Diagnosis of liver metastases: value of diffusion-weighted MRI compared with gadolinium-enhanced MRI

The full diagnostic value of diffusion-weighted (DW) MRI in the evaluation of liver metastases remains uncertain. The aim of the present study was to assess the diagnostic accuracy of DW-MRI and contrast-enhanced MRI (CE-MRI) using extracellular gadolinium chelates, with the reference standard established by consensus interpretation of confirmatory imaging and histopathologic data. MR examinations of 51 patients with extrahepatic malignancies were retrospectively reviewed by two independent observers who assessed DW-MRI and CE-MRI for detection of liver metastases. By reference standard, 93 liver lesions (49 metastases and 44 benign lesions) were identified in 27 patients, 11 patients had no liver lesions, and 13 patients had innumerable metastatic and/or benign lesions. There was no difference in diagnostic performance between the two methods for either observer for the diagnosis of metastatic lesions per patient. For per-lesion analysis, sensitivity of DW-MRI was equivalent to CE-MRI for observer 1 (67.3% vs. 63.3%, p = 0.67), but lower for observer 2 (65.3% vs. 83.7%, p = 0.007). By pooling data from both observers, the sensitivity of DW-MRI was 66.3% (65/98) and 73.5% (72/98) for CE-MRI, with no significant difference (p = 0.171). DW-MRI is a reasonable alternative to CE-MRI for the detection of liver metastases.