An in vivo ultrasonic model of liver parenchyma

Several ultrasonic tissue characterization features are known to discriminate pathological from normal tissue in vivo. Previously, the authors developed an in vivo attenuation and backscatter estimation method and derived expressions predicting the standard deviation (sd) of the intercept and slope features, assuming a commonly used ultrasonic model of liver parenchyma. In its application to in vivo data the sd of the intercept features was unexpectedly high and the feature SNR (signal to-noise ratio) showed a significant bias related to the window size. In this paper, the model is extended with the notion of inhomogeneous parenchyma background (IPB). IPB is shown to be present in normal liver parenchyma and is statistically described by a noise term with small amplitude and large correlation cell size. The effect of the noise term on the features can be predicted. The results demonstrate good agreement between the estimations and predictions in in vivo data. It is concluded that IPB is a realistic and relevant phenomenon and should be part of the in vivo ultrasonic model of liver parenchyma.