Abnormalities on cardiac planar projection and tomographic images: focus on pericardial effusions.

Careful, systematic inspection of planar projection and tomographic images is essential as extracardiac findings and non-perfusion abnormalities may be present and on occasion account for the patient's symptoms. Two case histories and the corresponding images are presented below in which a stress myocardial perfusion single photon emission computed tomography (SPECT) study was performed and the diagnosis of a pericardial effusion was made. Although pericardial effusions are typically diagnosed by other imaging modalities (echocardiography and computed tomography) they can also be identified by radionuclide imaging techniques. Findings on planar projection and gated SPECT include the appearance of a "halo" of reduced tracer concentration surrounding the heart on both the rest and stress planar projection and tomographic images, and a "rocking" motion of the heart on gated images.