How does this imaging work?

The imaging has two parts:

Part 1

In the first part of the test, the heart is stressed. That is, the heart's arteries are expanded (dilated) using a special medication. Healthy or normal coronary arteries dilate more than unhealthy or partially blocked arteries.

Once the blood vessels are dilated, a small amount of a radioactive imaging agent is injected. The imaging agent tends to concentrate in those parts of the heart that have the best blood flow. The imaging agent emits signals that can be detected by a special type of camera.

Images taken by the camera show if any part of your heart is not getting enough blood.

Myocardial perfusion images

Part 2

In the second part of the test, two sets of pictures are taken. The first set of images shows the arteries of the heart when the blood vessels are dilated. The second set shows the heart during normal functioning, referred to as at "rest". The two sets of images are compared.

A relatively healthy heart shows little or no difference between images taken during stress and those taken at rest.

In a heart with partially blocked arteries, images taken during stress are different from those taken at rest.

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How do you prepare?

For this test, certain ingredients that exist in foods and medications (even in tiny amounts) may interfere with the test. These ingredients include caffeine, theophylline and dipyridamole. What does this mean?

For 24 hours before your test, please do not eat or drink any of the foods, and do not take any of the medications, on the list below.

NO	coffee or tea that is brewed, instant, iced or decaffeinated
NO	colas or other soft drinks that contain caffeine, including those labeled, caffeine-free
NO	chocolates, including candies, frosting, cookies, pies, cocoa, and chocolate milk
NO	aspirin products that contain caffeine, such as Anacin and Excedrin
NO	Persantine (dipyridamole)
NO	theophylline or theophylline containing products such as Constant-T, Primatene, Quibron, Slo-Phylline, or Theo-Dur

This is only a partial list. Check product labels or ask your pharmacist or doctor to be sure of what products to avoid before your test. You should avoid products that contain caffeine, theophylline, and dipyridamole. This will help assure that your test will go as smoothly as possible.

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What happens during the test?

During the test you will be lying on your back. A blood pressure cuff is placed on one arm, and a small intravenous needle (IV) is inserted in your other arm. Small round pads are placed on your chest that are attached to an electrocardiograph (ECG). This allows your doctor to monitor your heart rhythm.

The dilating medication is injected over a period of approximately 6 minutes. The imaging agent is injected midway through the 6 minutes. When the injections are over, the doctor will continue to monitor your heart for a couple more minutes.

As the dilating medication is given, you may feel flushed, chest pressure/pain, shortness of breath or some other discomfort. This is perfectly normal, but it is important to tell the doctor just what you are feeling. Usually, these effects disappear by themselves within a minute or two after the injection is over. However, injection of another medication may be required to stop the action of any persistent feelings.

It's possible that you may feel some of the medication's effects for up to 24 hours after the test. If so, please contact your doctor.

The next portion of the test involves taking pictures or "imaging" of the heart.

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What happens during imaging?

During this portion of the test, you will rest on your back, usually with your arms comfortably extended above your head. For the next approximately 45 minutes, images of the blood flow of your heart are taken by a special camera. It's important that you lie still during this procedure to ensure the best possible images. The camera is large but should not worry you. It doesn't even come in contact with you during the procedure, and it doesn't hurt or emit any radiation.

You may be asked to return a couple hours later for a second round of images when your heart is at "rest". These images are compared to the images obtained during the first part of the test.

When your myocardial perfusion imaging is complete, your doctor will know more about the blood flow to your heart muscle and your health.

Click to go to full size version (174K) "imaging" of a heart.

This image is a quality control screen for the technologist and physician to evaluate the quality of the image data before interpretation. This image of a 56 year old male displays the evaluation of cardiac motion, number of counts in the heart (statistical quality), orientation, and surrounding tissue. Click to view the full size image. (196.5K)

This is the image the physician uses to interpret the cardiac perfusion with a severe inferolateral defect at Stress, with some reversibility at Rest. This display allows the cardiologist to look at the blood supply in the heart as a series of beating heart slices, 2 dimensional polar plots, and as a 3D object. Additionally, a Ejection Fraction report (EF report) is reported on the same screen. Click to view the full size image (208.3K).

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