Detection, classification, and characterization of focal liver lesions: Value of diffusion-weighted MR imaging, gadoxetic acid-enhanced MR imaging and the combination of both methods

Aim: To evaluate diffusion-weighted MR imaging (DWI), gadoxetic acid-enhanced MR imaging and the combination of both methods in the detection, classification, and characterization of focal liver lesions (FLL). Methods: A total of 119 FLL (28 HCCs, 39 metastases, 15 FNHs, 11 adenomas, 13 hemangiomas, 13 cysts) were retrospectively analyzed in 36 patients. In those patients MR imaging of the liver comprising respiratory-triggered DWI (b values of 50, 300, and 600 s/mm2) and gadoxetic acid-enhanced MR imaging including image acquisition in the hepatocyte-selective phase (20 min post injection) had been performed. Three image sets were assigned and compared: DWI only (set A), gadoxetic acid-enhanced MR imaging only (set B), and both modalities in combination (set C). Two readers independently interpreted the images in random order. For each reader and image set, the area under the receiver operating characteristic curve (Az) and sensitivity in the detection of FLL was determined as well as the accuracy in the classification and characterization of FLL. Results: There was no significant difference between the three image sets in the detection of FLL with regards to Az. However, when only lesions with a diameter of 10 mm or less were analyzed, the Az values of set C were significantly higher than those of sets A and B for both readers. For classifying and characterizing FLL both set B and C were significantly superior to set A. Conclusion: Adding DWI to gadoxetic acid-enhanced MR imaging significantly increases the accuracy in the detection of small FLL.