Relevance of b‐values in evaluating liver fibrosis: A study in healthy and cirrhotic subjects using two single‐shot spin‐echo echo‐planar diffusion‐weighted sequences

Abstract

Purpose:To investigate the relevance of increasing b-values in evaluating liver fibrosis through the agreement of two diffusion-weighted (DW) sequences. Materials and Methods:A total of 29 cirrhotic patients and 29 healthy volunteers were studied on a 1.5T system. Two single-shot spin-echo echo-planar sequences were acquired using sets of increasing b-values: 0, 150, 250, and 400 seconds/mm 2 (first sequence: DW1a) and 0, 150, 250, 400, 600, and 800 seconds/mm 2 (second sequence: DW2a). Apparent diffusion coefficients (ADCs) of the hepatic parenchyma were calculated on ADC maps. Noisescaled single-point ADCs were calculated for each sequence from b ϭ 400 seconds/mm 2 .Results: ADCs resulted significantly lower in cirrhotic patients compared to controls using both DW1a (mean 1.14 Ϯ 0.20 ϫ 10 2 /second vs. 1.04 Ϯ 0.18 ϫ 10 Ϫ3 mm 2 /second; P ϭ 0.0089). DW1 and DW2, respectively significantly differed in diagnostic performance at receiver operating characteristic (ROC) curve analysis (P ϭ 0.003), showing AUCs of 0.93 (sensitivity 89.7%, specificity 100%) and 0.73 (sensitivity 62.1%, specificity 79.3%), respectively. Noise-scaled single-point ADCs showed a progressive convergence to similar values in cirrhotic and healthy livers at b ϭ 800 seconds/mm 2 (1.12 Ϯ 0.27 ϫ 10 Ϫ3 mm 2 /second vs. 1.13 Ϯ 0.17 ϫ 10 Ϫ3 mm 2 /second). Conclusion:A DW sequence is accurate in assessing liver fibrosis using intermediate (400 seconds/mm 2 ) rather than high (800 seconds/mm 2 ) maximum b-values, but after proper recalculation of ADCs the effects of perfusion rather than diffusion should be considered responsible for the higher accuracy at lower b-values.

Diffusion-weighted Imaging of the Liver with MultiplebValues: Effect of Diffusion Gradient Polarity and Breathing Acquisition on Image Quality and Intravoxel Incoherent Motion Parameters—A Pilot Study

“…The ADC value is strongly dependent on the distribution of b values used to acquire images. For example, Girometti et al (19) showed that use of lower b values (400 sec/mm 2 ) enables better fibrosis detection, an effect attributed to perfusion components at lower b values. The advantage of IVIM is the separation of D (a marker of tissue structure) from perfusion effects, including PF, which depicts vascular volume, and D*, which is an estimation of capillary blood flow velocity (1-3,22).…”

Utility of Apparent Diffusion Coefficients in the Evaluation of Solid Renal Tumors at 3T

“…This reduction in the ADC can results from any source of incoherent motion, particularly capillary perfusion. [32][33][34][35] Our study had several limitations. First, our sample size was small.…”

Efficacy of diffusion-weighted magnetic resonance imaging in the evaluation of extrahepatic cholestasis-related hepatic fibrosis

“…However, in our study, we detected that ADC values had higher sensitivity and specificity rates in the differentiation of the same fibrosis stages. (31). It is known that hepatic perfusion is substantially decreased in cirrhotic patients compared to healthy people (34).…”