Liver fibrosis is considered a major morbidity that can lead to serious complications like portal hypertension and hepatic cellular failure ;thus, it is more wisely to be managed in early stages. It is crucial to determine the stage of hepatic fibrosis as antiviral therapy will be beneficial to cases with ≥ F2 .
Previous researches had reported a relationship between the liver fibrosis and ADC values. The current study used b values 400 and 800 s/mm2. Taouli et al.  stated a significant correlation on using b values of ≥ 500 s/mm2 and Jiang et al. , a meta-analysis concluded that DWI of the liver is a reliable noninvasive diagnostic tool for liver fibrosis staging using bmax ≥ 800 s/mm2.
The literature stated that DW-MRI had demonstrated lower ADC values in liver fibrosis than normal liver [1, 2, 12,13,14,15,16,17,18,19,20]. In concordance with the previous researches, the liver ADC values of the cases were significantly lower than the ADC values of the control group. Regarding the diagnostic performance in distinguishing different stages of fibrosis, Do et al.  had used b values of 0, 50, and 500 s/mm2 and reported cutoff values of 1.68 × 10−3 mm2/s, 1.53 × 10−3 mm2/s, and 1.68 × 10−3 mm2/s for METAVIR stages ≥ F2, ≥ F3, and F4, respectively. Their study group was smaller (34 patients) and inhomogeneous including many etiologies rather than viral hepatitis C.
Lower values for the same stages have been elicited in our study 1.409 × 10−3 mm2/s, 1.192 × 10−3 mm2/s, and 1.093 × 10−3 mm2/s for METAVIR stages ≥ F2, ≥ F3, and F4, respectively using b values of 400 and 800 s/mm2. Bonekamp et al.  have demonstrated cutoff values of 1.33 × 10−3 mm2/s, 1.31 × 10−3 mm2/s, and 1.30 × 10−3 mm2/s to detect METAVIR stages ≥ F2, ≥ F3, and F4, respectively using b values 0 and 750 s/mm2. The number of cases belonging to F2 and F3 stages was notably small (2 cases for F2 and 6 cases for F3). Variable b values and different sample sizes as well as the patient’s characterization regarding different causative entities might explain the difference.
Shayesteh et al.  with b value of 1000 s/mm2 and 1.5 T scanner have reported somehow similar cutoff values 1.223 × 10−3 mm2/s, 1.186 × 10−3 mm2/s, and 1.140 × 10−3 mm2/s to detect METAVIR stages ≥ F2, ≥ F3, and F4, respectively. Also, the AUC 0.908, 0.889, and 0.933 for ≥ F2, ≥ F3, and F4 respectively.
Similarly, Fujimoto et al.  with b values of 0 and 1000 s/mm2 have declared close cutoff values of 1.35 × 10−3 mm2/s (METAVIR ≥ F1), 1.32 × 10−3 mm2/s (METAVIR ≥ F2), 1.27 × 10−3 mm2/s (METAVIR ≥ F3), and 1.23 × 10−3 mm2/s (METAVIR F4).
It is believed that significant periportal fibrosis (F2 stage) is considered a predictor of cirrhosis; thus, the aim of diagnosis and treatment during this stage is to manage the underlying etiology and abort its effect. Besides, high accuracy in the diagnosis of severe fibrosis (F3 and F4) is important, as these patients should be followed up and screened for development of portal hypertension and HCC [22, 23].
Regarding the values of ADC liver for cirrhosis (stage F4 by METAVIR score), our study reported 999.56 ± 81.09 mm2/s (mean ± SD) for 23 cases. Close result was obtained by Verloh et al.  1015 ± 60.2 mm2/s for the same pathological category. But they used another scoring system instead of METAVIR (Ishak score) and a 3 T MRI system.
Again, similar values concerning F4 stage were recorded by Hu et al. , whom used variable b values and 1.5 T scanner. With b value 700 s/mm2 and another scoring system similar to METAVIR, they reported 1150 ± 22 mm2/s.
Our study revealed relatively larger area under the curve (AUC) of normalized ADC liver in diagnosis of significant fibrosis (≥ F2) and cirrhosis (F4) compared to ADC liver; 0.973 and 0.986 compared to 0.968 and 0.940 for ≥ F2 and F4 stages respectively. Thus, it can be considered an excellent diagnostic tool with AUC > 90% .
Shin et al.  compared the diagnostic performance of ADC liver and normalized ADC liver and reported evident difference between them in diagnosing all fibrosis stages, for ≥ F2 0.631AUC, 83.4% sensitivity, 58.5% specificity, and optimal cutoff value was 1.332 × 10−3 mm2/s using liver ADC. Normalized ADC liver for the same category revealed 0.877 AUC, 84.3% sensitivity, 86.9% specificity, and optimal cutoff value was 1.411.
For F4 stage, AUC 0.577, 43.4% sensitivity, 83.1% specificity, and optimal cutoff value was 1.189 × 10−3 mm2/s using liver ADC. Normalized ADC liver for the same category revealed AUC 0.789, 90.2% sensitivity, 62.3% specificity, and optimal cutoff value was 1.365. This might be contributed to variable b values used, and their study group was inhomogeneous including only 3 cases of post hepatitis C fibrosis.
Again, Do et al.  have concluded that normalization of liver ADC using the spleen as a reference organ increased the diagnostic ability for hepatic fibrosis. There was larger AUC for normalized ADC liver in all fibrosis stages 0.864, 0.805, and 0.935 for ≥ F2, ≥ F3, and F4, respectively, compared to 0.655, 0.689, and 0.720 for the same fibrosis categories using the liver ADC. Their sample was heterogeneous in nature as other causes of hepatic fibrosis rather than chronic hepatitis C were included. Also different b values, as they used 0, 50, and 500 s/mm2 b values on 1.5 T machine.