Correlation of hepatic fractional extracellular space using gadolinium enhanced MRI with liver stiffness using magnetic resonance elastography

Purpose: To compare MR hepatic fractional extracellular space (fECS) to liver stiffness (LS) with magnetic resonance elastography (MRE) for evaluation of liver fibrosis. Methods and materials: 71 consecutive patients with suspected chronic liver disease underwent standard liver MRI with MR elastography and additional delayed Gd-DTPA-enhanced sequences at 5 and 10 min in order to calculate hepatic fECS (%) and LS (kilopascals, kPa). Two radiologists blinded to clinical history examined MR images and calculated fECS and LS in identical locations for every patient. Interobserver agreement was calculated using the intraclass correlation coefficient. Pearson’s correlation was calculated for LS and fECS measures, as was the area under the receiver operatic curve (AUROC), sensitivity and specificity of fECS to predict liver stiffness ≥2.93 and ≥5 kPa. The sensitivity of fECS for detecting fibrosis was separately analyzed in the subgroup of patients without anatomic findings of cirrhosis. Results: Substantial to excellent interobserver agreement for both LS and fECS measurements was seen with intraclass correlation of 0.88 (95% CI 0.81–0.92) for LS, 0.77 (95% CI 0.66–0.85) for fECS₅ and 0.76 (95% CI 0.64–0.84) for fECS₁₀. A significant correlation was found between MRE and fECS₅ (r = 0.47, p < 0.0001) and fECS₁₀ (r = 0.44, p < 0.0001). The performance of fECS improved for detection of advanced fibrosis (≥5 kPa) with AUROC, sensitivity and specificity of 0.72, 38%, and 94% for fECS₅ and 0.72, 67%, and 66% for fECS₁₀. Conclusion: fECS correlates modestly with MRE-determined LS. fECS at MRI is a simple calculation to perform and may represent a practical way to suggest the presence of fibrosis during routine liver evaluation.