Features include: increased hepatic echogenicity hyperattenuation of the beam mild or absent positive mass effect geographic borders no distortion of vessels inability to visualize the portal vein walls (as the parenchyma is as bright as the wall) CT decreased attenuation (non-contrast CT) normal liver 50 - 57 HU decreases by 1.6 HU per mg of fat in each gram of liver decreased attenuation (post-contrast CT) liver and spleen should normally be similar on delayed (70 seconds) scans earlier scans are unreliable as the spleen enhances earlier than the liver (systemic supply rather than portal) MRI MRI is the imaging modality of choice in any case where the diagnosis is felt to be less than certain increased T1 signal signal drop-out on opposed-phase imaging ability to quantify the fat fraction Differential diagnosis When located in characteristic locations then there is usually little difficulty in making the correct diagnosis.