Abstract
Boiling histotripsy (BH) is a focused ultrasound technology that uses millisecond-long
pulses with shock fronts to induce mechanical tissue ablation. The pulsing scheme
and mechanisms of BH differ from those of cavitation cloud histotripsy, which was
previously developed for benign prostatic hyperplasia. The goal of the work described
here was to evaluate the feasibility of using BH to ablate fresh ex vivo human prostate tissue as a proof of principle for developing BH for prostate applications.
Fresh human prostate samples (N = 24) were obtained via rapid autopsy (<24 h after
death, institutional review board exempt). Samples were analyzed using shear wave
elastography to ensure that mechanical properties of autopsy tissue were clinically
representative. Samples were exposed to BH using 10- or 1-ms pulses with 1% duty cycle
under real-time B-mode and Doppler imaging. Volumetric lesions were created by sonicating
1–4 rectangular planes spaced 1 mm apart, containing a grid of foci spaced 1–2 mm
apart. Tissue then was evaluated grossly and histologically, and the lesion content
was analyzed using transmission electron microscopy and scanning electron microscopy.
Observed shear wave elastography characterization of ex vivo prostate tissue (37.9 ± 22.2 kPa) was within the typical range observed clinically.
During BH, hyperechoic regions were visualized at the focus on B-mode, and BH-induced
bubbles were also detected using power Doppler. As treatment progressed, hypoechoic
regions of tissue appeared, suggesting successful tissue fractionation. BH treatment
was twofold faster using shorter pulses (1 ms vs. 10 ms). Histological analysis revealed
lesions containing completely homogenized cell debris, consistent with histotripsy-induced
mechanical ablation. It was therefore determined that BH is feasible in fresh ex vivo human prostate tissue producing desired mechanical ablation. The study supports further
work aimed at translating BH technology as a clinical option for prostate ablation.
Key Words
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Article info
Publication history
Published online: October 04, 2022
Accepted:
July 31,
2022
Received in revised form:
July 27,
2022
Received:
April 2,
2022
Identification
Copyright
© 2022 World Federation for Ultrasound in Medicine & Biology. All rights reserved.
