procedures to compare the sizes of constant temperature zones (isotherms).
- Studied the effects of clinically adjustable parameters like operating pressure and freeze protocols (single vs. multiple freeze cycles).
Main Results:
- Significant differences in isotherm sizes (0 °C, -20 °C, -40 °C) were observed between probes from different manufacturers, even when similarly sized.
- Variations in operating pressure showed less impact on isotherm size compared to probe manufacturer differences.
- Multiple freeze procedures did not consistently yield statistically significant differences in isotherm sizes compared to single freeze procedures.
Conclusions:
- Cryoprobe manufacturer and probe size are critical determinants of renal cryoablation kill zones.
- Procedural adjustments, such as operating pressure and freeze duration, appear less influential than initial probe selection.
- This highlights the importance of careful cryoprobe selection for optimizing therapeutic outcomes in renal tumor cryoablation.
