Bone scan

Definition

A bone scan is a nuclear medical test used to help diagnose diseases and conditions of the bones.

Purpose

A bone scan is done to provide images of blood flow to the bones. This can help doctors diagnose a variety of diseases and conditions that involve the bones. In general, a bone scan is not enough to determine definitively whether a disease or condition is present, but instead is used in conjunction with a variety of other diagnostic and imaging tests, physical exams, and the individual's health history .

One of the most frequent uses of a bone scan is to determine if cancer occurring in another part of the body has metastized, or spread, to the bones. It can also be used to help diagnose cancers originating in the bones. It can also be used to determine if there is a fracture in a bone when the fracture is not readily visible on an x-ray. Infections of the bones and metabolic disorders of the bones are also diagnosed using bone scans.

Precautions

Bone scans should not be performed on women who are pregnant or nursing. The small amount of radioactive tracer used is not dangerous to adults, however it can be harmful to developing fetuses and

may negatively affect the healthy, normal, development of the baby. Women who are pregnant should either have alternative imaging tests performed or wait to have the procedure until after the baby is born. Women who are currently nursing should also not have a bone scan. The radioactive tracer can be transmitted to the nursing baby through the breast milk. It may be possible for women who are breast feeding to have a bone scan if they stop breastfeeding and do not return to breastfeeding until three or more days after the procedure when the radioactive tracer has been eliminated from the body.

Barium and bismouth can cause the results of the bone scan to be inaccurate. Barium is sometimes used as a contrast material with x rays. If a barium contrast x ray is also required it should be scheduled for after the bone scan. To reduce the chances of inaccurate results a bone scan should not be performed for at least four days after the use of barium. Bismouth can also cause inaccuracies in the scan results. Bismouth is a component of certain prescription and over the counter medications such as Pepto-Bismol. The bone scan should not be done for at least four days after the individual has taken anything containing bismouth.

Description

A bone scan is a nuclear imaging procedure. This means that radioactive material is put into the body and then a camera sensitive to the radiation given off by the material is used to take pictures of it as it moves throughout the body.

The first step of the bone scan is to introduce the radioactive material into the body. A very small amount of radioactive material, called a radionucliotide, radiotracer, or just tracer is injected into the blood stream. It circulates throughout the body in the blood stream and is absorbed into the bones. The tracer gives off very small amounts of gamma radiation. The amount of tracer and radiation given off is too small to be dangerous to adults.

In some cases the doctor may ask that images be taken right after the tracer is injected. In most cases, however, the individual must wait three to four hours for the tracer to circulate throughout the body and be absorbed by the bones. During this waiting time the individual is asked to drink several glasses of water. This helps to flush out any excess tracer that is not taken into the bones.

The patient is asked to urinate right before the scan is done, because any tracer that collects in the bladder can obscure the image of the pelvic area. Any jewelry or metal items must be removed, and the individual is usually given a gown to wear. The individual lays down on a table and must lie completely still as images are taken. The nuclear medicine technician may reposition the individual throughout the scan so that images can be taken of different bones and from different angles.

QUESTIONS TO ASK YOUR DOCTOR

• When can I expect the results of the bone scan?
• If the bone scan shows an abnormality what is the next step?
• What other diagnostic or imaging tests might also help a diagnosis?

The camera used to take images during a bone scan is a gamma camera. It is mounted to an adjustable arm and moves around the patient during the scan. The gamma camera detects gamma radiation, the kind that is given off by the injected tracer. The information about this radiation is then fed into a computer where it is processed into images. In total, the actual scan portion of the bone scan procedure normally takes about one hour.

Preparation

There is no special preparation before a bone scan for most people. Women who are breast feeding may be asked to stop breast feeding before the procedure. The individuals should not take anything containing bismouth, or have any procedures using barium, for at least four days before the scan.

Aftercare

After the bone scan the individual can continue any normal activities. All radioactive material will be flushed from the body within two to three days following the procedure. Women who are breastfeeding should not return to breastfeeding for three or more days to ensure that all radioactive material has been eliminated from their body and will not be inadvertently transferred to the child in the breast milk.

Complications

No complications are expected from a bone scan. However any time an injection occurs there is a small chance of bleeding or infection. In extremely rare cases, an allergic reaction to the injected radioactive substance is possible. In such cases swelling, a rash, or anaphylaxis can occur.

KEY TERMS

oncologist —A doctor who specializes in cancer treatment.

Results

The results of a bone scan do not necessarily indicate what specific disease or condition is present. Instead, the results of the bone scan show if there are any abnormalities in the metabolic action of the bones. A bone scan with normal results show approximately the same amount of radioactive tracer throughout the scan. There are no areas on the scan where there is either no or little tracer shown and there are no areas where a very large amount of tracer is present.

Abnormal bone scan results occur when there are “hot spots” or “cold spots” visible on the scan. “Hot spots” occur when too much of the radioactive tracer accumulates in a certain area. This can indicate a number of problems including a disease that causes the bone to have increased metabolism, bone cancer , a fracture of the bone, an infection of the bone, or a variety of other disease and conditions. “Cold spots” occur when very little of the tracer is present in a certain area of the bones. This can indicate a number of problems including conditions that limit blood flow to the bone, destruction of bone due to tumors, and certain types of bone cancer.

Caregiver concerns

A primary care physician, oncologist, or other doctor orders a bone scan. It is usually performed in the nuclear medicine clinic, lab, or area of a hospital or medical care facility. A nurse injects the individual with the radioactive tracer. A nuclear medicine technician or nuclear medicine technologist operates the gamma camera. The images taken by the gamma camera are interpreted by a radiologist or nuclear medicine specialist.

Resources

BOOKS

Holick, Michael F. and Bess Dawson-Hughes, eds. Nutrition and Bone Health. Totowa, NJ: Humana Press, 2004.

Nelson, Miriam E. Strong Women, Strong Bones: Everything You Need to Know to Prevent, Treat, and Beat Osteoporosis. New York, NY: Perigee Book, 2006.

Qin, L. et al, eds. Advanced Bioimaging Technologies in Assessment of the Quality of Bone and Scaffold Materials: Techniques and Applications. Berlin: New York Springer, 2007.

PERIODICALS

“Bone Scan.” Health A-to-Z (August 21, 2006).

Gould, Paula. “Whole-body MR Imaging Outclasses Bone Scans—Head-to-Toe Scanning in Multiple Planes Detects Bony Metastases and Soft Tissue Involvement.” Diagnostic Imaging 28.15 (April 1, 2007): 15.

ORGANIZATIONS

Center for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30333, 800-CDC-INFO, http://www.ahima.org/.

Robert Bockstiegel