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Original Research |
1 Department of Radiology, Indiana University School of Medicine, 550 N
University Blvd., UH 0279, Indianapolis, IN 46202.
2 Department of Pathology, Indiana University School of Medicine, Indianapolis,
IN.
OBJECTIVE. The objective of our study was to determine the usefulness of the apparent diffusion coefficient (ADC) of liver parenchyma for determining the severity of liver fibrosis.
MATERIALS AND METHODS. This study investigated 78 patients who underwent diffusion-weighted imaging (DWI) with 1.5-T MRI and pathologic staging of liver fibrosis based on biopsy. DWI was performed with b values of 50 and 400 s/mm2. ADCs of liver were measured using 2.0- to 3.0-cm2 regions of interest in the right and left lobes of the liver; the mean ADC value was used for analysis. Pathologic METAVIR scores for liver fibrosis stage were used as a reference standard.
RESULTS. The mean ADC values for fibrosis pathologically staged
using the METAVIR classification system as F0 (n = 11), F1
(n = 16), F2 (n = 10), F3 (n = 14), and F4
(n = 27) were 125.9, 105.0, 104.5, 103.2, and 99.1 x
10-5 s/mm2, respectively. The correlation between the
ADC values and the degree of liver fibrosis was moderate (Spearman's test,
= –0.36). There was a significant difference in ADC values between
patients with nonfibrotic liver (F0) and those with cirrhotic liver (F4)
(p = 0.008). The best cutoff ADC value to distinguish between these
groups was 118 x 10-5 s/mm2. However, ADC values
were not useful for differentiating viral hepatitis patients with F2 fibrosis
or higher from those with a lower degree of fibrosis (area under the receiver
operating characteristic curve [AUC] = 0.66) or for differentiating low-stage
fibrosis in all patients from high-stage fibrosis in all patients (AUC =
0.54).
CONCLUSION. The ADCs in cirrhotic livers are significantly lower than those in nonfibrotic livers. However, ADC values measured using the current generation of scanners are not reliable enough to replace liver biopsy for staging hepatic fibrosis.
Keywords: apparent diffusion coefficient cirrhosis diffusion-weighted imaging liver fibrosis MRI
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