Estimation of Acoustic Attenuation in Diffuse Liver Disease: Can it be Done with the Zero-Crossing Technique?
In-vivo attenuation measurements of the liver have been obtained in 41 patients with diffuse liver disease, 8 normal controls and a liver phantom. Using a spectral shift approach, a parameter S (in MHz/cm), the slope of zero-crossings of A-line data vs. depth was measured to estimate the slope of the attenuation coefficient with frequency, denoted by β (in dB/cm-MHz). 1 MByte of digitized data per ultrasound procedure and per liver was used to estimate the slope S. Three different acoustic transducers were used. The patients were classified by histopathological structure following blind readings of liver needle biopsies.
No correlation was found between the degree of portal fibrosis or fat and the estimate of the acoustic attenuation. The observed range of attenuation estimates in 8 normal controls was 0.23–0.73 dB/cm MHz using three different transducers. The variability in controls was similar to the variability in a liver tissue equivalent phantom. No statistical significant difference in slope of attenuation for five disease groups compared to each other and controls was found. We conclude that a spectral shift technique using small amounts of digitized data for liver is inadequate to estimate acoustic attenuation in liver.
KeywordsPrimary Biliary Cirrhosis Portal Fibrosis Acoustic Attenuation Diffuse Liver Disease Liver Needle Biopsy
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