Measurement and correction of ultrasonic pulse distortion produced by the human breast

Ultrasonic wavefront distortion produced by transmission through breast tissue specimens was measured in a two‐dimensional aperture. Differences in arrival time and energy level between the measured waveforms and references that account for geometric delay and spreading were calculated. Also calculated was a waveform similarity factor that is decreased from 1.0 by changes in waveform shape. For nine different breast specimens, the arrival time fluctuations had an average (±s.d.) rms value of 66.8 (±12.6) ns and an associated correlation length of 4.3 (±1.1) mm, while the energy level fluctuations had an average rms value of 5.0 (±0.5) dB and a correlation length of 3.4 (±0.8) mm. The corresponding waveform similarity factor was 0.910 (±0.023). The effect of the wavefront distortion on focusing and the ability of time‐shift compensation to remove the distortion were evaluated by comparing parameters such as the −30‐dB effective radius, the −10‐dB peripheral energy ratio, and the level at which the effectiv...