Edge Packing Artifact Mimicking Lytic-Sclerotic Lesion in Bone Scan Due to Spontaneous Malfunction of Photomultiplier Tubes in the Gamma Camera.

Edge packing is a kind of nonuniformity artifact, which usually appears as an accumulation of counts at the edge of the field of view compared to the central region. The common causes of edge packing artifact in the image are defective collimator, noncalibrated photomultiplier tube (PMT), and improper adjustment of deflector plates of CRT. We hereby discuss the occurrence of edge packing artifact due to a problem with the PMTs in the anterior head of gamma camera system during acquisition of bone scintigraphy which mimics as pathological lytic-sclerotic lesion during whole-body image at anterior acquisition. The artifact was successfully removed after the replacement of malfunctioning PMTs.