Non-invasive comminution of renal calculi using pulsed cavitational ultrasound therapy - histotripsy

The current clinically available procedure for non-invasively treating renal calculi, extracorporeal shock wave lithotripsy (ESWL), suffers from the fact that it can result in incomplete fractionation of the stone and confer damage to both renal and extra-renal tissues. We assessed the feasibility of using histotripsy to non-invasively erode kidney stones to fine debris and performed a comparison study with a piezoelectric lithotripter. Eight Ultracal-30 model stones were treated for five minutes with each modality. The results show the following: (1) 100% of stone debris produced by histotripsy was less than 100 ¿m in diameter, while 32% of that produced by lithotripsy exceeded 2 mm. (2) Histotripsy achieved a stone erosion rate of 26 mg/min; the fragmentation rate with lithotripsy was 111 mg/min. (3) Treatment of stones embedded in a tissue-phantom for visualizing cavitation damage indicated that minimal collateral damage is produced by each modality. (4) Acoustic backscatter measurements suggest that loss of stone mass is highly correlated with the extent of bubble cloud activity with histotripsy.