A prospective double-blind comparison of 99mTc-hydroxymethane diphosphonate (HMDP) and 99mTc-methylene diphosphonate (MDP) as bone-seeking agents was performed with 102 patients. Densitometry showed that both cancellous/compact bone and cancellous bone/soft-tissue ratios were greater with HMDP (p less than 0.05); compact bone/soft-tissue and bone lesion/normal bone ratios were the same with both agents. Bone delineation, soft-tissue uptake, and overall image quality were the same with both agents. The HMDP formulation contained 78% fewer stannous ions and had a longer useful life after technetium labeling than MDP.

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Meningioma is one of the neoplasms in which there may be extraosseous localization of bone-seeking radiopharmaceuticals. Tumor calcification, calvarial erosion, and the formation of reactive bone have been proposed as the cause of this abnormal tracer localization. We present a patient with a frontal meningioma that was evaluated using 99mTc-methylene-diphosphonate bone scintigraphy, head computed tomography, and skull radiography; the homogeneous density seen in the radiographic studies corresponded to the area of bone-seeking-agent localization shown in the scintigram. At autopsy, bony tissue and a few psammoma bodies were found in the meningioma, and apparently accounted for the bone-tracer localization. There was no calvarial erosion and no formation of reactive bone. If skull-radiographic studies show a homogeneous, radio-opaque lesion with no reactive changes in the adjacent skull, a meningioma showing a localization of a bone-seeking radiopharmaceutical may be predicted to have bone-tissue formation with or without psammoma bodies.

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