Hyperechoic liver nodules: characterization with proton fat-water chemical shift MR imaging

To evaluate proton fat-water chemical shift fast low-angle shot magnetic resonance (MR) imaging for differentiation of fat-containing hyperechoic liver nodules from hyperechoic liver nodules without a fatty component.

T1-weighted fast low-angle shot fat-water chemical shift gradient-echo MR imaging was performed in 96 patients without cirrhosis with 138 hyperechoic liver nodules. In-phase and opposed-phase breath-hold images were acquired. The percentage of signal intensity variation between in-phase and opposed-phase images and the spleen-to-lesion contrast ratio were used to differentiate liver nodules.

Chemical shift MR images showed fat in 15 (11%) hyperechoic nodules (two angiomyolipomas and 13 nodular fatty infiltrations of the liver). The mean percentage of signal intensity variation between in-phase and opposed-phase images was 156% (standard error, 43.5%) in nodules with fat and -0.16% (standard error, 0.96%) in nodules without fat (P = .003). Spleen-to-lesion contrast was similar on in- and opposed-phase images in lesions without fat (mean difference, -0.0107; standard error, 0.012), whereas the mean difference in fat-containing nodules was 0.805 (standard error, 0.225; P = .003). The area under the receiver operating characteristic curve was 0.97 for signal intensity variation.

Hyperechogenicity in certain liver nodules is caused by fat. Chemical shift MR imaging allows accurate differentiation between these and other hyperechoic lesions with no fat component.