Whether it's called multislice CT (MSCT), multidetector CT (MDCT), cardiac CT or cardiovascular CT, the CT stands for "Computed Tomography", a way of measuring parts of the anatomy by sections (originally known as "Computed Axial Tomography" or CAT scans). Single CT scans are widely used in medical imaging, but have been less useful for imaging the heart, since a beating heart doesn't stand still for a picture.

Now the development of multiple detectors, or Multislice CT systems has allowed imaging of the heart, which moves as it beats, with a level of detail not previously available.

A few years ago the patient would move on to a cardiac catheterization, during which a physician inserts a catheter into the circulatory system, advances it to the heart and injects dye into the coronary arteries. The physician then makes an X-ray (cine-angiography) movie from several different angles, develops the film and sits at a viewing machine to analyze the 35mm motion pictures. More recently, the film may have been replaced by digital video. In either case, because the X-ray is a "shadow" image that is two-dimensional, the cardiologist has to interpret a number of different "camera angles" that were shot to determine the presence and shape of any obstructions to the blood flow.

But a much better diagnostic option would be a detailed 3D virtual model of the patient's heart -- so that the cardiologist could rotate, zoom and move through the heart's anatomy at any angle at will, as if it were a video game. And without impacting on the patient!

Multislice CT angiography provides this 3D model, and it is revolutionizing cardiac imaging to the point where a separate Society of Cardiovascular Computed Tomography (scct.org) has recently been formed to set standards for training and interpretation.

Multislice CT systems with 16 or more detectors have made a quantum leap into imaging of the coronary arteries. A 256-slice system is now in development that will image the entire heart in a single beat.

In less than 30 minutes, without the invasiveness of a cardiac catheterization, a patient can have an MSCT done to determine if there are any arterial blockages that require an intervention, such as an angioplasty or stent. The only immediate impact on the patient is an IV with iodine-containing contrast and possibly a beta-blocker to slow the heart beat (the equivalent of saying "cheese" and holding still for the photographer).

Although MSCT does entail a higher radiation dose from that experienced during a standard catheterization, mitigating this risk is the fact that the patient is not exposed to the complications that sometimes accompany cardiac catheterization (angiography). Additionally, newer technology developments and scanning methods that reduce the necessary radiation exposure are ongoing.

If no blockages are found, MSCT provides a less invasive and less expensive method of ruling out the need for additional intervention.

Who Does the Procedure: MSCT can be done by a cardiologist, radiologist or technologist trained in this specific imaging modality. Because the MSCT scan reads the entire upper torso, a growing number of heart and vascular centers are having both cardiology and radiology specialists"read" the results -- the cardiologist for coronary disease, and the radiologist to identify other potential non-cardiac problems, such as cancers, etc.

Patient Preparation: As with any procedure that involves radiation, tell the technologist if you are pregnant. You may be asked not to eat or drink for a while prior to the procedure. You will need to remove any metallic jewelry, etc. During the procedure, you will be injected with some iodine-containing dye, as well as beta-blockers, so let the doctor know if you have a known allergy to those.