What it is (overview)

A CT Head Angio with IV Contrast (also called a CT angiogram (CTA) of the head or brain angiogram by CT) is a specialized CT scan that creates detailed pictures of the blood vessels in the brain and how blood flows through the head. Unlike a standard CT head scan that focuses mainly on brain tissue, a CT angiogram highlights the brain blood supply—the arteries (and sometimes veins) that deliver blood to the brain.

During the test, an iodine-based IV contrast dye is injected into a vein (usually in the arm). The contrast travels through the bloodstream and makes blood vessels show up clearly on the CT images. A computer then reconstructs the scan into high-resolution 3D views so radiologists can evaluate the vessel size, shape, and any blockages or abnormal connections.

What it “measures”/shows: the structure and openness of brain arteries, including whether there is narrowing (stenosis), blockage, abnormal bulging of a vessel wall (aneurysm), or abnormal tangles of vessels (arteriovenous malformation, AVM).

What results can mean (in plain language): a “normal” result typically means the major brain arteries look open and intact, with no obvious aneurysm, severe narrowing, or abnormal vessel connections. An “abnormal” result may indicate a vessel problem that could help explain symptoms such as sudden severe headache, stroke-like symptoms, or certain types of bleeding in the brain. The scan may also provide important information before treatment (for example, planning surgery, stenting, or endovascular procedures).

When & why it's usually done

Doctors commonly order a CT angiogram of the head with contrast when they need a fast, detailed look at the brain's blood vessels—often in urgent settings like the emergency department. It may be recommended if you have symptoms that suggest a problem with blood flow to the brain or a possible blood vessel abnormality.

Symptoms that may prompt this test include: sudden weakness or numbness on one side, facial droop, trouble speaking, vision changes, dizziness or loss of balance, confusion, fainting, seizures (especially new onset), or a “worst headache of your life” that raises concern for bleeding from an aneurysm.

Common reasons it is ordered:

• To evaluate possible stroke or transient ischemic attack (TIA) by looking for an artery blockage or severe narrowing that reduces brain blood supply.
• To look for a brain aneurysm or determine the source of a subarachnoid hemorrhage (bleeding around the brain).
• To detect or better define an AVM or other abnormal vessel connections (arteriovenous fistula).
• To check for arterial stenosis, plaque buildup, or vessel dissection (a tear in the artery wall) that can cause headache, neck pain, or stroke symptoms.
• To help guide treatment planning and follow-up after procedures (for example, aneurysm coiling/clipping, stent placement) when a noninvasive “angiogram” is needed.
• Less commonly, to assess how a brain tumor relates to nearby blood vessels (for example, whether a mass is highly vascular or encasing an artery), depending on the clinical question.

Your clinician may also consider this test based on risk factors such as high blood pressure, smoking, high cholesterol, diabetes, family history of aneurysm, known vascular disease, or certain connective tissue disorders. Because this test uses contrast and radiation, your care team will balance the benefits and risks for your specific situation.

Common diseases related to it

• Intracranial (brain) aneurysm
• Ischemic stroke due to large-vessel occlusion
• Transient ischemic attack (TIA)
• Intracranial arterial stenosis (narrowing of brain arteries)
• Subarachnoid hemorrhage (often related to aneurysm rupture)
• Arteriovenous malformation (AVM)
• Dural arteriovenous fistula (DAVF)
• Arterial dissection (carotid or vertebral artery dissection)
• Cerebral vasculitis (inflammation of brain blood vessels)
• Venous sinus thrombosis (in selected protocols; sometimes evaluated with CT venography)
• Vascular complications related to brain tumors (assessment of tumor blood supply and vessel involvement in certain cases)

Health goals where it may help

• Rapid evaluation of stroke symptoms to support timely treatment decisions and protect brain function
• Identifying or ruling out a brain aneurysm to reduce the risk of life-threatening bleeding
• Assessing and monitoring the brain blood supply in people with known vascular disease or prior stroke/TIA
• Guiding treatment planning for AVMs, fistulas, or other vessel abnormalities
• Checking for causes of severe headache or neurological symptoms when a blood vessel problem is suspected
• Supporting surgical or endovascular planning by mapping brain arteries (a noninvasive “brain angiogram” approach)