Abstract No. 489 Evaluation of microwave ablation zone temperature following administration of a novel thermal accelerant agent in swine: An MR thermometry study

Abstract

To evaluate the effects of a novel thermal accelerant (TA) agent on microwave ablation zone temperature using real-time magnetic resonance thermometry (MRT) in porcine liver and skeletal muscle. This study was performed following IACUC approval. Castrated adult male domestic swine underwent microwave ablation under general endotracheal anesthesia. The Surblate system (Vision Medical, Santa Clara, CA) was used for all ablation treatments at a generator power of 100W and a frequency of 2,450 MHz for 5 or 10 minutes. Treatments were performed percutaneously with and without injection of 2-3 mL TA via a 5 Fr catheter at a distance of approximately 1.5 cm from the ablation antenna within normal liver and skeletal muscle. Separately, ablations were also performed in ex vivo whole livers. Real-time MRT was conducted on a 3.0 Tesla scanner (Siemens, Erlangen, DE) using a multigradient echo sequence with fat suppression and respiratory gating. Frequency-derived thermal maps were generated according to the slope of the phase vs. TE line on a per-pixel basis with temperature change calculated from the known temperature dependence of the water proton chemical shift. Ablation zone temperature change was quantified according to the volume of tissue that achieved a cytotoxic temperature greater than or equal to 60°C (V60). Data were analyzed with SAS/GLIMMIX using generalized mixed modeling and sandwich estimation assuming a lognormal distribution. Statistical significance was set at α = 0.05. A total of 34 ablations were performed (in vivo liver: 8 TA, 8 control; ex vivo liver: 7 TA, 5 control; in vivo muscle: 3 TA, 3 control). Mean V60 was significantly higher among TA ablations in both the in vivo and ex vivo liver groups when compared with controls (27.6 cm3 vs. 18.6 cm3 and 63.1 cm3 vs. 43.7 cm3, respectively; p<0.01). A trend toward significance was observed in the TA muscle ablation group (42.0 cm3 vs. 28.8 cm3; p = 0.07). In all three experimental conditions, an approximately 50% increase in V60 was seen with TA use. The use of thermal accelerant results in higher ablation zone temperatures as assessed by MRT. Further investigations in animal and human subjects are planned.