There are different nuclear cardiac scans, each of which uses different radiotracers.
Cardiac imaging includes:
Nuclear cardiac scans are performed for a number of reasons.
A) MIBI CARDIAC SCAN:
A myocardial perfusion scan is conducted to evaluate blood flow (perfusion) to the heart muscle during exercise and rest.
During a cardiac perfusion or MIBI scan a small amount of radioactive tracer is injected into the bloodstream after a period of exercise or rest.
During exercise testing, echocardiogram (ECG) leads are attached to the chest, arms, and legs to monitor the heart rate. You will be asked to walk on a treadmill, or pedal on a stationary bike, slowly at first, and then the speed will increase until your heart rate reaches a certain target. Once your heart rate is at the correct rate, or if you develop chest pain during exercise, your doctor will inject the radioactive tracer intravenously. There is normally a period of about 45 minutes to an hour before imaging will commence. A camera then records images of the radioactive tracer in the heart. These cardiovascular images allow your doctor to properly assess perfusion or blood flow in the distribution of the coronary arteries.
3h after the initial stress test, a resting scan is performed. A second injection of Tc-99m MIBI is administered intravenously with the patient at rest. The second scan is performed 1h after the 2nd injection. The scan time is about 20 min.
In certain cases, if patients cannot exercise, a physiological stress test is performed where a substance called Persantin is injected slowly prior to administration of MIBI.
Preparation for a Persantin MIBI scan:
B) MUGA SCAN:
A multigated-acquisition scan is helpful in cases where it is necessary to evaluate the function of the heart by measuring blood flow into the left ventricle, to assess the function of both ventricles and to see if there are any abnormalities in the contraction of the heart muscle.
There is no special preparation for this test.
A blood sample (5 ml) is withdrawn from a vein into a syringe. The RBC are isolated and labelled with radioactivity (normally Technetium) in a laboratory. The patients' RBC are resuspended in their own serum and reinjected while laying under a gamma camera.
The patient will be linked with an ECG monitor during the procedure. Images are obtained in several projections. The imaging procedure normally takes about 40 min.