Image not available

Duryea AP et al, 2015: Removal of residual cavitation nuclei to enhance histotripsy erosion of model urinary stones.

Duryea AP, Roberts WW, Cain CA, Hall TL

Abstract

Histotripsy has been shown to be an effective treatment for model kidney stones, eroding their surface to tiny particulate debris via a cavitational bubble cloud. However, similar to shock wave lithotripsy, histotripsy stone treatments display a rate-dependent efficacy, with pulses applied at a low rate generating more efficient stone erosion in comparison with those applied at a high rate. This is hypothesized to be the result of residual cavitation bubble nuclei generated by bubble cloud collapse. Although the histotripsy bubble cloud only lasts on the order of 100 μs, these microscopic remnant bubbles can persist on the order of 1 s, inducing direct attenuation of subsequent histotripsy pulses and influencing bubble cloud dynamics. In an effort to mitigate these effects, we have developed a novel strategy to actively remove residual cavitation nuclei from the field using low-amplitude ultrasound pulses. Previous work has demonstrated that with selection of the appropriate acoustic parameters these bubble removal pulses can stimulate the aggregation and subsequent coalescence of microscopic bubble nuclei, effectively deleting them from the target volume. Here, we incorporate bubble removal pulses in histotripsy treatment of model kidney stones. It was found that when histotripsy is applied at low rate (1 Hz), bubble removal does not produce a statistically significant change in erosion. At higher pulse rates of 10, 100, and 500 Hz, incorporating bubble removal results in 3.7-, 7.5-, and 2.7-fold increases in stone erosion, respectively. High-speed imaging indicates that the introduction of bubble removal pulses allows bubble cloud dynamics resulting from high pulse rates to more closely approximate those generated at the low rate of 1 Hz. These results corroborate previous work in the field of shock wave lithotripsy regarding the ill effects of residual bubble nuclei, and suggest that high treatment efficiency can be recovered at high pulse rates through appropriate manipulation of the cavitation environment surrounding the stone.

IEEE Trans Ultrason Ferroelectr Freq Control. 2015May;62(5):896-904. doi: 10.1109/TUFFC.2015.7001. 

Rate this blog entry:
1
 

Comments 1

Othmar Wess on Monday, 28 September 2015 07:39

This is another paper of Duryea and co-workers being about cavitation nuclei and their impact on kidney stone treatment by histotripsy. All in vitro experiments circle around increasing histotripsy efficiency which may be a valuable adjunct to SWL. The rationale of using histotripsy instead of or in addition to SWL is the idea to erode larger fragments to smaller sand like particles for ease of passing through natural channels. This would be most desirable since larger residual fragments are often left after SWL. As in previous papers ultrasonic bubble removal pulses intermittently applied reduce residual cavitation nuclei and thus enhance efficacy of histotripsy. However, although the applied acoustic power is quite high (P- 45MPa which is in the range of P+ of shock waves used in lithotripsy), the erosion rate is only 21mg/min with bubble removal pulses compared to 2.8 mg/min without bubble removal pulses.
Nevertheless, this is an interesting approach to improve SWL results. Several significant practical hurdles need to be overcome before it may be effective in clinical use. Some critical questions require further studies: What are the erosions results in vivo? Can this type of energy be applied without lesions of the tissue passed by the waves? Would the radiation pressure dislocate small particles out of the treatment zone before erosion?
We are looking forward to hear about progress.

This is another paper of Duryea and co-workers being about cavitation nuclei and their impact on kidney stone treatment by histotripsy. All in vitro experiments circle around increasing histotripsy efficiency which may be a valuable adjunct to SWL. The rationale of using histotripsy instead of or in addition to SWL is the idea to erode larger fragments to smaller sand like particles for ease of passing through natural channels. This would be most desirable since larger residual fragments are often left after SWL. As in previous papers ultrasonic bubble removal pulses intermittently applied reduce residual cavitation nuclei and thus enhance efficacy of histotripsy. However, although the applied acoustic power is quite high (P- 45MPa which is in the range of P+ of shock waves used in lithotripsy), the erosion rate is only 21mg/min with bubble removal pulses compared to 2.8 mg/min without bubble removal pulses. Nevertheless, this is an interesting approach to improve SWL results. Several significant practical hurdles need to be overcome before it may be effective in clinical use. Some critical questions require further studies: What are the erosions results in vivo? Can this type of energy be applied without lesions of the tissue passed by the waves? Would the radiation pressure dislocate small particles out of the treatment zone before erosion? We are looking forward to hear about progress.
Guest
Thursday, 17 August 2017
STORZ MEDICAL AG
Lohstampfestrasse 8
8274 Tägerwilen
Switzerland
Tel.: +41 (0)71 677 45 45
Fax: +41 (0)71 677 45 05

www.storzmedical.com
Personal data
Address
Contact data
Message