03:09 PM Abstract No. 279 Robotically assisted sonic therapy (RAST) for noninvasive subcutaneous fat ablation in a porcine model

Abstract

Robotically assisted sonic therapy (RAST) is an ablation modality based on histotripsy, a non-invasive, non-thermal method of focused ultrasound tissue destruction. The purpose of this study was to evaluate the acute and chronic effects of RAST subcutaneous fat ablation in a live porcine model. Five female swine underwent 10 RAST subcutaneous (SQ) fat ablations. The ablations were divided into three groups: acute (n=4, immediate sacrifice), subacute (n=2, sacrifice day 7), and chronic (n=4, sacrifice day 28). RAST was performed with a custom therapy transducer (VortxRx, Histosonics, Inc.) with a prescribed 4.0 x 4.0 x 2.0 cm ovoid ablation zone (prescribed volume=16.8 cm3) targeted to the SQ posterior thoracic fat. Post procedural MRI’s were obtained on Days 7 (n=5) and 28 (n=4) and ablations reviewed for size and appearance. Skin firmness and indentation was rated on a scale of 1-3 during physical examination at day 0, day 7 and day 28 (Firmness Score 1 = no firmness, 2 = mild firmness, 3 = hard; Indentation Score: 1 = no indentation, 2 = mild indentation, 3 = deep indentation). Ablation zones were removed at necropsy and processed for pathologic analysis. All procedures were well-tolerated, with a technical success rate of 9/10. Mean treatment time was 35.5 min. One ablation on a subacute animal was aborted after inadequate anesthesia and intraprocedural movement. At one-week post procedure ablations had a mean volume of 15.7 cm3 (SD ±0.77), and measured 3.9 (0.8), 3.6 (0.1) and 1.9 (0.1) in CC, transverse, and AP dimensions. At four-weeks, volume was 12.9 (SD ±1.3) cm3 (18% decrease) and corresponding lesion measurements were 3.6 (0.1), 3.3 (0.2), and 2.2 (0.1) in CC, transverse, and AP dimensions. The mean Firmness and Indentation scores at physical examination were 0 and 0 at day 0, 7, and 28 with no evidence of injury to the overlying skin. RAST is able to safely and precisely ablate SQ fat in this porcine model. Further work appears warranted, including ablation of mesenteric fat to explore the use of RAST as both a cosmetic and metabolic intervention.