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Thallium Imaging (Cold-Spot Myocardial Imaging; Thallium Scintigraphy)
Thallium Imaging (Cold-Spot Myocardial Imaging; Thallium Scintigraphy)
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Thallium Imaging (Cold-Spot Myocardial Imaging; Thallium Scintigraphy)
Category: Cardiovascular system.
Subcategory: Nuclear medicine.
Material studied: Image created by nuclear-scanning equipment.
Estimated cost of test: Resting $150.00 to $300.00; exercise $300.00 to $500.00.
Patient time for test: 1 to 1-1/2 hours.
Reliability of test results: Good. Other tests, studies and clinical observations are necessary to establish a precise diagnosis.
Available as home self-test? No.
BEFORE THE TEST
Purpose of test:
Assesses amount of blood reaching heart muscle.
Determines location and size of injured muscle after myocardial infarction*.
Diagnoses narrowing of arteries, such as coronary-artery disease*.
Evaluates how grafted vessels work after coronary-artery bypass surgery*.
Evaluates effectiveness of anti-anginal therapy or balloon angioplasty.
Where is test performed?
Commercial laboratory, hospital, doctor's office, outpatient or freestanding surgical facility.
Who performs test?
Lab technician, nurse, doctor.
Risks and precautions:
May be hazardous if you have impaired neuromuscular function, locomotor disturbances, acute myocardial infarction*, myocarditis*, aortic constriction, acute infection, diabetes*, digitalis toxicity, recent pulmonary infarction*.
May be hazardous if you are pregnant.
Test is stopped if you develop chest pain, labored breathing, fatigue, faintness, low blood pressure, ischemic EKG changes, significant arrhythmias*, pallor, clammy skin, confusion or a staggering gait.
Patient preparation:
Activity--Avoid tobacco for 24 hours.
Diet--Avoid alcohol and caffeine for 24 hours before the test. Don't eat for 3 hours before the test, although you may eat a light meal earlier.
Medicines--No changes necessary.
Disrobing--Remove all clothing. Put on surgical gown.
THE TEST
Sensory factors:
Touching--You will experience minor pain for a short period when the radioactive material is injected into your vein. You may be uncomfortable for 35 to 45 minutes when you assume the positions the technician requests. Lie still while the scanning takes place, or the test may need to be repeated. Hands above head and feet frequently become numb during the examination. Ask for a blanket if you are cold.
Seeing--You will see strange-appearing heavy equipment in a small space. You will see the technician, nurse or doctor, the basket or tray to hold the equipment, the needles, syringes, collecting tubes and bandages.
Hearing--You will hear the sounds of scanner machine.
Feeling--You may feel intimidated by the large equipment. Some degree of apprehension or fear is normal and should be expected. This discomfort disappears when the test is completed. You may also feel uncomfortable for a short while if small, enclosed space causes you discomfort.
Tasting and Smelling--Not affected.
Equipment used:
I.V. injection of thallium.
Scintillation camera.
Blood-pressure cuff.
Electrodes.
Electrocardiogram.
Treadmill (for stress imaging).
Thallium Scintigraphy)
Description of test:
You or a close relative will be required to sign a consent form after the procedure has been explained to you.
Skin is cleaned with antiseptic.
A radioactive chemical is injected into a vein, usually in the arm.
Multiple images of your heart are made.
Follow technician's instructions regarding positions.
The scintillation camera or scanner detects rays emitted from the radioactive chemical injected into your body.
Rays are converted into images displayed on a video screen for interpretation.
Electrocardiogram (EKG) and blood-pressure readings are taken while you walk on a treadmill or pedal a stationary bicycle.
Doctor and emergency equipment are in testing area at all times during test.
Several areas on your chest and possibly your back are cleaned and shaved to prepare the skin for the electrodes. Electrode sites may itch slightly, but you won't feel any current from them.
Monitor is started.
Readings are taken with you in a resting condition. The pattern of the heartbeat segments recorded are compared to normal heartbeat patterns.
Your blood pressure and heart rate are checked periodically.
Treadmill starts at a slow speed with a flat incline. You walk on it, balancing on a support in front of you. Don't bear your weight on the support.
Speed and slope are increased until your heart reaches a predetermined target rate.
Exercise stops. EKG continues to monitor your heart's activity for 10 to 15 minutes.
AFTER THE TEST
Immediate post-test care:
Rest after exercising.
Activity after test:
If you are scheduled for further scanning, rest between the scans. You will be restricted to a diet of clear liquids.
Time before test results available:
Time before results are reported to the doctor or patient varies from a few minutes to a few days.
TEST RESULTS
Test values:
Test results are determined by studying images.
Normal values:
No anatomical or functional abnormalities.
What ABNORMAL may indicate:
Ischemia* from coronary-artery disease*.
Myocardial infarction*.
Closure or narrowing of coronary-artery bypass surgery*.
Taking these drugs may affect test results:
None expected.
Other factors that may affect test results:
Use of tobacco before test.
Alcohol.
Caffeine.
Failure to follow dietary restrictions.
Cold spots could also result from formation of nodules resulting from breast implants, cardiac contusion, chronic disease of unknown cause, coronary spasm, electrodes or myocardial fibrosis*.
If you have coronary-artery disease* and no cold spots show, it could result from insignificant obstruction, inadequate stress, delayed imaging, single-vessel disease* or collateral circulation.
*See Glossary.
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From Complete Guide to Medical Tests by H. Winter Griffith, M.D. Copyright by Fisher Books. Electronic rights by Medical Data Exchange.
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