(Tuesday, 7/31/2018) 10:00 AM - 10:30 AM
Room: Exhibit Hall | Forum 6
Purpose: To evaluate the degree of liver fibrosis in patients with liver biopsy based on statistical chi-square analysis of heterogeneity of liver tissue texture on ultrasound images.
Methods: This retrospective study was IRB approved. Ultrasound images of right lower lobe (RLL) of thirty-one patients (22 M, 9 F; 17-81 y; F0-3: 16; F4-6: 15) who underwent non-targeted ultrasound guided biopsy were analyzed using an in-house Matlab program. A user manually selected a primary ROI in the range of 4-6 cm (avoiding non-hepatic parenchyma). Local variances, σ², of several texture features (e.g., image intensity, image gradient) were calculated in 25x25 pixel secondary ROIs in a roster scan fashion. The primary ROI contains a large number of secondary ROIs to maintain the precision of statistical analysis. The global variances, σ₀², of the texture features were estimated theoretically from the local average intensities and image gradients using the property of Rayleigh distribution. The χ²(=σ²/σ₀²) were calculated and plotted on a histogram. Several statistical descriptors were extracted from the histogram and entered in statistical analysis.
Results: The χ² measures the degree of similarity of liver tissue texture between a secondary ROI and the primary ROI. In none to low grade fibrosis, χ² histogram of image gradient has a wide distribution with a peak at 1/SNR. In chronic fibrotic liver, the χ² histogram of image gradient has a narrow distribution and the peak value decreases dramatically in advanced fibrosis (F4-6 vs. F0-3, p<0.001, AUC=0.985, sensitivity=93.7%, specificity=93.3%). There is a strong negative correlation between the peak value and fibrosis stage (r=-0.79).
Conclusion: Liver tissue texture appears distinctly heterogeneous on B-mode abdominal ultrasound in advanced fibrosis than in none to low grade fibrosis. THA based on regional texture analysis and χ² test can detect this change with high sensitivity and specificity in this pilot study.
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