scintigraphy is one of the most frequently performed of all radionuclide
procedures. The procedure is performed with technetium-99m– labelled diphosphonates,
which accumulate in the bones. The degree of radiotracer uptake in the bones depends
primarily on two factors: blood flow and, perhaps more importantly, the rate of
new bone formation
The normal scintigraphic findings on bone scan show
symmetric distribution of activity
throughout the skeletal system in healthy adults. Urinary bladder activity,
faint renal activity, and minimal soft-tissue activity are also normally
A bone scan is extremely sensitive tool for detecting osteoblastic metastasis and is therefore used as part of the routine staging for patient with breast, prostate and lung cancer. The usual pattern
consists of increased radiotracer deposition in areas of osteoblastic
reparative activity in response to tumor osteolysis. The presence of multiple,
randomly distributed areas of increased uptake of varying size, shape, and
intensity is highly suggestive of bone metastases.
When the metastatic process is diffuse,
virtually all of the radiotracer is concentrated in the skeleton, with little
or no activity in the soft tissues or urinary tract. The resulting pattern,
which is characterized by excellent bone detail, is frequently referred to as a
superscan. A superscan may also be associated with metabolic bone disease.
Unlike in metastatic disease, however, the uptake in metabolic bone disease is
more uniform in appearance and extends into the distal appendicular skeleton.
Intense calvarial uptake that is disproportionate to that in the remainder of
the skeleton is another feature of a metabolic superscan.