A CT Angiography (CTA) Brain scan is a specialized medical imaging technique designed to visualize the blood vessels supplying the head and neck. This non-invasive test uses a standard Computed Tomography (CT) scanner combined with an injected contrast material. The procedure’s goal is to produce highly detailed, cross-sectional images of the arteries and veins. By highlighting these vascular structures, the CTA Brain provides clinicians with a clear map of the cerebral circulation.
Why Brain CTA Imaging is Performed
Accurately mapping the brain’s vascular network is important for diagnosing conditions involving blood flow disruption or structural abnormalities. Physicians often order a CTA Brain when they suspect issues requiring immediate, high-resolution visualization of the blood vessels. This imaging technique is utilized frequently in emergency situations, such as evaluating a patient presenting with symptoms of a sudden neurological event.
A primary indication for this scan is the diagnosis of cerebral aneurysms, which are abnormal, balloon-like bulges in a blood vessel wall. Visualizing the size, shape, and exact location of these weakened areas helps determine the risk of rupture and plan intervention. The scan also plays a significant role in stroke evaluation by identifying blockages or severe narrowing (stenosis) within arteries that restrict blood flow to brain tissue.
The CTA is also used to detect arteriovenous malformations (AVMs), which are abnormal tangles of blood vessels connecting arteries and veins, bypassing the capillary system. These malformations can lead to bleeding or seizures, and the scan provides detail necessary for surgical planning. The imaging is often performed before neurosurgical procedures to map the vascular supply to a tumor or after head trauma to assess for vascular injuries like dissections or hematomas.
How the Procedure Works
The CTA Brain procedure begins with the placement of an intravenous (IV) line, typically in the arm or hand, necessary for administering the contrast agent. The patient then lies down on a motorized table that slides into the doughnut-shaped opening of the CT scanner. The patient must remain completely still throughout the process to ensure the resulting images are clear.
The specialized, iodine-based contrast material is injected rapidly through the IV line. As the contrast enters the bloodstream, the patient may experience a brief sensation of warmth or flushing across the body, sometimes accompanied by a temporary metallic taste. These sensations are normal and quickly subside after the injection is complete.
The CT scanner utilizes “bolus tracking” to precisely time the image acquisition. This automated process ensures the rapid sequence of X-ray images is captured exactly when the contrast material peaks within the brain’s arteries. The scanner rotates around the patient’s head, acquiring multiple cross-sectional images, or “slices,” in seconds. These raw images are then processed by a computer to create detailed two-dimensional views and three-dimensional reconstructions of the cerebrovascular system.
Preparation and Safety Considerations
Preparing for a CTA Brain scan involves steps designed to maximize image quality and ensure patient safety, particularly regarding the contrast material. Patients are usually instructed to fast from solid foods for four to six hours before the procedure, though clear liquids may be permitted. All metal objects, including jewelry, hairpins, and certain dental work, must be removed as they can interfere with X-ray signals and cause image distortion.
The iodine-based contrast agent requires the care team to assess the patient’s kidney function beforehand. A recent blood test measuring creatinine levels is often required, as the kidneys filter the contrast from the body. Patients with pre-existing kidney issues may need special precautions or alternative imaging.
Patients must inform the healthcare provider if they take the diabetes medication metformin (Glucophage). The combination of metformin and iodine contrast can temporarily affect kidney function, so patients may be advised to stop taking the medication for 48 hours after the scan. Any history of allergies, especially to iodine, shellfish, or prior contrast dyes, must be shared, as this may necessitate pre-treatment to minimize the risk of an allergic reaction.
The procedure involves exposure to a small amount of ionizing radiation from the CT scanner. Medical facilities operate under strict guidelines to keep the radiation dose as low as reasonably achievable (ALARA principle). For most patients, the diagnostic benefit of obtaining a clear image of the brain’s blood vessels outweighs this minimal risk.
What the Scan Detects
When reviewing the CTA images, the radiologist focuses on visual evidence of vascular health and disease. The high-resolution images clearly outline the interior of the cerebral arteries, allowing for the precise identification of acute blood clots (thrombi) that signify a blocked vessel. Detecting these occlusions is time-sensitive and informs immediate treatment decisions in cases of suspected stroke.
The scan is designed to highlight areas of narrowing or focal outpouchings in the vessel walls. This includes measuring the extent of stenosis and characterizing any detected aneurysms. Radiologists determine the exact size, neck width, and orientation of an aneurysm, which are factors in treatment planning.
The detailed three-dimensional reconstructions provide a comprehensive view of the entire cerebrovascular network, including the Circle of Willis (a network of arteries at the base of the brain). This visual clarity helps assess the overall integrity of the arteries and aids in identifying subtle abnormalities like vascular dissections.