Background
A bone scan,
or bone scintigraphy, is a
diagnostic nuclear scanning test to find bone abnormalities, including bone
cancer or cancer that has metastasized to bone, inflammation, fractures not
discernible on traditional x-rays, and damage owing to infections and other
problems. A radioactive agent is administered intravenously and absorbed
radioactivity is detected by measuring the interaction between gamma rays
emitted by the body and sodium iodide crystals located in the scintillation
camera. One advantage of skeletal scintigraphy over other diagnostic modalities
is the ability to view the entire skeleton in one image. The image provides a
“metabolic picture” that identifies the location of a lesion or injury by
comparing its metabolic activity versus adjacent, normal bone.1
Description
The patient received an intravenous injection of radioactive
material (eg, technetium-99m-MDP) and is then scanned with a gamma camera, which
is sensitive to the radiation emitted by the injected material. About half of
the radioactive material is localized by the bones. The more active the bone
turnover, the more radioactive material will be seen. Evaluation for osteomyelitis
or fracture requires a Triphasic Bone Scan. During the first and second phases,
images are taken during the initial injection. For the third phase, images are
taken 2–3 hours later. The three phase bone scan detects different types of
pathology in the bone: the first phase images typically show perfusion to a
lesion, second phase images show blood flow to the area, and third phase images
best show the extent of bone turnover associated with a lesion. Some tumors, fractures
and infections show up as areas of increased uptake. Others can cause decreased
uptake of radioactive material.
