Imaging of bone metastases in prostate cancer: an update.

Assessing bone metastases is often beyond the scope of plain - film radiography, and nuclear imaging in particular with bone scintigraphy has proved the mainstay for detection of bony disease for over 40 years. Bone scanning with 99mTechnetium - labeled diphosphonates relies on the detection of pathological osteoblastic response elicited from malignant cells. This technique offers the advantage of whole body examination, low cost, availability and high sensitivity. However, it suffers from relative low specificity. The addition of single-photon emission computed tomography (SPECT) to bone scintigraphy has markedly improved the diagnostic benefit. Although the accuracy of SPECT is significantly higher than that of planar scintigraphy, there is still room for improvement of anatomic localization and morphological characterization, a limitation that has currently been mainly overcome with the upcoming of combined SPECT-CT (computed tomography). Positron emission tomography (PET), a modality with higher spatial resolution than that of SPECT can be particularly helpful in detecting small lesions. Moreover, PET imaging using various specific radiotracers has the advantage of detecting malignant disease in both bone and soft tissues. It is highly sensitive mainly in detecting early bone marrow as well as for diagnosing lytic bony metastases and can be also reliably used to monitor therapy response. In this review, we present the current role of SPECT and PET in the imaging of skeletal metastases from prostate cancer.