Electronic Journal Technical Acoustics ISSN 1819-2408

Thanh C. Nguyen, Loan T. Bui, Nghia H. Tran, Victor Frenkel

Calibrating therapeutic ultrasound transducers: corrections for the effects of acoustic cavitation and acoustic streaming

language: English

received 01.01.2013, published 19.06.2013

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ABSTRACT

Commercial ultrasound power meters based on the radiation force technique are ubiquitously used in both the clinic and in laboratory settings for calibrating therapeutic ultrasound transducers. Despite their popularity, these devices are inherently inaccurate in that they do not compensate for the effects of acoustic cavitation and acoustic streaming. These factors can alter the displacement generated on the meter’s target, and hence the power being sensed. In the present study we built a low cost power meter comprised of a non-reflecting target suspended from an analytical balance in a water tank. Investigations in to the effects of cavitation and streaming were performed, where the former was shown to significantly lower the measured power and the latter was shown to increase it. Both effects were found to be proportional to the applied power as predicted by theory. A modified device was then constructed, where an acoustic permeable membrane was positioned directly over the target and shown to effectively eliminate the streaming effect. For the effects of cavitation, a pair of ultrasound transmitting and receiving transducers was positioned across the beam path, and custom software automatically calculated the attenuation coefficient of the water in the beam column. This was then used to correct for the attenuating effect of cavitation on the power being measured. In addition to correcting for sources of error associated with commercial devices, the setup can easily be constructed for a much lower cost using existing, off-the-shelve components found typically in the laboratory environment. The system may also be employed for research on the effects of water borne phenomena associated with the application of ultrasound in a fluid medium.

Key words: therapeutic ultrasound; calibration; radiation force balance; acoustic cavitation; attenuation; acoustic streaming.

15 pages, 7 figures

Сitation: Thanh C Nguyen, Loan T Bui, Nghia H Tran, Victor Frenkel. Calibrating therapeutic ultrasound transducers: corrections for the effects of acoustic cavitation and acoustic streaming. Electronic Journal “Technical Acoustics”, http://www.ejta.org, 2013, 5.

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		Thanh C. Nguyen received his Bachelors Degree in Electrical Engineering (EE) in 2013 from the Catholic University of America (CUA) in Washington, DC. He is presently working at the Center for Planning and Information Technology at CUA, and has applied to do his Masters degree at the University in EE, focusing on Network Security. е-mail: 32nguyen(at)cardinalmail.cua.edu
		Loan T. Bui received her Bachelors degree in Biomedical Engineering (BE) in 2012 at the Catholic University of America (CUA) in Washington, DC. She is currently pursuing a PhD in BE, and working as a research assistant at the University of Texas at Arlington. е-mail: lbui(at)mavs.uta.edu
		Nghia H. Tran received both his Bachelors and Masters degrees in 2012 in Electrical Engineering (EE) at the Catholic University of America (CUA) in Washington, DC. He is presently pursuing his PhD in EE at CUA, where his research focuses on electromagnetic scattering and remote sensing. е-mail: 16tran(at)cardinalmail.cua.edu
		Victor Frenkel received his Bachelors degree in Agriculture in 1991 from the Hebrew University in Rehovot, Israel. He then completed his Masters in Life Sciences in 1995 at Tel Aviv University in Tel Aviv, Israel, and his PhD in 1999 in Agricultural Engineering at the Technion, Israel Institute of Technology, in Haifa, Israel. He spent the next four years as a senior post-doctoral fellow at the University of Maryland’s Biotechnology Institute in Baltimore, MD. This was followed by eight as years as a staff scientist at the Dept. of Radiology and Imaging Sciences at the Clinical Center, National Institutes of Health in Bethesda, MD. He is presently an Associate Professor of Biomedical Engineering at Catholic University’s School of Engineering in Washington, DC. Dr. Frenkel’s research is in the field of therapeutic ultrasound, where his interests range from ultrasound induced bio-effects to devices and novel methodologies to evaluate them. е-mail: frenkel(at)cua.edu