24-Hour/4-hour ratio of technetium-99m methylene diphosphonate uptake in patients with bone metastases and degenerative bone changes.

The uptake of [99mTc]MDP in metastatic lesions of the vertebrae was compared with the uptake in normal vertebrae. The ratio of these lesion-to-nonlesion uptakes at 4 and 24 hr was called the 24-hr/4-hr ratio (TF ratio). A similar ratio was measured for lesions in the spine due to degenerative bone disease. Lesions in vertebrae with degenerative bone disease and treated metastases had a significantly lower TF ratio than lesions in vertebrae with untreated bone metastases. These findings suggest that the TF ratio might be a reliable method for separating metastatic lesions from degenerative changes in the vertebral column, and could be especially useful in cancer patients whose bone scans demonstrate a single lesion in the spine.