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Frequently Asked Questions
Nuclear Medicine
Bone Scan . Lung Scan . Cardiac Scanning . Equipment & Images
Unlike x-ray examinations, studies in nuclear medicine are performed by administering
slightly radioactive materials to a patient and then imaging with a camera that detects
the emissions. The camera does not give off radiation.
Although most studies involve
the intravenous injection of the material, some studies use an injection in the skin or
spinal canal. There are even examinations that have a radioactive label in food that is then eaten. The material administered in these tests localizes within the patient and is used to measure the
function of a particular organ system. In many instances, observing the changes in the
function of an organ is a very sensitive way to detect a disease process.
In general,
nuclear medicine studies provide a low dose of radiation and side effects and allergies
to the materials are extremely rare.
Nuclear bone scans
A bone scan is a test that measures the rate of formation of bone and creates a
picture of the skeleton based upon this. Virtually any disease that causes injury to bone
will also cause new bone to form. This change in the normal turnover of bone is a very
sensitive measure of many disease processes.
Bone scans are frequently utilized to
detect the spread of tumor to bones, especially from cancer of the prostate or the
breast. These studies are also often used for looking for fractures and sites of bone
infection. The value of these studies is that they can find abnormalities not seen with
other tests and are a quick means to view the entire skeleton.
The study is performed
by injecting a mildly radioactive compound, a phosphate labeled with technetium, into a
vein in the arm. Depending upon the indication, pictures are then acquired immediately
after the injection, 3 hours later or 24 hours later. There are virtually no side effects
associated with the test and the resultant dose of radiation is small. |
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Ventilation - perfusion lung scans (VQ scans)
The ventilation perfusion lung scan (also known as a VQ scan) is a method for
detecting blood clots in the lungs. Blood clots (thrombi) can form in the veins of the legs
(or other parts of the body) and then travel to and lodge in the lungs causing such
symptoms as shortness of breath and chest pain. This is a potentially very serious
problem.
The scan is performed with two sets of images of the lungs: one of airflow
and one of blood flow. The ventilation (airflow) images are taken after the patient
breaths an aerosol containing a mildly radioactive material (technetium DTPA).
The
perfusion (bloodflow) scan follows and is performed after another radioactive material
(technetium MAA) is injected into the arm. In each portion of the study a set of pictures
are obtained with the patient lying face up on the camera table and the camera positioned
around the lungs.
The radiation dose from this procedure is small and there are virtually
no side effects from this study. |
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Myocardial perfusion scans (cardiac scanning)
A myocardial perfusion scan is a method for detecting abnormalities of blood flow to
the heart. This is done with the intravenous injection of a mildly radioactive tracer,
usually either thallium or sestamibi. The study is typically performed in two parts. The
first is to visualize blood flow during stress. While walking or running on a treadmill, the
radiotracer is injected into an IV. About 15-30 minutes later, the patient is placed on a
table in the camera gantry and pictures of the heart are taken. In patients who cannot
exercise on a treadmill, this part of the test is replaced and performed during the
infusion of a drug that dilates the blood vessels of the heart. The second part of the
test is to repeat the pictures after receiving another injection of the tracer during a
period of rest. If the study shows that blood flow diminishes during exercise but is
normal at rest, an area of ischemia (a cause of chest pain or angina) is identified. The
test may also show that blood flow is abnormal during both exercise and at rest thus
identifying an area of scar or area of dead tissue.
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