CT and 3D Subtraction Angiography


Computed tomography angiography, or CTA, is a safe outpatient procedure that helps locate and capture images of an aneurysm in the brain. This technology uses specially designed X-rays and intravenous dyes or contrast agents to see the detailed anatomy of the blood vessels throughout the body.

CTA is a less invasive and a more patient-friendly procedure than standard catheter angiography, which requires placing a catheter into an artery close to the area being examined. With CTA, the contrast agent is injected into a vein instead of an artery as in standard catheter angiography. Using the vein is less difficult and has a very low risk of complications. As a result, the patients typically leave immediately following the procedure and can resume normal activities.

Three-dimensional, or 3-D, imaging allows health-care providers to consistently obtain high-quality images, which helps them formulate an accurate and definitive diagnosis of intracranial aneurysms.

Subtraction angiography refers to the process of removing or subtracting objects from an image that may be obstructing the area we are most interested in viewing. For example, if health-care providers want to study blood vessels, 3-D imaging will allow them to remove other structures in the image so they may view the vessels better.

This procedure is considered to be as reliable and as safe as conventional angiography. It also reduces procedural time and decreases the need for the injection of a contrast agent.

Procedural Details

First, the patient receives an IV and is placed on the CT scanning table. The patient then receives an intravenous contrast while the CT scanner captures images of the area of interest. Most people experience a temporary warming sensation as the contrast is administered. This feeling quickly dissipates. Once the scan is complete, the IV is removed.

The real work of CTA comes after the images are acquired. Radiologists use powerful 3-D computer workstations to process the images captured by the CTA, evaluate the source data and create real anatomic displays of the vessels. Then a team of specialists will discuss the outcome of these initial treatments and make a joint decision to proceed with either endovascular or microsurgical treatment.

CT angiography is usually followed by intra – arterial digital subtraction angiography with 3-D imaging. Subtraction refers to a procedure by which we suppress interfering structures in the area being examined so that the arteries become clearly defined.


CT Angiography (CTA) should be avoided in patients with kidney disease or severe diabetes, because X-ray contrast material can further harm kidney function. If you feel any pain in this area during contrast material injection, you should immediately inform the technologist.



Examining arteries in the brain may help reach a correct diagnosis in patients who complain of headaches, dizziness, ringing in the ears or fainting. Injured patients may benefit from CTA if there is a possibility that one or more arteries have been damaged. In patients with a tumor, it may be helpful for the surgeon to know the details of arteries feeding the growth.

The CT angiography procedure can also detect the narrowing of blood vessels, leading to corrective therapy of those vessels. Early detection and treatment can prevent these vessels from worsening over time. The CTA method also is capable of displaying the anatomical detail of blood vessels more precisely than MRI or ultrasound.


A patient could have an allergic reactions to CTA treatment. If you have a history of allergy to X-ray dye, you may be advised to take special medication for 24 hours before CTA to lessen the risk of allergic reaction. Women should always inform their doctor or X-ray technologist if there is any possibility that they are pregnant. And if you are breastfeeding at the time of the exam, you should ask your radiologist how to proceed.

It may help to pump breast milk ahead of time and keep it on hand for use after CTA contrast material has cleared from your body. Pregnant women, especially those in the first three months, should not undergo CTA or any exam that exposes them to x-rays.

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