Epicardial fat causing pitfalls in CT and MR imaging of the pericardium.

To study the complex anatomy of the pericardium and the pericardial recesses, notably the transverse sinus and the recess behind and under the common pulmonary artery, cryomicrotomy sections of 4 frozen cadaver specimens were correlated with CT and MR imaging in multiple planes. In addition, CT chest studies of 254 patients and MR chest studies from 78 patients were reviewed. Epicardial fat interposed between the transverse sinus of the pericardium and the ascending aorta was a normal finding confirmed by cryomicrotomy studies and seen by CT in 23 of 245 patients and in MR imaging in 3 of 78 patients. Epicardial fat indenting the pericardial sac below the common pulmonary artery caused an inhomogeneous signal, mimicking lymphadenopathy on coronal T1 weighted MR images in 4 patients.