RADIOPHARMACEUTICALS

Radionuclide bone imaging is performed with phosphate compounds which are labeled to 99m-Technetium.

Living bone is a very dynamic organ. There is always osteoclastic and osteoblastic activity occuring. The radiopharmaceutical used for bone imaging is a phosphate compound attached to 99-m technetium. This phosphate compound is chemadsorbed to the hydroxy apatite crystal during ossification which occurs during new bone formation. Since there is continual turnover of bone normally, by two to three hours post-injection a significant amount will be found in normal bone. Areas where there is increased bone turnover, which can occur as a reaction to any process of bone invasion or destruction will demonstrate increased activity, or a "hot"spot".

The radionuclide is injected intravenously. There is a three hour waiting period to allow for maximaum concentration of activity in the bones. The material which is not localized in the bony skeletan is excreted by the kidneys and is eliminated in the urine. It is therefore, important that all patients referred for bone scanning be well hydrated to improve the quality of images and decrease the radiation dose.