Quantitative ultrasound methods for the assessment of liver steatosis using controlled attenuation parameter as reference method

Objectives Liver steatosis can progress to nonalcoholic steatohepatitis and liver cirrhosis, becoming one of the leading indications for liver transplantation. Therefore, early detection and staging of steatosis is very important. In addition to Transient Elastography (TE) with Controlled Attenuation Parameter (CAP), several methods were developed for steatosis assessment. The aim of our study was to evaluate the feasibility of two new quantitative ultrasound (QUS) parameters, TSI (tissue scatter-distribution imaging) and TAI (tissue attenuation imaging) for steatosis diagnosis considering CAP as reference. Materials A prospective study was conducted in which liver steatosis was assessed in 67 patients (65.7% men, mean age 55.6 ± 13.2 years), evaluated in the same session by QUS and CAP implemented on the following systems: Samsung Medison RS85 (CA1-7A probe) and FibroScan Compact M 530 (M and XL probes), respectively. For CAP, reliable measurements were defined as the median value of 10 measurements with IQR/M<0.3. For QUS, five consecutive measurements of TAI and TSI were acquired by a color-coded map overlaid on B-mode ultrasound. Attenuation coefficient and scatter-distribution coefficient were automatically calculated and reliable measurements were defined as an reliability index, R2 over 0.6. The cut-off value by CAP for identifying the presence of at least mild steatosis was 248 dB/m [1]. Results Reliable measurements by CAP and TAI/TSI were obtained in 100% of cases. Moderate correlations between steatosis assessment methods were observed: TAI vs. CAP r=0.67, TSI vs. CAP r=0.53, TSI vs. TAI, r=0.63.  The best cut-off value for TAI to identify at least mild steatosis was > 0.66 (AUROC=0.87, p<0.0001, Se=81.2%, Sp=84.2%, PPV=92.9%, NPV=64%). The best cut-off value for TSI for identifying at least mild steatosis was > 96.2 (AUROC=0.81, p<0.0001, Se=81.2%, Sp=84.2%, PPV=88.6%, NPV=64%). Conclusions TAI and TSI are feasible methods for assessing liver steatosis, which moderately correlate with CAP measurements.