A PVDF Receiver for Ultrasound Monitoring of Transcranial Focused Ultrasound Therapy

Department of Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON M4N3M5, Canada.
IEEE transactions on bio-medical engineering (Impact Factor: 2.35). 09/2010; 57(9):2286-94. DOI: 10.1109/TBME.2010.2050483
Source: PubMed


Focused ultrasound (FUS) shows great promise for use in the area of transcranial therapy. Currently dependent on MRI for monitoring, transcranial FUS would benefit from a real-time technique to monitor acoustic emissions during therapy. A polyvinylidene fluoride receiver with an active area of 17.8 mm (2) and a film thickness of 110 mum was constructed. A compact preamplifier was designed to fit within the receiver to improve the receiver SNR and allow the long transmission line needed to remove the receiver electronics outside of the MRI room. The receiver was compared with a 0.5 mm commercial needle hydrophone and focused and unfocused piezoceramics. The receiver was found to have a higher sensitivity than the needle hydrophone, a more wideband response than the piezoceramic, and sufficient threshold for detection of microbubble emissions. Sonication of microbubbles directly and through a fragment of human skull demonstrated the ability of the receiver to detect harmonic bubble emissions, and showed potential for use in a larger scale array. Monitoring of disruption of the blood-brain barrier in rats showed functionality in vivo and the ability to detect subharmonic, harmonic, and wideband emissions during therapy. The receiver shows potential for monitoring acoustic emissions during treatments and providing additional parameters to assist treatment planning. Future work will focus on developing a multi-element array for transcranial treatment monitoring.

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    • "However, the nonlinear nature of bubble oscillations allows using the subharmonic to detect stable cavitation experimentally (Neppiras 1968, Mestas et al 2003, Vykhodtseva et al 1995, McLaughlan et al 2010). Subharmonic emissions from cavitation are well established theoretically (Eller and Flynn 1969, Prosperetti 1974, Katiyar and Sarkar 2011), and are known to correlate experimentally with several in vivo and in vitro bioeffects, such as ultrasound-enhanced thrombolysis (Prokop et al 2007), disruption of the blood brain barrier (O'Reilly and Hynynen 2010), chemotherapy drug release from micelles (Husseini et al 2005), and enhanced heating in focused ultrasound surgery (Sokka et al 2003). Thus knowledge of the threshold of subharmonic emissions could be used to gauge the potential for clinically beneficial bioeffects. "
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