TESTS OF BACKSCATTER COEFFICIENT MEASUREMENT USING BROAD-BAND PULSES

An adaptation to a data reduction method is outlined for determining b ackscatter coefficients, eta when broad bandwidth pulses are employed. The accuracy of these eta values is assessed with well-characterized phantoms, which have independently calculated backscatter coefficients based on their physical properties. One phantom produces Rayleigh-lik e scattering, where the backscatter coefficient varies smoothly with f requency over the analysis bandwidth. A second phantom exhibits local maxima and minima in the scattering function versus frequency due to p resence of millimeter sized graphite gel spheres in a gel background. The method was found to produce accurate results using time gate durat ions as small as 2 mus, although better accuracy is obtained for longe r gate durations, particularly when the sample exhibits resonance peak s in backscatter versus frequency. Use of a Hamming window in place of a rectangular window extends the accuracy near the upper and lower li mits of the frequency range.