MR imaging of the transverse sinus of the pericardium.

On MR images of the chest, a low-signal-intensity band is often seen between the ascending aorta and left atrium in the transverse plane, and between the right pulmonary artery and left atrium in the coronal and sagittal planes. CT and MR of cadavers, with injection of contrast media into the pericardial space, confirmed that this structure was the transverse sinus of the pericardium. Retrospective review of MR studies in 45 patients without evidence of pericardial disease showed the transverse sinus of the pericardium in 80% (32/40) of transverse ECG-gated images, 78% (7/9) of sagittal ECG-gated images, and 67% (14/21) of coronal ECG-gated images. Nongated studies showed the sinus infrequently. Knowledge of the three-dimensional anatomy of the transverse sinus of the pericardium and of its typical MR appearance should allow its recognition and preclude misinterpretation.