Gallium 67 SPECT as a treatment monitoring tool in temporal bone and skull base osteomyelitis

Objectives Evaluate role of Gallium scintigraphy as a treatment monitoring tool in temporal bone and skullbase osteomyelitis.

Methods This IRB approved retrospective study of 10 patients who underwent serial gallium scans at our institution between 2010-2013. A dose of 5 mCi (185 MBq) Gallium citrate was given intravenously followed by 24 hour skull planar and SPECT imaging. Patients were followed for minimum three months. Qualitative and quantitative analysis of initial and post-treatment Gallium SPECT images was performed. Quantitative analysis was done with region of interest (ROI) in bilateral temporal bone or skullbase and lesion to normal ratio calculated.

Results There were 8 males and 2 females with mean age of 63 ±16 years (range: 33 - 84 years). The diagnoses included temporal bone osteomyelitis (3 patients), mastoiditis (3 patients), petrous apicitis (2 patients) and a combination (2 patients). 7 patients had diabetes mellitus. 2 were immunocompromised. All were treated with long term antibiotics (topical, oral and/or intravenous). 8 patients had abnormal initial Gallium scans with mean (± standard deviation) lesion to normal ratio 1.43 ± 0.29. 2 had normal baseline and post treatment Gallium scans but inconclusive bone scans and clinical suspicion necessitated antibiotic therapy. 6 of the 8 patients with abnormal baseline scans had normal post-treatment scans. 2 patients had persistently abnormal scans suggesting residual infection. 1 was lost to follow-up while the other succumbed to end stage liver disease. The mean lesion to normal ratio of normal gallium scans was 1.04 ± 0.08. Gallium uptake was significantly higher on the side of infection compared to the contra lateral side both by visual and quantitative analysis and normalized with infection resolution

Conclusions Gallium SPECT is a promising treatment monitoring tool in temporal bone and skull base osteomyelitis.