Quantitative Ultrasound (QUS) strives to enhance conventional ultrasound by providing estimates of attenuation, backscatter, and other acoustic properties of tissue derived from frequency-dependent, backscattered signals. The purpose of this presentation is to describe methodology used to derive QUS parameters when using instruments employed for B-mode imaging. Specially-equipped clinical ultrasound scanners provide beam-formed, radiofrequency echo signals for off-line analysis. Echo signal power spectra are derived from windowed segments of these signals. Echoes from a soft tissue-mimicking reference medium are used to account for system dependencies of the data. Depth-dependent changes in tissue-to-reference medium power-spectra ratios yield the attenuation coefficient in the organ. Further processing provides estimates of the backscatter coefficient; an effective scatterer diameter is derived from the frequency-dependence of backscatter that describes the tissue correlation function. Tests using a variety of clinical ultrasound systems have resulted in good agreement in QUS parameter estimates among data acquired from different scanners. This presentation will focus on applications of QUS in the liver, kidney, and breast. In both organs subjective assessments of echogenicity and beam transmission can be associated with objective, quantitative estimates of backscatter and attenuation. Advanced processing procedures to deal with cases where assumptions of diffuse and stationary scattering are not met, and extension to 3D, will also be discussed.
展开▼
