Histotripsy Group
    Biomedical Engineering Department, University of Michigan

High Speed Imaging

Acoustic Monitoring

Optical Monitoring

Histotripsy Mechanism -> Optical Monitoring

Optical Monitoring

An optical method was used to monitor the intensity loss of transmitted light through bubbles. The bubble cloud collapse cycle and bubble dissolution time were studied. The collapse cycle of the bubble cloud generated by an ultrasound pulse of several μsec was ~40-300μs. The dissolution time of the residual bubbles was tens of mesc. Further, dynamics of the ultrasound generated bubble cloud highly depend on acoustic parameters. The collapse cycle of the bubble cloud was greater with longer pulses, higher pulse pressure, higher pulse repetition frequency and higher gas concentration. These results provide rational explanations on the effects of acoustic parameters on erosion.

Example of a transmitted light through the bubble cloud detected by a photo-detector. The bubble cloud was generated by an 8-μs histotripsy pulse. The top left arrow indicates the arrival of the histotripsy pulse. The light intensity started to decrease at the arrival of the histotripsy pulse and last for 187 μs before its collapse. The insert is an expanded view of the optical signal during the hisotripsy pulse. The optical signal tracked the ultrasound waveform during the pulse, most likely due to the water index of refraction change caused by the ultrasound pressure fluctuation.

Xu Z, TL Hall, JB Fowlkes, and CA Cain. Optical and acoustic monitoring of bubble cloud dynamics at a tissue-fluid interface in ultrasound tissue erosion. J Acoust Soc Am 2007; vol. 121: 2421-2430.