False positive pericardial effusion due to breast attenuation in multi-gated acquisition (MUGA) scan

Objectives MUGA scans are used to evaluate the left ventricle function and pericardial anatomy. A photopenic “U-halo” around the cardiac blood pool in the left anterior oblique (LAO) view is commonly seen with pericardial effusion. We describe findings of false positive pericardial effusion due to breast attenuation in cancer patients.

Methods Several cases that demonstrated the photopenic “U-halo” in the LAO view did not have true pericardial effusion. The patients' breast size and how far the breast sagged in reference to the heart silhouette were visually observed in topograms. The oblique tilt position was evaluated to determine the effect it may have in creating the photopenic “U-halo”. A unique MUGA case demonstrating collateral vessels in bilateral breasts was used as a reference marker image to determine the effect of a slightly more anterior versus left lateral oblique tilt in the LAO view.

Results Large breasts can overlie the heart in the LAO projection. The overlying breast can cause the appearance of pericardial effusion in the resulting image by attenuating tissues surrounding the heart. The positioning of the breast also affected the appearance of the photopenic halo. A patient with tissue expanders having more upright breasts demonstrated a photopenic area anterior to the left ventricle whereas a large breast that sagged more laterally demonstrated no photopenic area.

Conclusions Patients with large breasts may show a photopenic “U-halo” in the LAO view dependent on how far the breast sags in reference to the heart silhouette and on the positioning of the oblique tilt. The anterior image should be used to determine breast attenuation versus a photopenic area surrounding the heart. If both the anterior and LAO view demonstrates the “U-halo”, taking another view with a slightly more anterior or lateral oblique position will demonstrate inconsistency of the photopenic area thereby excluding diagnosis of pericardial effusion