Factors Affecting Tissue Cavitation during Burst Wave Lithotripsy

Area of Science:

• Biomedical Engineering
• Nephrology
• Medical Imaging

Background:

• Burst wave lithotripsy (BWL) is an investigational technology for non-invasive urinary stone fragmentation.
• Ultrasound parameters in BWL can induce cavitation, potentially causing renal injury.

Purpose of the Study:

• To measure the in vivo focal pressure amplitude threshold for cavitation in renal tissue.
• To assess the consistency of this threshold in native tissue, implanted stone models, and under varied exposure parameters.

Main Methods:

• Utilized transcutaneous BWL ultrasound pulses on pig kidneys.
• Employed an active cavitation imaging method (power Doppler ultrasound) to detect cavitation.
• Determined pressure thresholds by incrementally adjusting amplitude until cavitation onset/cessation.

Main Results:

• The presence of an implanted stone or sham surgery did not significantly alter the tissue cavitation threshold.
• Targeting the renal parenchyma, rather than the collecting space, increased the pressure threshold for cavitation.
• Lowering the ultrasound pulse repetition frequency also resulted in a higher pressure threshold for cavitation.

Conclusions:

• In vivo cavitation thresholds in renal tissue are influenced by BWL exposure parameters.
• Targeting parenchyma and reducing pulse repetition frequency may offer safer BWL parameters by increasing cavitation thresholds.