Cryoprobe isotherms: a caveat and review

Area of Science:

• Urology
• Oncology
• Thermal Medicine

Background:

• Cryotherapy is a thermal therapy for small renal masses, especially in high-risk patients.
• Optimal application and critical temperatures for in vivo cell death remain undefined.
• Temperature monitoring during cryotherapy procedures is not standard practice.

Purpose of the Study:

• To evaluate the accuracy of temperature monitoring during cryotherapy for renal masses.
• To assess the utility of in vitro gel models for predicting in vivo temperatures.
• To establish recommendations for improving cryotherapy accuracy in clinical practice.

Main Methods:

• Utilized in vitro gel, ex vivo porcine kidney, and in vivo porcine kidney models.
• Employed two commercially available cryotherapy units for experimentation.
• Investigated tissue temperature variability and the heat sink effect in renal tissue.

Main Results:

• Tissue temperatures during cryotherapy were found to be highly variable across models.
• In vitro gel models provided reproducible isotherms but were inaccurate for in vivo temperature prediction.
• The heat sink effect of highly vascular renal tissue significantly impacted temperature distribution.

Conclusions:

• Current cryotherapy practices for renal masses may lack optimal temperature control.
• In vitro gel models are not suitable for planning in vivo cryotherapy due to vascularity.
• Recommendations include placing cryoprobes through and beyond the tumor and using multi-point temperature sensing.