This image is taken from a bone scan of patient with breast cancer who complained of weight loss, lethargy
and generalised bone pain. It show multiple metastases within both the axial and peripheral skeleton. Increased
uptake of the isotope is seen in the ribs, scapulae, pelvis and skull. Renal excretion of the isotope has
highlighted both the kidneys and bladder.
Bone scintigraphy is performed using technitium-99m labeled substituted diphosphonates. Following intravenous
injection, the isotope is cleared from the blood stream into the skeleton with a high extraction efficiency.
Over 50% of the injected dose is taken up by the skeleton by three hours. The two factors that determine isotope
uptake are blood flow and osteoblastic activity. In order to produce the most satisfactory images 400 - 600 MBq
of isotope are used and the images are obtained between 2 and 4 hours post-injection. A full body scan
takes approximately 20 minutes. The total body radiation dose is roughly 5mSv which is a similar does to that
received from an IVU or lumbar spine series.
In the investigation of potential bone lesions plain X-rays should be the initial investigation. However, the
sensitivity of plain films are limited and there is often a prolonged lag period between the onset of a
pathological process and any radiological changes. This can range from days in infective processes (e.g.
osteomyelitis) to weeks or months in neoplastic disease (e.g. bone metastases). Bone scintigraphy is the most
sensitive imaging modality for the recognition of bone disease. It is useful in the detection of disease,
assessing the extent of the process and estimating the function of any lesion that is identified. It is
particularly useful in the 'screening' of patients for bone metastases and in detecting bone lesions in
symptomatic patients with normal radiological findings.
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