Guidelines for power and time variables for microwave ablation in an in vivo porcine kidney.
OBJECTIVE
Microwave technology provides an emerging thermal ablation technique for solid organ tumors. We propose guidelines and recommend optimal time and power for use.


METHODS
Microwave ablations using a VivaWave Microwave Ablation System (Valleylab, Boulder, CO) were performed in vivo in a porcine kidney model. The independent variables were power (20, 30, 40, 45, 50, 60 W) and time (2, 4, 6, 8, 10, 15, 20 min) with the outcome variable diameter of ablation. Following ablations, kidneys were procured for gross and histological evaluation. Analysis of variance (ANOVA) was used followed by Tukey tests when appropriate. A P value of <0.05 was considered statistically significant.


RESULTS
In 308 total ablations, a minimum of 7 ablations were performed in 35 of 42 power and time variables (83%). The outcome variable, ablation diameter, was affected significantly by time, power, and time/power interaction (P < 0.0001). For each time point, a one-way ANOVA showed an overall significant difference in ablation size X wattage (P < 0.0001). Tukey tests showed that, at each time point, ablation sizes at 45, 50, and 60 W were not significantly different. After determining that 45 W was optimal, a one-way ANOVA showed an overall significant difference in ablation sizes for time points at 45 W (P < 0.0001). Tukey tests showed that, at 45 W, ablation sizes at 10 min were significantly larger than ablation sizes at 8, 6, 4, and 2 min.


CONCLUSIONS
We propose guidelines for use of a novel microwave ablation system and recommend use at 45 W for 10 min.
Hope
William W
WW
Division of Gastrointestinal and Minimally Invasive Surgery, Carolinas Medical Center, Charlotte, North Carolina 28203, USA.
Schmelzer
Thomas M
TM
Newcomb
William L
WL
Heath
Jessica J
JJ
Lincourt
Amy E
AE
Norton
H James
HJ
Heniford
B Todd
BT
Iannitti
David A
DA
D055011:Ablation Techniques; D000818:Animals; D002292:Carcinoma, Renal Cell / Q000601:surgery; D005260:Female; D007668:Kidney / Q000601:surgery*; D007680:Kidney Neoplasms / Q000601:surgery; D008872:Microwaves / Q000627:therapeutic use*; D013552:Swine