An in vivo ultrasonic model of liver parenchyma

摘要

Several ultrasonic tissue characterization features are known tondiscriminate pathological from normal tissue in vivo. Previously, thenauthors developed an in vivo attenuation- and backscatter estimationnmethod with each frequency dependent coefficient being reduced to anslope and intercept at central frequency. They derived expressionsnpredicting the standard deviation (SD) of these features, assuming ancommonly used ultrasonic model of liver parenchyma. In its applicationnto in vivo data, the SD of the intercept features was unexpectedly high.nAnother feature, signal-to-noise ratio (SNR), showed a significant biasnrelated to the window size. In this paper, the model is extended withnthe notion of inhomogeneous parenchyma background (IPB). IPB is shown tonbe present in normal liver parenchyma and is statistically described byna noise term with small amplitude and large correlation cell size. Anmethod is presented to estimate the IPB characteristics. The expressionsnpredicting SD are extended, and an expression is derived predicting thenwindow size bias of the feature SNR. The accuracy and precisionnestimated from a large in vivo data set shows good agreement with thenpredictions with the extended model. It is concluded that IPB is anrealistic and relevant phenomenon and should be part of the in vivonultrasonic model of liver parenchyma