General Nuclear Medicine
What is General Nuclear Medicine?
Nuclear medicine is a subspecialty within the field of radiology. It comprises
diagnostic examinations that result in images of body anatomy and function.
The images are developed based on the detection of energy emitted from
a radioactive substance given to the patient, either intravenously or by
mouth. Generally, radiation to the patient is similar to that resulting
from standard x-ray examinations.
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What are some common uses of the procedure?
Nuclear medicine images can assist the physician in diagnosing diseases.
Tumors, infection and other disorders can be detected by evaluating organ
function. Specifically, nuclear medicine can be used to:
- Analyze kidney function
- Image blood flow and function of the heart
- Scan lungs for respiratory and blood-flow problems
- Identify blockage of the gallbladder
- Evaluate bones for fracture, infection, arthritis or tumor
- Determine the presence or spread of cancer
- Identify bleeding into the bowel
- Locate the presence of infection
- Measure thyroid function to detect an overactive or underactive
thyroid
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How should I prepare for the procedure?
Usually, no special preparation is needed for a nuclear medicine examination.
However, if the procedure involves evaluation of the stomach, you may have
to skip the meal immediately before the test. If the procedure involves
evaluation of the kidneys, you may need to drink plenty of water before
the test.
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What does the equipment look like?
During most nuclear medicine examinations, you will lie down on a scanning
table. Consequently, the only piece of equipment you may notice is the
specialized nuclear imaging camera used during the procedure. It is enclosed
in metallic housing designed to facilitate imaging of specific parts of
the body. It can look like a large round metallic apparatus suspended from
a tall, moveable post or a sleek one-piece metal arm that hangs over the
examination table. The camera can also be within a large, doughnut-shaped
structure similar in appearance to a computed tomography (CT) scanner.
Sometimes, the camera is beneath the table out of view.
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How does the procedure work?
You are given a small dose of radioactive material, usually intravenously
but sometimes orally, that localizes in specific body organ systems. This
compound, called a radiopharmaceutical or tracer, eventually collects in
the organ and gives off energy as gamma rays. The gamma camera detects
the rays and works with a computer to produce images and measurements of
organs and tissues.
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How is the procedure performed?
A radiopharmaceutical is usually administered into a vein. Depending on
which type of scan is being performed, the imaging will be done either
immediately, a few hours later, or even several days after the injection.
Imaging time varies, generally ranging from 20 to 45 minutes.
The radiopharmaceutical that is used is determined by what part of the body
is under study since some compounds collect in specific organs better than
others. Depending on the type of scan, it may take several seconds to several
days for the substance to travel through the body and accumulate in the
organ under study, thus the wide range in scanning times.
While the images are being obtained, you must remain as still as possible.
This is especially true when a series of images are obtained to show how
an organ functions over time.
After the procedure, a physician with specialized training in nuclear medicine
checks the quality of the images to ensure that an optimal diagnostic study
has been performed.
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What will I experience during the procedure?
Some minor discomfort during a nuclear medicine procedure may arise from
the intravenous injection, usually done with a small needle. With some
special studies, a catheter may be placed into the bladder, which may cause
temporary discomfort. Lying still on the examining table may be uncomfortable
for some patients.
Most of the radioactivity passes out of your body in urine or stool. The
rest simply disappears through natural loss of radioactivity over time.
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Who interprets the results and how do I get them?
Most patients undergo a nuclear medicine examination because their primary
care physician has recommended it. A physician who has specialized training
in nuclear medicine will interpret the images and forward a report to your
physician. It usually takes a day or so to interpret, report and deliver
the results.
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What are the benefits vs. risks?
Benefits
- The functional information provided by nuclear medicine examinations
is unique and currently unattainable by using other imaging procedures.
For many diseases, nuclear medicine studies yield the most useful
information needed to make a diagnosis and to determine appropriate treatment,
if any.
- Nuclear medicine is much less traumatic than exploratory surgery, and
allergic reaction to the radiopharmaceutical material is extremely
rare.
Risks
- Because the doses of radiopharmaceutical administered are very small,
nuclear medicine procedures result in exposure to a small dose
of radiation. Nuclear medicine has been used for more than five decades,
and there are no known long-term adverse effects from such low-dose studies.
- As with all radiologic procedures, be sure to inform your physician
if you are pregnant. In general, exposure to radiation during pregnancy
should be kept to a minimum.
- Allergic reactions to the radiopharmaceutical can occur, but are extremely
rare.
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What are the limitations of General Nuclear Medicine?
Nuclear medicine procedures are time-consuming. They involve administration
of a radiopharmaceutical, obtaining images, and interpreting the results.
It can take hours to days for the radiopharmaceutical to accumulate in
the part of the body under study. Imaging can take up to three hours to
perform, though new equipment is available that can substantially shorten
the procedure time.
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