Effects of Diffraction on Measurements of the Frequency-Dependent Ultrasonic Attenuation

Using a one-dimensional model of wave propagation, the ultrasonic attenuation can be estimimated from spectral analysis of RF A-scans. The results of computer modeling studies and measurements on tissue equivalent phantoms indicate that spectral analysis methods are accurate only in the regime where a one-dimensional model is adequate. In the near field of a typical B-scan transducer, a one-dimenional model is not an accurate description of wave propagation. A simple processing method is presented that minimizes near field diffraction effects on estimates of the slope of the attenuation coefficient as a function of frequency.