Cardiac Nuclear Medicine
What is 'cardiac nuclear medicine'?
Cardiac nuclear medicine is basically used to diagnose diseases of the heart. The two major areas of detection are what we call myocardial ischemia, and that is the shortage of the blood to the heart muscle in relation to coronary artery disease. The second major area is in the detection of myocardial viability. Those are areas of the heart muscle which are hibernating. They are not dead yet but they are hibernating, and they're not contracting. So we need to detect those areas of the heart so that we know if we need to restore the blood flow to those areas of the heart, so they come back and contract and contribute to normal cardiac function.
What is an 'ECG'?
ECG stands for electrocardiogram. Essentially, it's a record of the electrical activity of the heart. It is obtained by placing electrodes into the appropriate places on the surface of the body and connecting it to an electrocardiograph, which records this electrical activity of the heart.
What is 'myocardial perfusion scanning'?
Myocardial perfusion scanning is basically a nuclear medicine technique where we inject the patient intravenously with appropriate tracer designed for looking at perfusion or blood flow to the cardiac muscle. For example, we can give technetium nitro ionine system maybe or tetrofosmin, or thallium -201-chloride which basically go to the coronary artery into the heart muscle and tells us how the muscle is being perfused. That's what's called the cardiac perfusion imaging.
What are the benefits and risks of myocardial perfusion scanning?
The benefits of myocardial perfusion imaging is tremendous. Basically it's a very time tested procedure for corneal artery disease in patients. That's the major benefit for us, to establish which patients who are presenting with chest discomfort actually have cardiac origin disease, as opposed to other causes of chest discomfort. The risks of myocardia perfusion scanning are basically similar to what we discuss with general local medicine. They are very small in relation to the radioactivity which is administered to the patient. So the benefit to risk ratio is huge.
What is 'cardiac gating'?
Cardiac gating is when we connect a patient and use the electrocardiogram (ECG) to synchronize the imaging acquisition from the camera system when we're doing cardiac imaging tests. The reason for that is we can actually look at the function and beating of the heart during imaging acquisition. This is important because we can get information about cardiac function with such indices as, for example, left ventricular ejection fraction; which is an important parameter for us to know. So gating is used in conjunction with imaging to give us functional data on the heart.
What is a 'stress thallium test'?
People usually call it a stress thallium test, because previously thallium was one of the most common tracers used, but basically it refers to the procedure of doing a cardiac profusion imaging study, and in that, we normally have a patient imaged after or during a type of cardiac stress. Most commonly, it's when a patient runs on a treadmill or on a bicycle ergo meter, but it can also be done pharmacologically, and not necessarily through some sort of a dynamic exercise. That's the stress portion of it and the thallium really refers in general to the tracer that is administered. It could be cystamibi or tretramospine or thallium and that's basically what is within that term of stress thallium.
How can I prepare for a cardiac nuclear medicine test?
The patient is asked to fast for a few hours prior to coming to the nuclear cardiology laboratory. We want them to be well hydrated. They can take their medicines as before. If they are going to be stressed pharmacologically, which, I can mention the names, are Dipyridamole, for example, or Adenosine. Those also require the patient to stay away or to not drink caffeinated products including coffee, tea or soft drinks that have caffeine in them. This is because the caffeine interferes with the effectiveness of those drugs that we use during the procedure. Therefore, the preparation is quite simple and, again, depending upon what type of stress we use, we may ask them to stay away from caffeinated products.
What does the equipment used in a cardiac nuclear medicine test look like?
The equipment are basically what we call single-photon emission computed tomography, or SPECT systems. These are usually gamma camera systems that have what we call two heads or three heads. The heads are basically the detectors which surround the patient, and they are able to acquire or record the gamma rays that come off of the patient, and that data is used by the computer to form an image of the heart.
How is a cardiac nuclear medicine test performed?
What will I experience during a cardiac nuclear medicine test?
