A three-phase technetium Tc-99m bone scan is used in CRPS evaluation.

• A. True
• B. False
• C. Not used
• D. Occasionally used

Answer: (A)

In CRPS evaluation, a three-phase Tc-99m bone scan is used because it provides information about blood flow, tissue perfusion, and subsequent bone remodeling in the affected limb. This can be helpful especially when the clinical picture is uncertain early in the disease, since CRPS often involves vasomotor changes and increased osteoblastic activity on imaging.

During the early phase, increased perfusion and pooling of tracer can be seen in the affected extremity due to hyperemia. In the delayed (bone) phase, there may be heightened uptake in involved bones from osteoblastic activity. These patterns can support the diagnosis of CRPS in the appropriate clinical context, but they are not specific to CRPS and findings can be absent or nonspecific in some patients. Imaging is a useful adjunct, not a stand-alone diagnostic criterion.