title: Evidence for ultrasonic finite-amplitude distortion in muscle using medical equipment.
abstract: Finite-amplitude distortion of ultrasonic waves from medical equipment has been observed to occur following transmission through calf muscle in human volunteers. Measurements were made using both dynamic pulse-echo imaging equipment and physiotherapy equipment. In both cases irradiation was carried out under operating conditions commonly used clinically. Pressure waveforms were measured at the skin surface using a broadband polyvinylidene difluoride membrane hydrophone. Using a pulsed, weakly focused 2.5-MHz beam with input peak pressure of 0.8 MPa and a pressure gain of 5.3 at the focus, the mean second harmonic peak magnitude (16 measurements) was 17 dB below the fundamental peak. A 1.1-MHz continuous wave therapy set with input peak pressure of 0.5 MPa showed mean second harmonic magnitude 23 dB below the fundamental.
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000502:physiology*; D011312:Pressure; D014160:Transducers, Pressure; D014465:Ultrasonics