Investigation of High Pulse Repetition Frequency Single-Cycle Histotripsy for Rapid Tissue Ablation.

OBJECTIVE: Single-cycle histotripsy was investigated for the rapid ablation of porcine liver using high pulse repetition frequency (PRF) pulsing methods. Recent evidence from our group has suggested that single-cycle histotripsy does not experience a decrease in ablation efficiency across a wide range of PRFs. METHODS: Histotripsy ablation efficiency was quantified in a 1% agarose gel phantom containing a layer of red blood cells using a 500 kHz transducer with an F# of 0.61. Lesions were generated using PRFs of 500-2500 Hz at peak negative pressures of 15, 24 and 42 MPa with an 800 pulse exposure, with results compared to a low PRF control (1 Hz). Second, high PRFs were used for volumetric ablations of porcine liver using doses of 400-800 pulses per point. Tissue damage was assessed via ultrasound imaging and histologically using Masson's trichrome staining. RESULTS: Ablation experiments in red blood cell gel phantoms showed no significant differences in ablation efficacy as PRF increased from 500 to 2500 Hz, supporting the hypothesis that single-cycle histotripsy can achieve efficient tissue ablation at high PRFs. Volumetric tissue ablation experiments showed that single-cycle histotripsy resulted in effective tissue ablation for all tested PRFs, with near complete or complete ablation observed after 600-800 applied pulses. Partial ablation in some samples at lower doses (400 pulses for 500-1500 Hz PRF, 600 pulses for 2000-2500 Hz PRF and 800 pulses for 2500 Hz PRF) suggested a slight decrease in ablation effectiveness with increasing PRF. CONCLUSION: This study supports the hypothesis that high PRF single-cycle histotripsy can achieve faster tissue ablation while maintaining precise volumetric lesion generation.