Bone Radionuclide Scan

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Bone radionuclide scan

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.

Preparation

Some specialized blood studies should be drawn before this study is performed. Jewelry or metallic objects need to be removed. No other special physical preparation is required. The patient should understand that there is no danger of any significant radioactive exposure to themselves or others, as only small amounts of the radioisotope are used. The total dose of radiation absorbed is minimal, often less than the amount received from ordinary x rays. The radionuclide scanner does not emit any radiation at all, but detects and records it from the patient.

Aftercare

Fluids are encouraged after the scan to aid in the excretion of the radionuclide. It is almost completely eliminated from the body within 24 hours.

Complications

There are no complications associated with this test.

Results

The normal appearance of the scan will vary according to the patient's age. In general, a uniform concentration of radionuclide uptake is present in all bones in a normal scan. A high concentration of radionuclide occurs in areas of increased bone metabolism . These regions appear brighter and may be referred to as "hot spots." They may indicate healing fractures, tumors, infections, inflammations, or other processes which trigger new bone formation. Lower concentrations of radionuclide may be called "cold spots." Poor blood flow to an area of bone, or bone destruction from tumor may produce a cold spot. The bone scan is a very sensitive test and can detect subtle conditions more readily than other studies. However, it is not a very specific examination, and often cannot distinguish exactly what disease process is causing an abnormality. Results need to be correlated with the patient's medical history, and other radiologic and laboratory studies to make a definite diagnosis.

Health care team roles

Bone scans are performed by a nuclear medicine technologist. In most facilities, the nuclear medicine technologist is a trained individual with certification. The technologist administers the radioactive material, obtains pertinent medical history from the patient, and instructs the patient about the procedure. The data collected is interpreted by a doctor who is a radiologist or nuclear medicine specialist and the results of the bone scan are obtained from the referring physician. Since there is no preparation for this test the services of other medical personnel are generally not required.