Noninflammatory entities and the differential diagnosis of positive three phase bone imaging

The greater sensitivity of skeletal imaging over radiography (93% vs. 50%) for the detection of early osteomyelitis is well known. The introduction of the three phase protocol has improved the specificity of skeletal imaging by eliminating various noninfectious entities; however, the occurrence of false-positive studies is not unusual. Four such cases have been observed by the authors in a group of 34 patients suspected of having osteomyelitis and who had positive three phase skeletal imaging. These includes a patient with giant cell tumor, synovial cell sarcoma, gouty arthritis, and Reiter's syndrome. A description of these cases and a brief review of several other entities associated with positive three phase bone imaging is the subject of this atlas article, which should serve as an aid in the differential diagnosis of this commonly performed scintigraphic procedure.