Bone Scan Test
Bone Scan Test
A bone scan test, also known as radionuclide imaging or bone scintigraphy, is a medical imaging test that is designed to detect bone abnormalities such as fractures, tumors, and cancer. A bone scan results in a 2-d, black and white image of the entire human skeleton. This black and white image, which may be seen on a film image or on a computer screen, highlights areas of abnormal bone activity as darker spots on the image. These darker spots on the images are also known as "hot" spots. In these hot spots, there is increased cellular activity in the osteoblasts - the cells responsible for making new bone. These osteoblasts produce new bone material to replace the bone material that has been lost, due to fractures, bone pain, or bone loss.
The bone scan is a two part test. In the first part of the test, a patient is injected with a radioactive substance called MBq of technetium-99m-MDP. The second part of the test involves the photography of the entire human skeleton, done with a gamma camera. The scan takes place a few hours following the injection. While the patient is waiting, the injected radionucleotide courses through the human body, and is absorbed by the bones. More of this radionucleotide will be absorbed by the bones tissues in which there is increased cellular activity in the osteoblasts of the bones.
How do doctors interpret the results of bone scans? Bone scans do provide doctors with a great deal of diagnostic information, though they usually won't tell doctors what is specifically wrong with the sections of the bones where there are hot spots. From the bone scans, we do know that some type of traumatic event has occurred in the sections of bones that show up darker on the image. That part of the bone has been damaged for some reason, and the body has responded to that injury by increasing the activity of the osteoblast cells. Bone remodeling results due to this osteoblast activity, and the part of the bone that has been compromised will be replaced by strong, healthy bone. But from this scan alone, we may not know what caused the bone damaged. Possible causes for the bone damage that may result in hot spots include cancer of the bone, bone tumors, infections, fractures, and arthritis.
Bone scans that are positive for dark spots may result in additional tests, including blood testing, CT Scans, MRIs, and FDG-PET (Positron emission tomography) scan.
Why do doctors order bone scans? Doctors may order bone scans if they believe that infections, cancer, or tumors are the undiagnosed cause of back pain. This test may be especially important for patients who have had a recent infection or have a history of metastatic cancer. The cancer or infection may have spread from one area of the body to the bones. Another reason that this test may be ordered is if spine fractures are suspected but were not present on recent X-rays of the spine. Some small fractures may show as negative results on X-rays, but produce dark spots on a bone scan test.
Technique/procedure: The bone involves the injection of a small amount of radioactive material; and the follow-up imaging takes place two to three hours later. The radioactive material is absorbed through the bones. The follow-up scan involves a patient lying still, on their stomach, while the gamma camera produced an image based on the amount of nuclear material that is absorbed in each section of bone. Patients shouldn't feel any pain related to the injected radioactive substance or the imaging from the camera. Patients may experience discomfort related to having to lay on a hard surface for an hour while remaining motionless. Patients only sustain a small amount of radiation exposure related to the scan - 0.15 rad.
Patients may perform a test known as a single photon emission computed tomography (SPECT) imaging if they want to zero in on a small area of hot spots discovered in this test. SPECT imaging involves providing doctors with a more 3d picture of lesions of bone that are 1cm or less.
Our bones in the body go through a process called bone remodeling, or bone turnover, in response to their injuries. Bone remodeling is a process by which the bones replace injured bone tissue with new, healthy bone.