NDLI: New acoustic beams designed for rapid lesion formation: limitations near the skin during multiple lesion treatments

Content Provider	IEEE Xplore Digital Library
Author	Hunt, J.W. Xuan, A.Y. Seto, E. Worthington, A.E. Chen, L. Kolios, M.C. Sherar, M.D.
Copyright Year	1997
Description	Author affiliation: Dept. of Med. Biophys., Toronto Univ., Ont., Canada (Hunt, J.W.)
Abstract	Minimally invasive surgery by intense focused ultrasound beams producing defined lesions is being studied extensively by different groups. Lesion formation from a single pulse, depending on treatment time, tissue temperature, and pulse repetition of about 1 minute, should produce little damage near the skin. However, this scheme results in unacceptably long treatment times when used on larger tumors. A possible solution is to generate more rapid treatment times, or larger lesion volumes per pulse. However, hyperthermic temperatures in the overlying normal tissues including the skin may limit these treatments. In a previous presentation, simulations using an "ideal" transducer, pulses as short as 4 s and rapid stirring of the coupling bolus would reduce the temperature rise near the skin. Thus pulse repetitions as short of 10 s would be acceptable. However, real transducer beams show large aberrations which can greatly increase the near-field intensities, and make them unacceptable for hyperthermia therapy. Some artifacts are be caused by clamping of the transducer, others are related to thickness variations of the transducers which generate heterogenous phase shifts from different parts of the transducer which produce unwanted spreads at beam's focus. The authors present detailed amplitude and phase scans near different transducers demonstrating the artifacts, and confirm them using novel ultrasound/magnetic-resonance phantoms showing the measured temperatures at the focus, and at 1 cm depth from the "skin" where the heating is considerably larger than that predicted by theory. Finally, we will discuss solutions for problems in the near field by improving the transducer mounting and reducing the unwanted phase shifts.
Starting Page	1373
Ending Page	1376
File Size	304249
Page Count	4
File Format	PDF
ISBN	0780341538
ISSN	10510117
DOI	10.1109/ULTSYM.1997.661832
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1997-10-05
Publisher Place	Canada
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Acoustic beams Lesions Ultrasonic transducers Skin Minimally invasive surgery Ultrasonic imaging Acoustic pulses Hyperthermia Temperature measurement Temperature dependence
Content Type	Text
Resource Type	Article

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