Bone scintigraphy is used for a variety of indications - most commonly to detect bone metastases but also for infection and inflammation such as osteomyelitis and inflammatory arthritides. The radiotracers are all forms of phosphonates (Tc99m-MDP/HDP) and localize to sites of increased osteoblastic activity (with increased blood flow a lesser, secondary mechanism).

In this case, the mucoperiosteal reaction of sinusitis results in increased osteoblastic activity in the paranasal sinus walls which results in the radiotracer uptake seen. The soft tissue inflammation also results in a degree of increased blood flow, which also adds to the radiotracer accumulation.