Confident non-invasive diagnosis of pseudolesions of the liver using diffusion-weighted imaging at 3T MRI.

Purpose: Pseudolesions of the liver including focal steatosis or non-steatosis and THID (transient hepatic intensity differences) are often challenging, especially when imaging patients with underlying malignant disease. We evaluated the efficacy of diffusion-weighted imaging (DWI) in the diagnostic work-up of pseudolesions.
Materials and Methods: Forty-eight patients with pseudolesions of the liver were consecutively examined and the images were retrospectively analyzed. MRI was performed on a clinical 3T scanner using T1-GRE in-phase and opposed phase images, T2-TSE-FS, diffusion-weighted sequences (b-value 50, 300, 600), ADC mapping, and dynamic post-contrast T1-VIBE-FS sequences (32 patients received Gd-EB-DTPA and 16 patients received gadolinium chelates). All images were analyzed by two experienced radiologists in consensus. As a standard of reference, we used the T1-w GRE, in-phase and out of phase, and the contrast enhanced series, as well as long-term follow-up.
Results: In the 48 patients, a total of 116 liver lesions were found. Of these, 40 were benign and eleven were malignant focal lesions. Benign lesions included one FNH, 26 simple cysts, and twelve hemangiomas. In addition, 65 pseudolesions (20 focal steatosis, 13 focal non-steatosis, and 32 THIDs) were found. All pseudolesions could be identified either on the T1-GRE in-phase and opposed phase images or on the contrast-enhanced series, or on both. However, none of them were visible on the diffusion-weighted images.
Conclusion: Pseudolesions are invisible on DWI (negative predictive value = 1); therefore, DWI can be used as an additional sequence to significantly increase diagnostic confidence in the differentiation between pseudolesions and other focal liver lesions.
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