Advantages over regular Angiography:
CT technology uses several small detectors positioned in an arc around the patient. Each one of these detectors records a single X-ray image at a time. As the scanner frame spins around the patient, the detectors take snapshots of the fan-shaped beam of x-rays after it passes through the patient’s body. Several hundred images are recorded in one turn of the detector. These are then analysed with the help of computer programs for appropriate display and analysis.
You will be required to sign a form giving your consent for the procedure. Our dedicated caregivers/technicians will guide you through each step of the examination.
Local leakage of contrast material at the site of injection can cause pain. If you feel any pain in this area during contrast injection, please inform any of the attending persons immediately.
The procedure is not advised for pregnant women, especially during the first three months of pregnancy. Mothers who are breastfeeding at the time of the examination, should consider pumping out breast milk before the procedure for immediate use. Breast feeding can be resumed within a few hours by the time contrast material has usually left the body. Just like all of the other tests based on exposure to X-rays, there is a risk of cancer attributable to radiation exposure at CT-A. This risk has been considerably reduced with technological advances.
In CT Vascular angiography (CTA), a contrast material (also known as “dye”) is injected into a vein to produce detailed images of both blood vessels and tissues.
Metal objects including jewelry, eyeglasses, dentures and hairpins may affect the CT images and should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work.
You may be asked not to eat or drink anything for several hours beforehand, especially if a contrast material will be used in your exam. You should inform your physician of any medications you are taking and if you have any allergies. If you have a known allergy to contrast material, or “dye,” your doctor may prescribe medications to reduce the risk of an allergic reaction.
Also inform your doctor of any recent illnesses or other medical conditions, and if you have a history of heart disease, asthma, diabetes, kidney disease or thyroid problems. Any of these conditions may increase the risk of an unusual adverse effect.
Women should always inform their physician and the CT technologist if there is any possibility that they are pregnant.
In a conventional x-ray exam, a small burst of radiation is aimed at and passes through the body, recording an image on photographic film or a special image recording plate. Bones appear white on the x-ray; soft tissue shows up in shades of gray and air appears black.
With CT scanning, numerous x-ray beams and a set of electronic x-ray detectors rotate around you, measuring the amount of radiation being absorbed throughout your body. At the same time, the examination table is moving through the scanner, so that the x-ray beam follows a spiral path. A special computer program processes this large volume of data to create two-dimensional cross-sectional images of your body, which are then displayed on a monitor. This technique is called helical or spiral CT.
CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When the image slices are reassembled by computer software, the result is a very detailed multidimensional view of the body’s interior.
Refinements in detector technology allow new CT scanners to obtain multiple slices in a single rotation. These scanners, called “multislice CT” or “multidetector CT,” allow thinner slices to be obtained in a shorter period of time, resulting in more detail and additional view capabilities.
Modern CT scanners are so fast that they can scan through large sections of the body in just a few seconds. Such speed is beneficial for all patients but especially children, the elderly and critically ill.
When a contrast material is introduced to the bloodstream during the procedure, it clearly defines the blood vessels being examined by making them appear bright white.
A small amount of contrast material (“dye”) may initially be injected through the IV to determine how long it will take for the full amount to reach the area under examination. During scanning, the table will then move to the start point and then move relatively rapidly through the opening in the machine as the actual CT scanning is performed. An automatic injection machine connected to the IV is usually used and will inject contrast material at a controlled rate both prior to and during scanning. In some cases, especially in children, the injection is given by hand with a syringe by a person in the CT room, often a nurse.
Occasionally, sedation is needed for children to keep them still during the scanning. This usually needs to be prearranged when the CT scan is scheduled as there will be special instructions. For example, eating and drinking must be stopped prior to the sedation procedure, and arrangements should be made for monitoring during recovery following the scan.
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.