Experimental evaluation of some possible nonlinearity indicators

Timothy A. Bigelow, William D. O'Brien

Research output: Contribution to journalConference articlepeer-review

Abstract

Due to regulatory reasons, the output levels of ultrasound sources for use in medical applications must be known. Currently, this is done by making focal pressure measurements for a very large number of drive voltage amplitudes and then linearly derating the measured pressure levels. In order to reduce calibration times, some have proposed to linearly extrapolate pressures rather than perform direct measurements. However, nonlinear propagation effects corrupt the linear extrapolation and derating procedure. Thus, a reliable indicator of nonlinearity is needed to identify when linear extrapolation/derating would be valid. In this study, eight different nonlinearity indicators were evaluated experimentally in terms of their correspondence to the linear extrapolation error. Spherically focused ultrasound transducers were selected and excited to test the indicators sensitivity to frequency (3-8 MHz), f/# (1 and 2), transducer diameter (1.905 and 5.08 cm), pulse duration (1 and 3 cycles), and pulse phase (0° and 180°). None of the eight nonlinearity indicators yielded consistent results. The lack of consistency resulted from the competing effects of nonlinear absorption and asymmetric distortion, which have yet to be combined into a unified theory. (Supported by NDSEG Graduate Fellowship and NIH HL58218).

Original languageEnglish (US)
Pages (from-to)1391-1394
Number of pages4
JournalProceedings of the IEEE Ultrasonics Symposium
Volume2
StatePublished - Dec 1 2002
Event2002 IEEE Ultrasonics Symposium - Munich, Germany
Duration: Oct 8 2002Oct 11 2002

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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