Bone Radionuclide Scan Health Article

Definition

A bone scan is a diagnostic imaging procedure used to evaluate abnormalities involving bones and joints. A radionuclide is injected intravenously, and its distribution in the skeletal system is analyzed to detect certain diseases or conditions.

Purpose

Bone scans are performed to evaluate metastases, trauma, arthritis, metabolic diseases, bone marrow hyperplasia, and Paget's disease. Bone scans are most frequently ordered to investigate the cause of bone pain or to check whether a cancer originating in another organ has spread to the bones. For example, certain cancers, such as breast and prostate, are most likely to spread, or metastasize, to the bones. If metastases are found, periodic bone scans may be ordered to determine if therapeutic treatment has been effective.

If there is a suspected fracture that is not revealed on x ray, a bone scan is performed to confirm the suspicion of a fracture. When an abnormality is found on an x ray of a bone, a bone scan may be helpful in determining the nature of the abnormality. Infection in the bone (osteomyelitis) can be detected or confirmed by a bone scan, often days or weeks before an x ray would reveal it. Bone scans are useful in diagnosing early arthritic changes, and monitoring both the progression of the disease and the effectiveness of treatment. Unexplained pain may be evaluated with a bone scan, because it can demonstrate fractures which are difficult to detect on x ray. Bone scans can be used to see if artificial joints have loosened or become infected. Suspected child abuse may be evaluated with a bone scan, due to its ability to see an overall pattern of repeated trauma. Abnormalities caused by altered circulation to the bone may be diagnosed with a bone scan.

Precautions

The use of a radioactive substance is required to perform a bone scan, and therefore women who are pregnant should not have this test unless her physician indicates that the benefit will outweigh the risks. If a woman is breastfeeding, she will be advised to stop for a specified period of time, usually for one day, depending on the dose. A patient who is unable to remain still for an extended period of time may require light sedation for a bone scan.

Description

This test is performed in a radiology or a nuclear medicine facility, either in a hospital department or an outpatient x-ray center. The patient usually sits or lies down while a radioactive substance is injected through a vein in the arm. For a bone scan, the radionuclide used is specifically chosen because it accumulates in bone tissue. The patient then waits from three to four hours for the substance to collect within the skeletal system. Excess radionuclide is excreted through the urinary system and it is customary that, during the waiting time, the patient will be asked to drink several glasses of water. Patients are free to get up and move around as they desire during the waiting time. Just before the scanning begins, the patient will be asked to empty their bladder so that pelvic bones will not be obscured by residual radioactivity collected in the bladder. During the scan, the patient lies on his or her back on a table, but may be repositioned onto the stomach or side during the study. It is important for the patient not to move, except when directed by the technologist.

The radionuclide scanner, sometimes called a gamma camera, or scintillation camera, is positioned against the body part to be examined. Either the camera, the table, or both, may change position during the study. For a total body bone scan, the patient is scanned from head to foot, over a period of 30 to 60 minutes. Images are obtained both anteriorly and posteriorly and occasionally, a lateral image may be obtained. Patients should experience no discomfort from this examination. A special kind of bone scan, called a SPECT (Single Photon Emission Computed Tomography) scan may be added, to study a particular part of the body in more detail. Suspected diseases of the hips, lower back, or jaw are often evaluated using this study. It usually takes an additional 30 to 45 minutes. The camera circles completely around the area in question and helps pinpoint the location of the abnormality being evaluated.

Another variation is called a triple-phase, or three-stage, bone scan, which demonstrates blood flow to the bones. The procedure is the same, except the scanning takes place immediately after the radioactive substance is injected for approximately 20 minutes after the injection, and then again two to four hours later.