Clinical Implications of Non-Steatotic Hepatic Fat Fractions on Quantitative Diffusion-Weighted Imaging of the Liver

Hildebrand Dijkstra,Astri Handayani,Peter Kappert,Paul E Sijens,Matthijs Oudkerk

doi:10.1371/journal.pone.0087926

Hildebrand Dijkstra, Astri Handayani + Show 3 more

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https://doi.org/10.1371/journal.pone.0087926

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Abstract

Diffusion-weighted imaging (DWI) is an important diagnostic tool in the assessment of focal liver lesions and diffuse liver diseases such as cirrhosis and fibrosis. Quantitative DWI parameters such as molecular diffusion, microperfusion and their fractions, are known to be affected when hepatic fat fractions (HFF) are higher than 5.5% (steatosis). However, less is known about the effect on DWI for HFF in the normal non-steatotic range below 5.5%, which can be found in a large part of the population. The aim of this study was therefore to evaluate the diagnostic implications of non-steatotic HFF on quantitative DWI parameters in eight liver segments. For this purpose, eleven healthy volunteers (2 men, mean-age 31.0) were prospectively examined with DWI and three series of in-/out-of-phase dual-echo spoiled gradient-recalled MRI sequences to obtain the HFF and T2*. DWI data were analyzed using the intravoxel incoherent motion (IVIM) model. Four circular regions (ø22.3 mm) were drawn in each of eight liver segments and averaged. Measurements were divided in group 1 (HFF≤2.75%), group 2 (2.75< HFF ≤5.5%) and group 3 (HFF>5.5%). DWI parameters and T2* were compared between the three groups and between the segments. It was observed that the molecular diffusion (0.85, 0.72 and 0.49 ×10−3 mm2/s) and T2* (32.2, 27.2 and 21.0 ms) differed significantly between the three groups of increasing HFF (2.18, 3.50 and 19.91%). Microperfusion and its fraction remained similar for different HFF. Correlations with HFF were observed for the molecular diffusion (r = −0.514, p<0.001) and T2* (−0.714, p<0.001). Similar results were obtained for the majority of individual liver segments. It was concluded that fat significantly decreases molecular diffusion in the liver, also in absence of steatosis (HFF≤5.5%). Also, it was confirmed that fat influences T2*. Determination of HFF prior to quantitative DWI is therefore crucial.

Highlights

The effect of fat on the self-diffusion of water has been assessed since the onset of nuclear magnetic resonance
diffusion weighted imaging (DWI) reflects the mobility of water molecules in a tissue which can be described by the apparent diffusion coefficient (ADC) or the intravoxel incoherent motion (IVIM) model [4,5,6]
Since DWI has been successfully applied in the assessment of focal liver lesions and diffuse liver diseases such as cirrhosis, fibrosis and steatosis [7,8,9,10,11]

Summary

Introduction

The effect of fat on the self-diffusion of water has been assessed since the onset of nuclear magnetic resonance. Since DWI has been successfully applied in the assessment of focal liver lesions and diffuse liver diseases such as cirrhosis, fibrosis and steatosis [7,8,9,10,11]. In an animal study it was concluded that steatosis may confound determination of hepatic fibrosis with DWI [12]. This was confirmed in two clinical studies where the ADC decreased significantly in patients with hepatic steatosis [13,14]. A study which applied the IVIM model demonstrated that steatosis can reduce the molecular diffusion significantly and act as a potential confounder when IVIM is used to assess diffuse liver diseases such as cirrhosis [15]

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