title: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors: Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104, United States.
authors: Andrew C
authors: AC
authors: Rau
authors: Exponent, Inc., 3440 Market Street, Suite 600, Philadelphia, PA 19104, United States.
authors: Ryan
authors: R
authors: Siskey
authors: Exponent, Inc., Menlo Park, CA, United States.
authors: Jorge A
authors: JA
authors: Ochoa
authors: Product Development, Healthtronics, Inc., Austin, TX, United States.
authors: Tracy
authors: T
authors: Good
keywords: Cryoablation; In vitro gelatin model; Lethal Isotherms; Probes; renal tumors