Hi,
In a whole body bone scan, a radioactive dye, called tracer, is injected into the patient and then the scan is done immediatly and after 2 hours. The tracer attaches itself to the area of the bone with rapid changes. A special camera then takes images of these areas. The problamatic areas will show as dark areas in the film. A bone scan is used to localise specifically where the problem lies. Then further tests are done for the disease and treated accordingly. In your father's case, the bone scan will help in localising the exact spot on the pelvis where sclerosis is suspected.
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regards
Dr. Gupta