Figure 4a.

Fibrotic scars devoid of fat in a patient with end-stage liver disease due to cystic fibrosis. The patient underwent liver transplantation for hepatic decompensation; ex vivo MR imaging of the explanted cirrhotic liver was performed. (a) Fat fraction map shows the percentage of fat according to proton density in each voxel of the image. The map was obtained by generating multiple gradient echoes at serial out-of-phase and in-phase echo times. As described by Bydder et al (26) and Yokoo et al (27), the signal intensity is modeled as a function of echo time. The modeling takes into account the interference effects between water and fat and also between the various fat moieties while correcting for exponential T2* decay. Most of the liver parenchyma has intermediate signal intensity, with pixel values ranging from 5% to 10% fat content. Several fibrotic scars course through the parenchyma and carve the liver into 1–1.5-cm regenerative nodules. The fibrotic scars have low signal intensity (arrows), which indicates that they are devoid of fat. The gallbladder fossa (gbf) and falciform ligament (FL) contain adipose tissue with very high fractional fat content and therefore appear markedly hyperintense. (b) T2 map shows that the fibrotic scars (arrows) have prolonged T2 relaxation. FL = falciform ligament, gbf = gallbladder fossa.