Usefulness of standard deviation on the histogram of ultrasound as a quantitative value for hepatic parenchymal echo...

This study examined whether the standard deviation (SD) values on the histogram measured in the picture archiving and communication system (PACS) views of an ultrasound (US) can be used as an index to determine the homogeneity or heterogeneity of a hepatic parenchymal echo. Patients (n = 202) underwent an abdominal US examination. One US unit was used with a convex (3 to 5 MHz) transducer. The echogenicity of the hepatic parenchyma was measured in four different regions-of-interest (ROIs) of the liver with all vessels, bile ducts and calcification being avoided. The SDs were calculated automatically on the histogram of the ROI in the PACS views. The echo patterns of the liver were classified into normal, fatty liver (FL) and chronic liver disease (CLD). The distribution of the SD calculated from the ROI histogram of these three groups was examined, and statistical analysis for multiple comparisons of the average SD of the three groups was carried out using one-way analysis of variance. Among the 202 patients, there were 72 normal patients (mean SD: 11.10 +/- 0.91), 66 with a FL (mean SD: 11.09 +/- 1.04) and 64 with CLD (mean SD: 14.21 +/- 2.32). The SD values of the normal and FL groups were similar (p > 0.05), but there were significant differences (p < 0.0001) between the CLD and normal groups, and between the CLD and FL groups. The SD values of the abdominal US examination, which had been calculated on the ROI histogram of the PACS view, are believed to reflect the homogeneity or heterogeneity of the hepatic parenchyma. Smaller SD values are thought to represent normal or FL conditions, and larger SD values reflect the possibility of CLD that shows coarse echo. Therefore, it is concluded that the SD can be used as a useful quantitative value that can determine the coarseness of CLD.