Radionuclide bone SPECT/CT in orthopaedics

Radionuclide 99mTc-MDP planar bone scan is the most commonly performed nuclear medicine procedure and may aid diagnosis of benign and malignant bone pathologies. 99mTc-MDP is injected intravenously and subsequently taken up by osteoblasts and incorporated into the bone matrix. In the process it acts as a marker for new bone formation, bone turnover and local vascularity. The high sensitivity of the 99mTc-MDP bone scan for detection of skeletal metastases and the ability to image the entire skeleton has maintained its role in oncology imaging in combination with other imaging modalities. In contrast, the main limitation of planar 99mTc-MDP bone scan is its limited specificity. It can be a challenge with planar bone scans to accurately localise lesions due to overlying structures, and also to fully characterise the abnormality accurately on a single imaging modality. With the emergence of hybrid imaging such as SPECT/CT and PET/CT it is possible to obtain and provide both morphological/anatomical and metabolic/functional data concurrently. SPECT/CT can harness the improved spatial resolution of SPECT and co-registration with CT to enable accurate localisation and the diagnostic features from the two tests can be used together to improve the diagnostic potential. There is a developing body of evidence that supports the use of 99m-Tc MDP SPECT/CT routinely in orthopaedics. In this article the authors share their experience, review the contemporary literature and summarise the role of SPECT/CT in orthopaedics.