A CT scan is a test that combines X-rays and computer technology to produce cross-sectional images (often called slices) of the body. Angiography is a test in which a special dye (properly referred to as contrast) is injected into the blood vessels through a catheter, making veins and arteries visible on an X-ray. When an angiography is used to diagnose an arterial condition, it is called an arteriogram. When an angiography is used to diagnose a venous condition, it is called a venogram. During CTA, contrast dye is injected into a vein as opposed to an artery, which makes it a less invasive alternative to traditional angiography.
CTA may be used to diagnose conditions of the vascular system, such as:
- Peripheral Artery Disease (PAD)
- Deep Vein Thrombosis (DVT)
- Pulmonary emboli
Getting Ready for CTAFor several hours leading up to CTA, you should avoid eating and drinking. Any medications you take will most likely be okay to continue. However, it is important to let your doctor know your medications in case they may increase complications from the procedure. All jewelry and other metal must be removed before the procedure begins because it may interfere with the X-ray images. Additionally, you will likely be asked to wear a hospital gown for the duration of the test.
During Your CTATo begin, contrast dye will be injected into a vein (usually in the hand or arm) by an automated machine that operates at set intervals throughout the procedure. The contrast dye may produce minor side effects such as a warm sensation and/or nausea.
To ensure the best possible image quality, you must stay extremely still while lying on the scan table once it slides into the gantry (the o-shaped machine that contains the scanning equipment). Only the portion of the body undergoing testing will need to be inside the gantry, which is quiet and fairly open. The scanner will be operated by a medical technician who will be watching and speaking to you from an adjacent room.
The gantry contains X-ray tubes that rotate in an “o” shape and direct beams of low-dose X-rays over the body in an arc pattern. The X-ray beams are then reflected onto a detector that is located opposite the X-ray source. Once one arc of X-rays is complete, the scan table moves forward, and another X-ray arc is created. This process repeats until the area being examined has been thoroughly covered. During this process, you will need to stay still and may even need to hold your breath for up to 25 seconds at a time.
Modern CTA can record a vast amount of detailed pictures in a very short time. During the scan, the detector transmits the X-rays to a computer that uses the information to create a 3-D image.
Normally, a CT angiography procedure takes 20 minutes to one hour.
After CTA, your doctor will recommend drinking a lot of fluids to help eliminate the contrast dye from your system and to prevent dehydration. Otherwise, you should be able to return to your normal activities right away.
Risks & ComplicationsCT angiography uses radiation to produce the X-rays needed for imaging. The amount of radiation that is absorbed by your body during a scan is small, but repeated exposure can cause the radiation to accumulate in your body and damage cells over time. Because of this, your doctor may choose another type of imaging test if repeat scans are likely.
The most likely complication of CTA is an allergic reaction to the contrast dye that is used for imaging. This can also be the most serious complication. Risk factors for developing complications from contrast dye include having a known allergy to contrast dye or having an existing allergy to iodine. All allergies should be discussed with your doctor prior to the procedure. If your doctor suspects that an allergic reaction may occur, you may be given medication to lessen the risk of having an allergic reaction. Allergic reactions typically occur immediately upon receiving the contrast dye injection and symptoms include flushing, itching, and, in rare instances, difficulty breathing or swallowing. It is important to let your doctor know if any of these symptoms occur.
If the contrast dye leaks under the skin during injection, a minor complication can occur, which may include redness, swelling, or pain at the injection site.
Another complication that can occur from the contrast dye is kidney damage, especially in patients with a prior history of kidney problems. Because the contrast dye is eliminated from the body through the kidneys after CTA, damage to the kidneys is possible. In some cases, administering medications and fluids before the test may reduce your risk of complications. Your doctor will decide if this course of action is right for you and may test your kidney function prior to CTA to determine your risks.
CTA may not be a good choice for patients with:
- An allergy to contrast dye or iodine
- Kidney problems
- Severe diabetes
- Unstable vital signs
- Pregnancy (a fetus may be harmed by radiation)
- A body weight of more than 300 pounds (some scan tables may not support the weight)