A nuclear medicine procedure is sometimes described as an "inside-out" x-ray
because it records radiation emitting from the patient's body rather than
radiation that is directed through the patient's body. Nuclear medicine
procedures use small amounts of radioactive materials, called
radiopharmaceuticals, to create images of anatomy. Radiopharmaceuticals are
substances that are attracted to specific organs, bones or tissues. They are
introduced into the patient's body by injection, swallowing or inhalation. As
the radiopharmaceutical travels through the body, it produces radioactive
emissions. A special type of camera detects these emissions in the organ, bone
or tissue being imaged and then records the information on a computer screen or
Nuclear medicine is unique because it documents function as well as
structure. For example, nuclear medicine allows physicians to see how a kidney
is functioning, not just what it looks like. Most other diagnostic imaging
tests, in comparison, reveal only structure. Nuclear medicine procedures are
performed to assess the function of nearly every organ. Common nuclear medicine
procedures include thyroid studies, brain scans, bone scans, lung scans, cardiac
stress tests, and liver and gallbladder procedures.
Although nuclear medicine is primarily used for diagnosis, it can be used to
treat disease as well. Therapeutic uses include treatment of hyperthyroidism and
pain relief from certain types of bone cancers.
There are more than 100 different nuclear medicine examinations. This page
offers a general introduction to six of the most common tests. For more detailed
information, visit the Society of Nuclear Medicine's Web site at
Before your examination, a nuclear medicine technologist will explain the
procedure to you and answer any questions you might have. A nuclear medicine
technologist is a skilled medical professional who has received specialized
education in the areas of anatomy, radiation protection, patient care, radiation
exposure, radiopharmaceuticals and nuclear medicine procedures.
Tell the technologist if you have any allergies and if you are undergoing
radiation therapy, because these factors may require adjustments in how the
examination is performed. Also, be sure to tell the technologist if you are
pregnant or are breastfeeding. Nuclear medicine tests usually are not
recommended for pregnant women.
During the Examination
For most nuclear medicine examinations, the patient is positioned on a
scanning table underneath a scintillation or gamma camera. A radiopharmaceutical
then is administered intravenously, orally or through inhalation. It travels
through the patient's bloodstream to a specific area where it selectively
accumulates. The camera then detects and records the radioactive emissions from
the patient's body.
For some nuclear medicine studies, imaging takes place immediately. For
others, images are taken an hour, two hours, or even several days after
administration of the radiopharmaceutical. In most cases, the patient is
permitted to leave the hospital and return later for the imaging procedure.
Most nuclear medicine procedures require several different images from
different angles, and the technologist may ask you to change positions during
the examination. You will need to lie still during each scan.
During a nuclear medicine brain scan, images are taken of the front, back,
sides and sometimes top of the head. Scans usually are taken 30 to 60 minutes
following the injection of a radiopharmaceutical, although some tests require
the patient to return a day or two later for scanning. It's important that you
not move, cough or touch your head while the scans are being taken. Brain scans
are used to diagnose strokes, tumors and infections of the brain. A study of
blood circulation in the brain is called a cerebral perfusion scan.
A thyroid uptake study shows how well the thyroid gland is functioning. If
the radiopharmaceutical is administered orally, you will be asked to return the
next day for scanning. If it is injected, the scans are performed immediately.
You may be asked to avoid all foods and medicines that contain iodine for
several days before the test, because they can distort the test results.
Lung scans usually are performed to detect blood clots in the lungs. Often, a
chest x-ray is taken in conjunction with the lung scan. The x-ray image and the
nuclear medicine image are compared to help your physician better identify a
For most types of cardiac imaging, scans are taken two to four hours after
the radiopharmaceutical is administered. For a cardiac stress-rest test, you
probably will be asked not to eat three to four hours before the test because
the images of your heart will be easier to interpret if your stomach is empty.
During the test, you will be asked to perform mild exercise, such as walking on
a treadmill or riding a stationary bicycle, while a radiopharmaceutical is
administered. An electrocardiogram will monitor your heart rhythm while you
exercise. Nuclear medicine scans will be taken immediately and then repeated
several hours later. This study reveals blood flow to the heart to help detect
coronary artery disease.
For gallbladder imaging, images usually are taken within an hour of
administration of a radiopharmaceutical. You may be asked to return several
hours later for additional images. The study can detect gallbladder disease and
reveal how well the liver is functioning.
Bone scans can detect fractures, tumors and infections. Imaging may be
performed immediately, although it usually is performed several hours after the
radiopharmaceutical is injected. If your entire body needs to be scanned, the
imaging portion of the procedure can last two to four hours. If you have trouble
lying on your back for extended periods of time, be sure to let your physician
know. Radiographs also may be taken to provide additional information.
About PET and SPECT
You may hear the terms "PET" and "SPECT" used in conjunction with nuclear
medicine procedures. Positron emission tomography, or PET, uses a special camera
and computer to construct a 3-D image of the area being scanned. PET is
increasingly and transforming them into visual data.
After the examination, your nuclear medicine scans will be reviewed by a
radiologist, a physician who specializes in the interpretation of diagnostic
medical images. Your personal physician will receive a report of the
radiologist's findings. Your physician then will advise you of the results and
discuss what further procedures, if any, are needed.
The radiation that you are exposed to during a nuclear medicine procedure is
equal to or less than a standard x-ray or CT scan covering the same body area.
In general, the radiopharmaceutical administered during the examination will be
eliminated naturally from your body in one or two days. Drinking fluids will
help clear the radiopharmaceutical from your system more quickly. You do not
need to avoid contact with other people during this time, although your
physician may recommend simple acts, such as flushing the toilet twice after
using it, to reduce the small chance of radiation exposure to others in your
The above patient information provided by the American Society of Radiologic
Technologist (ASRT) with permission. www.asrt.org