Ultrasonographic Diagnosis of Nonalcoholic Steatohepatitis Based on the Quantitative Evaluation of the Ultrasound Beam Behavior into the Liver

摘要

Ultrasonography is a simple method in diagnosing nonalcoholic steatohepatitis (NASH), providing useful information, but it is subjective and does not accurately differentiate between steatosis grades. The computerized processing of the data that comprises the ultrasonic image might transform ultrasonography into an objective examination. We aim to study the performance of the quantitative evaluation of the ultrasound beam behavior into the liver in diagnosing NASH and in establishing the fatty load grade. 45 consecutive NASH patients and 17 healthy subjects were prospectively included in this study. We calculated on each image: attenuation, backscattering, correlation coefficient and fitting error, each computed from 7, 11 and 15 pixels. Predictive value and area under the ROC curves (AUROC) were used to assess the accuracy of the results. In distinguishing NASH patients from healthy subjects, AUROC for attenuation, backscattering, correlation coefficient and fitting error were 0.95, 0.95, 0.81 and 0.58 respectively, and in distinguishing significant from insignificant fatty load, AUROC recorded 0.83, 0.82, 0.78 and 0.57 respectively. The number of pixels used to compute these coefficients doesn't have a great impact on their relevance. A cutoff value of -0,08 of ultrasonic-enhanced attenuation could distinguish the presence and absence of steatohepatitis (Sn 86,67%, Sp 100%, PPV 100%, NPV 71,4337%, AUROC 0,957), and a cutoff value of-0,1 could distinguish the moderate/severe from the absent/mild fatty load (Sn 88,89%, Sp 65,71%, PPV 66,65%, NPV 88,46%, AUROC 0,831). The use of these methods could substantially improve the identification of NASH and the assessment of its grade.