A delicate balance exists in keeping the bones of the body healthy and strong. Abnormalities in this delicate balance can lead to many diseases and conditions that must be treated promptly to avoid further complications. Imaging tests, such as a bone scan, allow physicians to examine and diagnose bone abnormalities in a safe and effective manner.
Bone Metabolism
Bone metabolism refers to the process by which old bones are broken down and new bone is formed. It is a dynamic, ongoing process that keeps bones healthy and strong. Certain conditions or the aging process can disrupt the balance of the process, causing bone to be removed faster than new bone is added, or vice versa. This can impair the structural integrity of bones, leading to many bone diseases. The theory behind a bone scan is to detect imbalances in bone metabolism to diagnose or monitor these conditions, even before symptoms have manifested.
Why Is It Done?
A bone scan is a nuclear imaging test performed to detect any abnormalities in the bone metabolism process. It is helpful in identifying fractures, arthritis, Paget's disease and infections of the bone. For unexplained bone pain, a bone scan can help in determining the location and possible cause of the pain. In cancer therapy, a bone scan can be used to diagnose cancer of the bone or to detect cancer that has spread to the bone from another area of the body, such as the lungs or breast. Along with diagnosing, bone scans are used to monitor the progression and treatment outcomes of bone disorders such as osteoporosis, according to Medline Plus.
Procedure
A bone scan begins with the injection of small, radioactive tracers into the body through a vein in the arm. Individuals must wait two to four hours for the tracers to circulate the body and be absorbed, before scanning can begin. The tracers are absorbed by body tissues, particularly bone, and emit small amounts of radiation called gamma rays that are detected by a special camera on the bone scan machine. During the wait, it is advised to drink plenty of water to eliminate any excess radioactive substance in the body, according to Medline Plus. For the scanning and image production process, individuals must lie still on a table while a camera slowly passes over the body taking pictures and detecting the emitted gamma rays. The scanning process is painless and can take up to an hour if it is a full body scan. A radiologist will then examine the results to determine a diagnosis.
Results
A bone scan test is evaluated by a radiologist who looks for abnormal color distributions of the resulting gamma detection images. With healthy bone undergoing normal turnover, the radioactive tracers will distribute evenly throughout the bones. However, if bone metabolism has been disrupted, "hot" or "cold" spots will appear, indicating a problem. "Hot spots" are dark spots on the bone image that indicate increased turnover of bone where more of the radioactive tracer had been absorbed. "Cold spots" appear much lighter because fewer tracers had been absorbed by the bone, indicating decreased bone turnover, according to Medline Plus.
Risk
A bone scan is a safe and relatively painless imaging procedure. The scanning process is completely painless, but minor pain may be experienced when injecting the radioactive tracer substance. An allergic reaction to the injected substance, resulting in a rash, itchiness and swelling, may occur but is rare, according to the Mayo Clinic. Radiation exposure has been linked to cancer, but the amount of radiation exposure during a bone scan is minimal and is no more harmful than a typical X-ray, according to the Mayo Clinic.
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