The cavitation threshold of human tissue exposed to 0.2-MHz pulsed ultrasound: Preliminary measurements based on a study of clinical lithotripsy

A. J. Coleman, T. Kodama, M. J. Choi, T. Adams, J. E. Saunders

Research output: Contribution to journalArticlepeer-review

61 Citations (Scopus)

Abstract

Evidence of acoustic cavitation was identified in the form of transient echoes in ultrasound B-scan images of patients receiving extracorporeal shock-wave lithotripsy treatment on a Storz Modulith SL20. This lithotripter generates 10-μs duration pulses with a centre frequency of 0.2 MHz at a pulse repetition frequency of 1 Hz. The visual appearance of B-scan images was examined in a total of 30 patients and a quantitative analysis of echogenicity changes was carried out in six cases involving lithotripsy treatment of stones in the renal pelvis. In these patients new echoes were identified in images unaffected by movement artefacts and were found to occur in perinephric fat and adjacent muscle and kidney tissue at positions close to the axis of the shock-wave field between 1 and 2 cm in advance of the indicated beam focus of the lithotripter. The echogenicity within each region increased significantly above the background level when the output of the lithotripter was increased above a threshold value. The acoustic pressures corresponding to this threshold were measured in water using a calibrated PVDF membrane hydrophone. After correction for attenuation in tissue the cavitation thresholds, in terms of the temporal peak negative pressure, are found to lie between 1.5 MPa and 3.5 MPa in all six cases. Interpretation of the measured values in terms of the likely threshold at the higher frequencies used in diagnostic ultrasound is considered using a theoretical model.

Original languageEnglish
Pages (from-to)405-417
Number of pages13
JournalUltrasound in Medicine and Biology
Volume21
Issue number3
DOIs
Publication statusPublished - 1995
Externally publishedYes

Keywords

  • Cavitation
  • Lithotripsy
  • Ultrasonics

ASJC Scopus subject areas

  • Biophysics
  • Radiological and Ultrasound Technology
  • Acoustics and Ultrasonics

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