CT angiography of the head – scan report

CT angiography of the head: a detailed map of the arteries in your brain

CT angiography of the head, also called a CTA head, CT angiogram of the brain or CT cerebral angiography, is a type of computed tomography (CT) scan that uses X-rays and a special iodine-based contrast material to produce detailed images of the blood vessels of the brain. The contrast is injected into a vein in your arm, and the scan is timed to start as it reaches the arteries inside the skull. Within a few seconds, a rotating X-ray tube captures hundreds of very thin slices, from which software can create cross-sections and three-dimensional images that the radiologist can view from any angle.

CTA is used to look for a bulge in an artery wall (aneurysm), a narrowed or blocked artery in a stroke, a tear in the wall of an artery (arterial dissection), an abnormal tangle of vessels called an arteriovenous malformation and other conditions that affect blood flow to the brain. Because the images can be obtained within minutes, it is also a standard part of emergency care for stroke and bleeding in the brain.

One study may contain over a thousand images. Spotting a 2 mm aneurysm on a branch of the middle cerebral artery, or telling it apart from a normal vessel loop, takes specialist training. At Eurodiagnosis, CT angiograms are reported by neuroradiologists, radiologists who specialise in diagnostic imaging of the brain, head and nervous system.

This page is written for patients and families who already have CT angiogram images and need an expert interpretation of them. Below, you will find how ordering works, what your report contains, when the scan is used and what happens during the examination.

How to order a report on your CT angiogram of the head

1. Pick your extras and pay. With the region preset, you only decide on extras: a comparison with an earlier scan of the same area and, if your doctors work in German or Italian, a translated report.
2. Tell the radiologist what you need answered. A specific question produces a sharper report: “Has my 4 mm aneurysm grown since last year?” helps more than “please review”. Mention your symptoms and relevant medical history and, for a second opinion, attach the report you already have.
3. Obtain the full image set. Your hospital or imaging provider will release the scan on request, usually on a CD or DVD (sometimes with 3D reconstructions) or through an image-sharing link. Ask for the complete DICOM study, thin-slice series included, because screenshots or a few 3D pictures do not allow a proper diagnostic assessment. After payment, a short guide shows you how to transfer the files.
4. Neuroradiology reading. Your angiogram goes to a specialist in neuroradiology, who reviews every series, builds extra reconstructions of the blood vessels where necessary and checks them against your question and any previous scans.
5. Receive your report. The 72-hour clock starts once your upload is complete, and no report takes longer than five working days. You will get a text message when yours is ready to download.

Why choose Eurodiagnosis for your CT angiogram report?

• A neuroradiologist, not an algorithm. Software helps to display the images, but every word of your report comes from a fully qualified, practising neuroradiologist: never from AI and never from a doctor in training.
• An independent, fresh read. For a second opinion, the radiologist forms a view from the images first and only then opens the earlier report, so a previous error is not simply carried over.
• Measurements instead of vague wording. Aneurysms are measured in millimetres, narrowings are graded as a percentage and every finding is linked to a named artery.
• Clear for you, useful for your consultant. The report uses the terminology your neurologist, neurosurgeon or stroke team works with, and its conclusion is phrased so that you can follow it too.
• Fully online. No referral letter, no appointment and no travel: you order, upload and download from wherever you are.

What does a CT angiogram of the brain show? The content of your CT scan report

Your report contains a complete assessment of the condition of the blood vessels of the brain. The radiologist traces the arteries from where they enter the skull out to their smaller branches over the surface of the brain, covering:

• the internal carotid arteries in the skull base, including calcified plaque in the carotid siphon,
• the circle of Willis, the ring of connected arteries at the base of the brain, and the anterior, middle and posterior cerebral arteries,
• the vertebral and basilar arteries, which supply the brainstem, the cerebellum, the back of the brain and the upper spinal cord,
• normal anatomical variants, recorded so that they are not later mistaken for disease,
• the brain and skull as visible on the source images, where a haematoma, swelling of the brain (oedema), a recent infarct, a mass or a skull fracture may also be found,
• technical quality: contrast timing, movement and artefacts due to aneurysm clips, coils or dental work, which may limit what can be seen.

When there is an abnormality, the report describes it precisely. For an aneurysm, that means its location, size in three dimensions, neck width, shape and the direction it points, plus any small secondary bulge (bleb) on its wall. A neurovascular team needs exactly these details to plan management, whether that means monitoring, endovascular coiling or surgical clipping. A narrowed artery is described by the degree and length of the stenosis, a blocked one by the site of the occlusion and how well collateral vessels fill the territory beyond it. For an arteriovenous malformation, the report covers the size of the nidus, its feeding arteries and how it drains.

How does a radiologist interpret a CT angiogram of the brain?

The radiologist works through the source images in multiple planes and builds additional views: maximum intensity projections showing a long stretch of a vessel in one image, curved reformats along winding arteries and 3D reconstructions of an aneurysm neck. If a non-contrast CT scan was performed first, both are read together. Instead of filling in a fixed template, the radiologist follows a structured checklist so that no vessel segment is skipped, then interprets the findings in the light of your symptoms and history.

The final section, the impression, is the part your consultant will read first. It answers your clinical question directly. Where the images genuinely leave more than one explanation open, the alternatives are listed from most to least likely. It also states whether anything further is advisable, such as a catheter angiogram, an MR angiogram, a repeat CT scan after a set interval or a referral to a neurovascular clinic. If you upload prior studies, the report includes references to them and describes any change between the examinations.

What does it mean if my CT angiography is normal?

A normal result is a clear statement in its own right, for example: “The intracranial arteries opacify normally. No aneurysm, vascular malformation, significant stenosis or occlusion.” It often allows your doctor to rule out the main vascular causes of your symptoms. However, CTA can miss very small aneurysms, especially those under 3 mm. When bleeding around the brain has been confirmed but the angiogram looks normal, specialists may therefore still recommend catheter angiography or a repeat study. Your report states whether such a limitation applies to you.

When is CT angiography of the head performed? What doctors look for

No CT scan, including a CT angiogram, is performed just in case. Under the UK’s Ionising Radiation (Medical Exposure) Regulations, an IR(ME)R practitioner must justify every exposure to X-ray radiation before it takes place. Your doctor may have requested a CTA head because of:

• a sudden, severe “thunderclap” headache, or a subarachnoid haemorrhage already seen on a plain CT scan, to look for a ruptured aneurysm,
• suspected acute ischaemic stroke, to detect a blocked large artery and decide whether the clot can be removed by thrombectomy (NICE recommends CT angiography for this, and in stroke the scan usually covers the neck as well),
• bleeding inside the brain in a younger person or in an unusual location, to identify an underlying aneurysm or malformation,
• a known aneurysm, which may have been found by chance on an earlier scan and now needs monitoring with CTA or checking after treatment,
• a higher risk of aneurysms, for example two or more affected first-degree relatives, or autosomal dominant polycystic kidney disease (ADPKD) with a family history of aneurysm (MR angiography is often preferred for screening, as it does not use X-ray radiation),
• concern about arterial dissection, inflammation of the vessels (vasculitis) or vessel spasm after a bleed; if the neck arteries also need checking, a head and neck CTA is performed,
• planning surgery for a tumour lying close to major blood vessels.

Non-contrast CT, CT with contrast or CT angiogram: what is the difference?

A non-contrast CT scan of the head is usually the first test in an emergency, as fresh blood shows up well without any injection. A standard contrast-enhanced CT of the head is acquired a little longer after the injection, once the contrast has had time to collect in abnormal tissue, which helps to show tumours, abscesses or inflammation. A CT angiogram is timed to the second for the arterial phase, uses much thinner slices and is reconstructed to display the blood vessels. Catheter angiography, also known as digital subtraction angiography (DSA), remains the most detailed test of the arteries. However, it is an invasive procedure: a thin tube is guided from the groin or wrist into the arteries of the neck. CTA provides most of this information without that risk and is therefore usually the first vascular test.

How is a CT angiogram of the head performed?

Apart from the cannula, the examination is painless. A radiographer inserts a small cannula into a vein in your arm and connects it to an injector pump, then helps you settle on the scanner table with your head in a cushioned rest. The CT scanner is a wide, short ring rather than a long tunnel, and mainly your head and neck pass through it. Often a non-contrast CT scan of the head is taken first. Then the contrast material is injected and the table glides through the ring while the scanner records the images.

How long does a CT angiogram take?

The angiographic acquisition takes only a few seconds, and you will be asked to keep still and not swallow during it. As the contrast circulates, many people notice warmth spreading through the body, a metallic taste or a feeling of having passed urine. These effects are normal and fade within a minute or two. Including preparation, the appointment usually lasts 20 to 30 minutes, and staff may ask you to wait a little afterwards before the cannula comes out. Drinking normally for the rest of the day helps your kidneys clear the contrast from the body.

Preparation, safety and contraindications

As with other imaging procedures that use contrast, follow the hospital’s instructions on eating and drinking, and tell the team in advance if any of the following applies to you:

• Kidney disease, diabetes or metformin. You may need a recent kidney function blood test (eGFR). Metformin usually has to be paused only if kidney function is markedly reduced or has recently worsened, but follow the advice you are given.
• A previous reaction to contrast. Staff will assess the risk and may choose a different agent, add precautions or suggest another type of imaging.
• An overactive thyroid. Iodine-based contrast is not normally given to people with untreated hyperthyroidism until it is under control, except in an emergency.
• Pregnancy or possible pregnancy. Say so before the cannula goes in. If the situation is not urgent, the team may postpone the scan or suggest MR angiography.
• Breastfeeding. Current UK guidance does not require you to stop breastfeeding after the injection.

Remove anything metal around your head, such as hair clips or earrings, because it creates streaks that can hide small vessels.

Counting natural sources and medical tests, the average person in the UK receives about 2.6 mSv of radiation a year. A head-only CT angiogram adds roughly 2 mSv, or about 3 to 4 mSv in total if a plain CT of the head is done first. Ordering a Eurodiagnosis report does not change that figure, because it is based entirely on the scan you already have.

Clear answers about the arteries of your brain

Phrases such as “small aneurysm cannot be excluded” or “possible stenosis” in an existing report often raise more questions than they answer. An independent reading by a neuroradiologist replaces vague wording with concrete statements wherever the images allow it: which artery is affected, how large the finding is, how significant it is likely to be and whether monitoring, treatment or further tests make sense. That clarity helps you prepare for the next conversation with your consultant and make decisions about your health with greater confidence.

Your CT angiogram, reported by a neuroradiologist: no waiting list, no referral, no clinic visit.

CT angiogram report: frequently asked questions