Radiology

Nuclear Medicine

What is nuclear medicine?

What is radioactivity?

Radioactivity is the emission of radiation when the nuclei of certain atoms become unstable.

Nuclear medicine is a specialized area of radiology that uses very small amounts of radioactive materials, or radiopharmaceuticals, to examine organ function and structure. Nuclear medicine imaging is a combination of many different disciplines, including chemistry, physics, mathematics, computer technology, and medicine. This branch of radiology is often used to help diagnose and treat abnormalities very early in the progression of a disease, such as thyroid cancer.

Since x-rays pass through soft tissue, such as intestines, muscles, and blood vessels, contrast agents are used in nuclear imaging. Nuclear imaging examines organ function and structure, whereas diagnostic radiology is based on anatomy.

Scans are used to diagnose many medical conditions and diseases. Some of the more common tests include the following:

renal scans - used to examine the kidneys and to detect any abnormalities, such as tumors or obstruction of the renal blood flow.

thyroid scans - used to evaluate thyroid function.

bone scans - used to evaluate any degenerative and/or arthritic changes in the joints, to detect bone diseases and tumors, and/or to determine the cause of bone pain or inflammation.

gallium scans - used to diagnose active infectious and/or inflammatory diseases, tumors, and abscesses.

heart scans - used to identify abnormal blood flow to the heart, to determine the extent of the damage of the heart muscle after a heart attack, and/or to measure heart function.

brain scans - used to investigate problems within the brain and/or in the blood circulation to the brain.

breast scans - often used with mammograms to locate cancerous tissue in the breast.

How are nuclear medicine scans done?

As stated above, nuclear medicine scans may be performed on many organs and tissues of the body. Each type of scan employs certain technology, radiopharmaceuticals, and procedures.

A nuclear medicine scan consists of three phases: tracer (radiopharmaceutical) administration, taking images, and image interpretation. The amount of time between administration of the tracer and the taking of the images may range from a few moments to a few days, depending on the body tissue being examined and the tracer being used. The time required to obtain the images may also vary from minutes to hours.

One of the most commonly performed nuclear medicine examinations is a heart scan. Myocardial perfusion scans and radionuclide angiography scans are the two primary heart scans. In order to give an example of how nuclear medicine scans are done, the process for a heart scan is presented below.

Although each hospital may have specific protocols in place, generally a heart scan may follow this process:

The patient will be asked to undress from the waist up and put on a gown.
The patient is connected to an EKG monitor that records the electrical activity of the heart and monitors the heart during the procedure using small, adhesive, electrode patches.
The patient will lie on a table in the procedure room.
An intravenous (IV) line is started in the hand or arm.
During the procedure, the patient will need to lie as still as possible, as any movement can adversely affect the quality of the scan. The gamma camera (a device to scan patients who have been injected with small amounts of radioactive materials) will be positioned over the patient as he/she lies on the table.
A radioactive tracer will be injected into the IV to "tag" the blood cells so their progress through the patient's heart can be traced with a scanner
The gamma camera obtains images of the heart by measuring the amount of the radioactive substance that has been absorbed by the heart tissue as the patient continues to lie on the table.
The patient may be asked to change positions during the test; however, once the patient has changed position, he/she will need to lie very still.
If the physician wishes to evaluate the heart's function under stress, the patient may exercise on a treadmill or a bicycle for a period of time. Additional images will be obtained after the exercise period.
Once all the heart images have been obtained, the IV will be removed, and the patient will be allowed to leave, unless the physician instructs differently.

This page was last updated on: November 8, 2006.

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