Integrated reflection coefficient correction with respect to surface inclination and axial distance

The integrated reflection coefficient (IRC) has been shown to be an important US parameter for tissue characterization. However, conventional estimation using a planar reference reflector results in considerably prediction errors for defocused and inclined conditions. In this study inclination and axial distance dependence of the IRC was investigated both theoretically and experimentally. Ultrasound backscatter from soft tissues was simulated by Field II. Measurements have been conducted in native cartilage samples and tissue mimicking phantoms at 40 MHz. The dependencies of IRC on the two parameters were approximated by two-dimensional polynomial functions. These results were used as correction models. Valid ranges of transducer-sample distance (TSD) and sample inclination have been estimated and the influence of the correction model on the standard deviation was evaluated by application of the correction models to measurements of native cartilage.