Quantitative Bone Single Photon Emission Computed Tomography/Computed Tomography for Evaluating Response to Bisphosphonate Treatment in Patients with Paget's Disease of Bone

We here report on 2 cases of monostotic Paget's disease of bone, one in the ilium and the other in the skull, including quantitative values obtained with bone single photon emission computed tomography/computed tomography (SPECT/CT), which were useful to evaluate the response to bisphosphonate treatment. The quantitative parameters determined with those findings were decreased, with the maximum standardized uptake value (SUV), peak SUV, mean SUV, metabolic bone volume, and total bone uptake in case 1 and case 2 reduced by 48.8 and 60.3%, 46.6 and 58.8%, 24.3 and 60.5%, 87.0 and 11.8%, and 90.2 and 55.8%, respectively, while TRACP-5B and alkaline phosphatase (ALP) were also reduced by 39.5 and 88.6% and by 53.7 and 78.1%, respectively. Quantitative SPECT/CT parameter decreases were correlated with TRACP-5B and ALP, indicating the usefulness of this modality to examine treatment response.