Single-Photon Emission Computed Tomography
FAQ
What is General Nuclear
Medicine?
 Nuclear
medicine is a subspecialty within 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. Radiation to the patient
is, generally, similar to that resulting from standard x-ray
examinations.
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
(cystic duct)
-
Evaluate bones for fracture,
infection, arthritis or tumor
-
Determine the presence or spread of
cancer
-
Locate the presence of infection
-
Measure thyroid uptake to detect
hyperthyroidism or hypothyroidism
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.
 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 gamma 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. Often, the camera is beneath
the table out of view.
A nearby computer console, possibly in
another room, processes the data from the procedure.
How does the procedure work?
You are given a compound, usually
intravenously but sometimes orally, containing a small amount of a
radioactive substance 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.
How is the procedure performed?
A radiopharmaceutical is administered
into a vein. Depending on which type of scan is being performed, the
imaging will be done either immediately or a few hours or even two
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.
You must remain as still as possible
during imaging. If the gamma camera is moved slowly along the body,
the resulting image is called a planar scan. Sometimes sequential
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.
What will I experience during the
procedure?
Some 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 unpleasant for some
patients.
The radiopharmaceutical loses its
radioactivity generally over 24 hours. It passes out of the body in
the urine or stool.
Who interprets the results and how do
I get them?
Most patients undergo a nuclear medicine
examination because a referring physician has recommended it. A
physician who has specialized training in nuclear medicine will
interpret the images and forward a report to the referring
physician. It usually takes one to three days to interpret, report
and deliver the results.
What are the benefits vs. risks?
-
Nuclear medicine is much less
traumatic than exploratory surgery.
-
Nuclear Medicine procedures will
result in exposure to a small dose of radiation. However, the
doses of radiopharmaceutical administered are the smallest
possible. Nuclear medicine has been used for more than three
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.
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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