Histotripsy Group
    Biomedical Engineering Department, University of Michigan

Research -> Histotripsy Chronic Bioeffects

Histotripsy Chronic Bioeffects


Long-term effects and the evolution of histologic changes in histotripsy generated disrupted tissue remain poorly understood. This study aimed to characterize the 0-60 day histology of cavitational ablation in a rabbit model [12]. 29 New Zealand White rabbits were anesthetized and exposed to high intensity pulses of ultrasound (60000 pulses, 20 usec duration, 750 kHz, 1 kHz PRF, 18 MPa peak rarefactional pressure, lower pole, left kidney). Kidneys were harvested immediately from five rabbits. The others were recovered and the kidneys were harvested 1, 2, 7, 20, or 60 days after treatment. Grossly, kidneys from 0-2 days displayed subcapsular bruising near the exposure site and some hemorrhage in the adjacent perirenal fat; microscopically, a disrupted, acellular zone measuring 3-5 mm by 5-10 mm accompanied by local infiltration of neutrophils (acute inflammation) was seen. Kidneys harvested after 7 days displayed tubular dilatation adjacent to the targeted area and collagen deposition consistent with scar formation. Decreased collagen deposition, decreased size of the disrupted zone, and regeneration of the tubular basal cell layer of dilated tubules was evident by day 20. Kidneys harvested at 20 and 60 days had contour defects near the exposure site with an apparent volume loss. Cavitation causes orderly and predictable histologic changes. Local renal damage induced during histotripsy may be partially reversible. Further research is needed to identify the clinical correlates of the observed histologic findings.

References:
Hall TL, Kieran K, Fowlkes JB, Cain CA, Roberts WW, "Temporal trends in the histology of the rabbit kidney after cavitational tissue ablation," 6th International Symposium on Therapeutic Ultrasound, S07 (2006).