(A) Anterior and posterior whole-body bone scan demonstrates increased activity in the right posterior elements at L5 (arrow). Mild multifocal growth plate activity suggests a skeleton nearing maturity. Partial infiltration of the injected dose is noted at the right antecubital fossa. (B) Axial and coronal SPECT images further localize the focally increased activity to the right L5 pars interarticularis (arrow).

Differential Diagnosis

•  Pars fracture: Increased uptake at the pars interarticularis makes this the most likely diagnosis in light of the history.

•  Osteoid osteoma: