Finding the right tests…
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Finding the right tests…
CT Scan
CT angiography of the head, or CTA head, maps the blood vessels inside your brain using contrast dye injected into a vein in your arm. Doctors order it when an aneurysm, an arteriovenous malformation, or another vessel problem is suspected, often after a sudden, severe headache sometimes described as a thunderclap headache, or in the workup for a suspected bleed. The scan is timed so images are captured while contrast is actively flowing through your brain's arteries, which is what makes the vessels stand out clearly. Because iodine-based contrast goes into a vein, the centre will check your kidney function and ask about any past contrast reactions before the scan.
There's no single number from this scan. A radiologist examines the brain's arteries for narrowing, ballooning (an aneurysm), or abnormal tangles of vessels (a malformation), and describes their size, shape, and location in the report your doctor reviews. Follow-up scans, if needed, are compared against this first set of images to check for change over time.
CTA stands for CT angiography, a scan built specifically to show blood vessels rather than brain tissue. Contrast dye is injected into an arm vein, and the CT scanner is timed to capture images at the exact moment that dye is passing through the arteries in your brain.
- Aneurysms, which are weak, bulging spots in an artery wall that can rupture - Arteriovenous malformations, tangles of abnormal vessels that can bleed or disrupt blood flow - Narrowing or blockage inside the brain's own arteries
Because this scan relies on iodine-based contrast injected into a vein, the centre will ask about kidney disease, diabetes, and any past allergic reaction to contrast dye before your appointment. RadiologyInfo.org notes that people with severe kidney impairment need special consideration before receiving iodinated contrast, so tell your doctor about your kidney history in advance.
A plain head CT looks at brain tissue and bone. CTA head is built around the arteries themselves, timed to catch the contrast bolus as it moves through your brain's blood vessels, which a plain or even a delayed contrast scan won't capture in the same way.
CTA is timed precisely to catch contrast while it's actively moving through your brain's arteries, which is what makes blood vessels stand out. A general contrast head CT isn't timed the same way and focuses on brain tissue overall.
Many people feel a brief warm sensation or a metallic taste as the dye is injected. Tell the technologist if you feel itching, swelling, or trouble breathing afterward.
Often yes, especially if you have diabetes, kidney disease, or are older. The centre will let you know what's needed before your appointment.
Yes, CTA can detect unruptured aneurysms as well as ruptured ones, showing their size, shape, and location so your doctor can plan next steps.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
The scan itself is quick, often just a few minutes, though you'll also need time for the IV line to be placed and for contrast to be injected.
Tell the centre if you're pregnant or think you might be, since contrast and radiation exposure both need to be discussed with your doctor before a CTA scan.
In many cases, yes, since CTA is less invasive. Your doctor may still recommend a catheter-based angiogram if more detail or a treatment procedure is needed.