The Technetium-99 bone scan is the most common. It can be done as just a one view study or in a three phase one. The one time view is very good for detecting metastases from tumors. A 3 phase study is done so that the soft tissues can also be looked at. It can be used to look at stress reactions in the tibia, for complex regional pain syndrome I (formerly called RSD - reflex sympathetic dystrophy), and for infection.
Other nuclear medicine studies are designed to look for specific things. For infection, there is the white cell tagged study or indium scan, and the gallium scan. The indium scan is usually used for infection detection. In this study, a blood sample is taken from the patient and the white cells are separated out. These WBCs are then tagged with indium and injected back into the patient. As you probably know, white cells attack infection. So, the WBCs usually migrate and collect in an infected area.
Gallium can be used for infection or tumor detection. It, however, is usually used in conjunction with the Technetium scan. Depending upon what the two studies show, then determines the chances of the increased uptake being an infection or not.
So, there are several tests that can be done and it is basically up to the referring physician, as to what information he/she wants to obtain. Bone scans are usually used in conjunction with other imaging studies (x-rays, CT scan, MRI, ultrasound) and lab work.