What to Expect During a CT Angiography
This examination is usually done on an outpatient basis.
The technologist begins by positioning you on the CT examination table, usually lying flat on your back or on your stomach. Straps and pillows may be used to help you maintain the correct position and to hold still during the exam.
A nurse or technologist will insert an I.V. into a small vein in your arm.
A small dose of contrast material may be injected through the I.V. to determine how long it takes to reach the area under study. During scanning, the table will move to the start point and then move relatively rapidly through the gantry opening in the machine as the actual CT scanning is performed. An automatic injection machine connected to the I.V. will inject contrast material at a controlled rate both prior to and during scanning.
In exams of the coronary arteries or aorta in the chest, electrocardiogram (EKG) leads are usually placed to record heart rate and rhythm during scanning. Your heart rate may be slowed with beta blocker drugs prior to scanning. If heart rate medication is given, it will be monitored during and after the procedure.
You may be asked to hold your breath during the scanning. Any motion, whether breathing or body movements, can affect the quality of the images.
When the examination is completed, you will be asked to wait until the technologist verifies that the images are of high enough quality for accurate interpretation.
Your I.V. will be removed.
With modern equipment, the CT scanning only takes between 5 and 20 seconds to acquire the appropriate images. Your actual time in the scanner room will be longer as the technologist will have to position you on the table, check or place an I.V. line, do preliminary imaging to verify the beginning and end points of the study, and enter the injection and acquisition sequence into a computer.
CT exams are generally painless, fast and easy. With helical CT, the amount of time that you need to lie still is reduced.
Though the scanning itself causes no pain, there may be some discomfort from having to remain still for several minutes.
If an intravenous contrast material is used, you will feel a slight prick when the needle is inserted into your vein. You may have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes. Some patients may experience a sensation like they have to urinate but this subsides quickly.
When you enter the CT scanner, special lights may be used to ensure that you are properly positioned. With modern CT scanners, you will hear only slight buzzing, clicking and whirring sounds as the CT scanner revolves around you during the imaging process.
You will be alone in the exam room during the CT scan. However, the technologist will be able to see, hear and speak with you at all times.
If the patient is a child, a parent may be allowed in the room but will be required to wear a lead apron to prevent radiation exposure.
After a CT exam, you can return to your normal activities. If you received contrast material, you may be given special instructions.
Limitations of CT Angiography
A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table.
CT angiography should be avoided in patients with advanced kidney disease or severe diabetes, because X-ray contrast material can further harm kidney function.
If a patient's heart is not functioning normally, or if there are multiple blocked blood vessels, CT angiograms may be hard to interpret. CT angiograms are not yet as reliable as selective catheter injections (performed after puncture of the artery in the groin) in imaging small tortuous arteries, particularly coronary arteries in the rapidly moving heart.
Nursing mothers should wait for 24 hours after contrast material injection before resuming breast-feeding.
The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare, and radiology departments are well-equipped to deal with them.