Imaging of the spleen: CT with supplemental MR examination.

Splenic lesions tend to be small or infiltrating and vary in size and configuration, making detection difficult, particularly without use of an organ-specific contrast agent. The authors present a series of selected cases to show the value of computed tomography (CT) and magnetic resonance (MR) imaging in depiction of splenic disease. Six major categories are presented: (a) inflammatory disease, (b) splenic cysts, (c) infarction, (d) nonneoplastic and noninfectious diffuse splenic disease, (e) benign tumors, and (f) malignant tumors. CT attenuation of splenic tissue is homogeneous, typically measuring 40-60 HU on non-contrast material-enhanced scans. Splenic attenuation is normally 5-10 HU less than that of liver, a standard of reference used in evaluation of either hepatic or splenic disease. On T1-weighted MR images, the normal signal intensity of the spleen is less than that of hepatic tissue and slightly greater than that of muscle. On T2-weighted images, the spleen shows higher signal intensity, appearing brighter than the liver. CT is currently the choice for evaluation of the spleen; however, MR imaging may be increasingly used as newer pulse sequences and organ-specific contrast agents are developed.