Nuclear medicine modalities to image bone metastases with bone-targeting agents: Conventional scintigraphy and positron-emission tomography

Abstract

99mTc-MDP whole-body bone scintigraphy is a sensitive, an available, and a relatively low-cost modality which is utilized for the evaluation of skeletal metastases from prostate cancer, in response to treatment and patient’s prognosis, using the bone scan index. However, due to tracer uptake by benign bone lesions such as inflammatory, degenerative, and traumatic changes, the method is not highly specific. To mitigate this shortcoming, the planar imaging is complemented with SPECT to better detect and localize the lesions. Also, application of hybrid SPECT/CT scan may provide both anatomic and functional data in a single study and more accurately differentiate metastatic from benign lesions. The other technique that has been increasingly used during the last decade is 18F-NaF PET/CT. It provides better sensitivity, specificity, and spatial resolution as well as monitoring the response to treatment when compared with conventional bone scan. Furthermore, 18F-NaF PET/CT exhibits the occult metastases more accurately in lower PSA level. Recently, the combination of 18F-NaF with other specific PET tracers (e.g., 18F-choline) in a single PET/CT (i.e., dual tracer PET/CT) is introduced as a promising imaging technique in the evaluation of prostate cancer patients which allows more accurate assessment of both skeletal and soft tissue malignancies. In summary, we believe that based on increasing number of established PET/CT scanners and decreasing price for PET radiotracers, as well as better accuracy in detecting metastatic lesions, 18F-NaF PET/CT will supplant conventional 99mTc-MDP whole-body bone scintigraphy in the near future for evaluation of skeletal metastatic disease from prostate cancer.