What is a three-phase bone scan?
A three-phase scan evaluates blood flow to a particular area of the musculoskeletal system during the first few minutes of imaging and then soft tissue uptake (20–30 minutes following injection). A delayed third phase is acquired 2 to 4 hours later. Areas of increased blood flow will have increased activity in first two phases of imaging, while areas of bony remodeling will have increased uptake and thus activity in third (delayed imaging) phase ( Table 8.4 ). Bone scans are highly sensitive to abnormalities of bone (including fracture, infection, tumor, and arthritis) but are nonspecific. The entire skeleton may be imaged, thus making the technique useful in the detection of metastatic lesions.