Experimental Test of Extrapolated Acoustic Output Using Single-Element Transducers

To ensure the continued safety of diagnostic ultrasound, accurate measurements of the acoustic output from clinical devices are necessary. The effects of nonlinear propagation can cause the current derating method to substantially underestimate relevant values in tissue. One suggested method to overcome this is to measure acoustic output parameters at low levels and extrapolate to values at full output. Tissue mimicking material were produced from concentrated milk. The samples had low scatter but speed of sound, attenuation, and nonlinear parameter B/A consistent with nonfatty soft tissues. Measurements of acoustic output from single element transducers were conducted at a wide variety of transmit levels in both water and through a path consisting mostly of tissue mimicking material. Results of peak rarefactional pressure and MI/MIE using tissue mimicking material at high pressure levels were consistent with extrapolated derated values from low level measurements in water. This agreement was true for the six measured transducers, which spanned a range of center frequencies from 2.0 MHz to 15.0 MHz. These results indicate that it may be possible to use low level transmit pulses in water, derate the measured values, and extrapolate those results to the higher pressure levels typically used in diagnostic ultrasonography.