What is ultrafast CT?

In conventional x-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a regular x-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography (CT or CAT) scan, the x-ray beam moves in a circle around the body. This allows many different views of the same organ or structure, and provides much greater detail. The x-ray information is sent to a computer that interprets the x-ray data and displays it in 2-dimensional form on a monitor. While many images are taken during a CT scan, less radiation is received by the patient than with a single standard x-ray, in many cases.

A new technology called ultrafast CT (computed tomography) has begun to be used in the past few years to diagnose heart disease. Ultrafast CT can take multiple images of the heart within the time of a single heartbeat, thus providing much more detail about the heart's function and structures, while also greatly decreasing the amount of time required for a study. Ultrafast CT can detect very small amounts of calcium within the heart and the coronary arteries. This calcium has been shown to indicate that lesions which may eventually block off one or more coronary arteries and cause chest pain or even a heart attack are in the beginning stages of formation. Thus, ultrafast CT scanning is being used by many physicians as a means to diagnose early coronary artery disease in certain people, especially persons who have no symptoms of the disease.

Why is ultrafast CT performed?

Ultrafast CT is currently used primarily for the diagnosis of coronary artery disease, particularly in people who have no symptoms of the disease but who have significant risk factors for the disease. An ultrafast CT scan may also be scheduled for:

• suspected mass or tumor within the heart.
• suspected aortic aneurysm (a weakened spot in the wall of the aorta, the main artery which carries oxygenated blood away from the heart to the body).
• assessment of heart tissue damage after MI (myocardial infarction, or heart attack).
• assessment of the patency (openness) of coronary artery bypass grafts.
• assessment of the pericardium (the outer sac surrounding the heart).
• assessment of suspected congenital conditions of the aortic arch (the arch-like portion of the aorta).
• assessment of suspected aortic dissection (tearing of the lining of the aorta).

How is ultrafast CT done?

Ultrafast CT is usually performed on an outpatient basis. There is no preparation necessary prior to the procedure. Although each hospital may have specific protocols in place, generally an ultrafast CT procedure follows this process:

1. The patient will lie on the narrow table of the scanner and will be positioned by a staff member.
2. The patient will be given a call bell to hold in his/her hand so that he/she can notify the staff if he/she needs assistance.
3. Once the patient is positioned correctly, the table will slide slowly into the scanner. The patient's arms will be at his/her sides.
4. Once inside the scanner, the staff will give instructions through the speakers. The patient will hear clicking noises as preliminary adjustments are made.
5. Once the procedure begins, the patient will need to be very still at all times so that movement will not adversely affect the quality of the images.
6. At intervals, the patient will be instructed to hold his/her breath, or to not breathe, for a few seconds. He/she will then be told when he/she can breathe. The patient should not have to hold his/her breath for longer than a few seconds, so this should not be uncomfortable.
7. Once the procedure is finished, the table will slide out of the scanner. The patient will be assisted in getting up.
8. The patient may be asked to wait for a short time while the radiologist reviews the scans to make sure they are clear and complete. If the scans are not sufficient enough to obtain adequate information, additional scanning may be necessary.
9. Once the scanning has been completed, the patient may dress, if necessary, gather his/her personal belongings, and leave.