Module 4/diagnostic Tests And Procedures/nuclear Medicine Scans

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POSITRON EMISSION TOMOGRAPHY (POS-i-tron e-MISH-un to-MOG-rah-fe): 

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also known as: PET Scan
*uses substances such as glucose tagged with a positron-emitting isotope to measure body functions (metabolic activity),chemical and physiological changes.
*allows study of body function,can detect alterations in biochemical processes that suggest disease before changes in anatomy are apparent on other imaging tests such as MRI or CAT (MRI/CT show views of shape/size on internal structures only)
*in addition, whole body imaging with PET allows doctors to examine most organ systems with a single scan which may eliminate the need for multiple testing.
Radioactive substances that release radioactive particles called positrons are injected into the body and travel to areas of the brain.. Because of the way that the positrons are released, cross-sectional color pictures can be made showing the location of the radioactive substance. This test is used to study disorders of the brain and to diagnose strokes, epilepsy, schizophrenia and migraine headaches.
*primarily applied to the work-up of cancer, in diagnosing, staging, and monitoring cancer.

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BONE SCAN:  

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*to find abnormal areas within bones or joints
A radioactive substance is injected intravenously and its uptake in bones is detected by a scanning device. Tumors in bone can be detected by increased uptake of the radioactive material in the area of the lesion.

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BRAIN SCAN:

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*to assess blood supply to the brain
A radioactive substance is injected intravenously and collects in any lesion that disturbs the natural barrier that exists between blood vessels and normal brain tissue (blood-brain barrier), allowing the radioactive substance to enter the brain tissue. A scanning device detects the presence of the radioactive substance and thus can identify an area of tumor, abscess, or hematoma.

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GALLIUM SCAN (GAL-le-um Skan):  

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*to look for areas of hidden infection in the body (Gallium collects in areas of inflammation)
*to detect infection or tumor
Radioactive gallium is injected into the bloodstream and is detected in the body using a scanning device that produces an image of the areas where gallium collects.
The gallium collects in areas of tumors (Hodgkin's disease, hepatoma, various adenocarcinomas) and in areas of infection

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MYOCARDIAL SCAN (mi-o-KAR-de-al skan):  

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Also called a Thallium Scan
A radioactive substance (thallium chloride-201) is injected intravenously and travels to the heart muscle while the patient is at rest or exercising.
Imaging shows up areas that have inadequate collection of radioactive substance, such as areas of blocked blood vessels 

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Nuclear Medicine Scans

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Radioisotope scanning--invloves the use of a small amount of radioactive material that is injected, inhaled or swallowed and then a rectilinear scanner,gama camera or scintoscope is used to read or detect the isotope within the organ.
*It is based on the fact that various organs absorb or concentrate specific minerals or hormones, but these substances do not show-up on a regular x-ray. If made radioactive by a radioisotope, they can be seen and if organ is not functioning propery, too little or too much of the substance will be taken up or it will be concentrated in some parts of the organs but not others. The organ will look different on screen if a portion of the organ does not show up, it may indicate presence of a tumor.

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PULMONARY PERFUSION SCAN (PUL-mon-ar-e per-FU-shun skan): 

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*measures supply of blood through the lungs
Radioactive particles are injected intravenously and travel rapidly to areas of the lung that are adequately filled with blood.
Regions of obstructed blood flow due to tumor, blood clot, swelling and inflammation can be seen as nonradioactive areas on the scan.

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PULMONARY VENTILATION SCAN (PUL-mon-ar-e ven-ti-IA-shun skan):

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*used to evaluate the ability to aerate all portions of the lungs.
Radioactive gas (xenon-133) is inhaled, and a special camera detects its presence in the lungs.
The scan is used to detect lung segments that fail to fill with the radioactive gas. Lack of filling is usually due to diseases that obstruct the bronchial tubes and air sacs.
This scan is also used in the evaluation of lung function prior to surgery.

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THYROID SCAN (THI-royd skan): 

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A radioactive iodine chemical is injected intravenously and collects in the thyroid gland. A scanning device detects the radioactive substance in the gland, measuring it and producing an image of the gland.
The increased or decreased activity of the gland is demonstrated by the gland's capacity to use the radioactive iodine.
A thyroid scan is used to evaluate the position, size and functioning of the thyroid gland.