A bone scan for cancer involves injecting a radioactive substance called a tracer into a vein to produce gamma waves that can be picked up by a special camera. The tracer consists of radionuclides that bind to the bone and show up as dark or light spots in a bone scan for cancer. This procedure uses nuclear technology to detect bone cancer or cancer that has metastasized to the bone from another part of the body.
Patients preparing for a bone scan for cancer do not need to fast before the test. A technician typically injects the tracer, which might feel like a bee sting. It usually takes between one and four hours for the radioactive substance to move throughout the skeleton. During this time, patients will be asked to drink up to six glasses of water to flush any tracer material not absorbed by bone.
The actual bone scan for cancer might last up to an hour, if the entire body is examined. Patients must remain still on a padded table while a large camera passes over the body. Movement during the actual scan might produce blurred images. Although, the procedure is painless, some patients find it difficult to lie still during a bone scan for cancer, especially if they experience bone pain.
A radiologist or specialist in nuclear medicine looks for dark or light areas picked up by the camera. A dark spot, also called a cold spot, might indicate decreased blood supply and lack of absorption of the tracer. Cold spots might also mean cancer is present in the bone as a primary diagnosis or cancer spreading to the bone from an organ. A normal scan shows evenly distributed tracer throughout the body.
Light spots on images, also referred to as hot spots, represent excessive binding of the tracer to the surface of the bone. This might indicate arthritis, a fracture, or bone infection. In addition to using a bone scan for cancer, physicians use the procedure to study bone pain without a known cause, and to treat leukemia and lymphoma patients.
Other tests might be used in conjunction with a bone scan for cancer to rule out the disease. Single-photon emission computerized tomography (SPECT) can produce images of deep layers in the bone, a process that takes about 30 minutes. Doctors might also order a magnetic resonance imaging test or bone biopsy to detect bone cancer.
Risks associated with a bone scan are considered low, with about the same level of radiation exposure as a common X-ray. Radionuclides injected into the bloodstream are excreted through the urine and completely gone within a couple of days. An allergic reaction to the tracer material rarely occurs, but is possible.