Experimental validation of a diffraction correction model for high frequency measurement of ultrasound backscatter coefficients

Diffraction correction functions are assessed using a tissue equivalent calibrated phantom and compared to the theoretical model of Chen et al. (UFFC: 44; 515-525, 1997). Two transducers were evaluated: (1) 50 MHz, focal distance at 5.7 mm and f/number of 1.7 and (2) 29 MHz, 10.0 mm and f/2, respectively. The RF backscattered signals from a well calibrated tissue equivalent phantom were compensated for attenuation, squared and filtered, providing the backscattered power as a function of the penetration depth. A polynomial function was fitted and normalized to its peak, resulting in the experimental diffraction correction function. Over a region centered at the focus and corresponding to 25% of the focal distance, the RMS error between Chen´s theoretical computation and experimental diffraction correction functions was 3.4% (50 MHz) and 4.3% (29 MHz). Between theoretical and the plane reflector cases the RMS error was; 17.6% (50 MHz) and 10.1% (29 MHz). Chen´s theory is an accurate and useful means to correct ultrasound backscatter measurements in the high frequency range