In-vivo transcostal histotripsy therapy without aberration correction

Abstract

In a previous in vitro investigation, it was shown that histotripsy therapy can generate precise lesions through rib obstacles without aberration correction as long as the focal pressure amplitude is modulated to exclusively allow the main focal beam to exceed the bubble cloud initiation threshold. This study investigates the therapeutic capabilities of transcostal histotripsy ablation and its thermal impact on overlying tissues in vivo without using aberration correction methods. Treatments were conducted in 8 pigs, with 4 lesions generated through transcostal windows with full ribcage obstruction and 4 lesions created through transabdominal windows without rib coverage. A 750 kHz focused transducer was used to sonicate the targets using 5 cycle pulses at a repetition frequency of 200 Hz. Estimated in situ peak negative pressures of 13-17 MPa were generated at the focus. Each treatment lasted approximately 40 minutes to allow temperature measurements to saturate. Temperatures on overlying tissues including ribs were measured with needle thermocouples. Lesions were created by mechanically scanning the transducer focus, yielding comparable ablation volumes of 3.6 ± 1.7 cm3 and 4.5 ± 2.0 cm3 in transcostal and transabdominal treatments, respectively. The average temperature increase on the ribs in all transcostal treatments was 3.9 ± 2.1 °C, while in transabdominal treatments an increase of 1.7 ± 1.3 °C was observed. The results suggest that histotripsy therapy can deliver effective and safe treatment through the ribcage without requiring aberration correction or rib sparing methods.