Estimation of Hepatic Extracellular Volume Fraction Using Multiphasic Liver Computed Tomography for Hepatic Fibrosis Grading

The purpose of this study was to determine whether hepatic extracellular volume fractions (fECVs) measured using multiphasic liver computed tomography (CT) can be used to quantify the severity of hepatic fibrosis (HF).This retrospective study was approved by our institutional review board, and the requirement for informed consent was waived. A total of 141 patients (male-female ratio, 109:32; mean [SD] age, 59.4 [11.4] years) histologically diagnosed with HF (F0-F1 = 33 and F2-F4 = 108) underwent multiphasic liver CT. Absolute enhancements (in Hounsfield unit) of the liver parenchyma (Eliver) and aorta (Eaorta) 3 minutes after contrast administration were measured on subtraction images of precontrast and equilibrium phase scans using nonrigid registration software. The fECV was calculated using the following equation: fECV (%) = Eliver/Eaorta × (100 - Hematocrit [%]). Correlation between fECV and HF stage was evaluated using the Spearman correlation coefficient. The fECVs were compared between F0-F1 and ≥F2 as well as between child A and child B or C. Diagnostic performance of fECV in predicting significant HF (≥F2) was assessed using receiver operating curve analysis.The fECVs showed a significant correlation with pathologic HF staging (r = 0.493, P < 0.001). The F2-F4 showed significantly higher fECVs than did F0 to F1 (33.6% [4.7%] vs 27.7% [4.4%]; P < 0.001). The fECVs were significantly higher in the patients with child B or C than those with child A (35.2% [7.0%] vs 31.3% [4.2%]; P < 0.001). The fECV values higher than 28.76% provided 87.5% sensitivity and 71.0% specificity in detecting significant HF (area under the curve, 0.832; P < 0.0001).Because fECV was shown to increase along with HF progression, the estimation of fECV using routine multiphasic liver CT may have the potential to detect significant HF.