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This booklet has been written by the Lysholm Department of Neuroradiology at The National Hospital for Neurology and Neurosurgery (NHNN). The aim of the booklet is to provide information about an IV Dyna CT (Intravenous Dynamic Computed Tomography). 

It is intended for use by patients (or their families or carers) who have been referred to our service for this examination. It is not intended to replace discussion with your consultant. If you have any questions about this a member of the Neuroradiology team will be happy to answer them for you.

An IV Dyna CT is an examination performed to assess the major blood vessels within the brain. The information obtained from this scan can help to make a diagnosis, to plan your further treatment or follow up on previous treatment.

An IV Dyna CT is not performed with a CT scanner-as the title may suggest-but rather with a C-arm (picture 1). A C-arm is a type of x-ray machine used frequently during interventional procedures that acquire dynamic x-rays. The C-arm spins around the table producing x-rays while the contrast is being injected; this information is then collected by the computer where we can form a 3D image

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Picture 1: Siemens Bi-Plane C-Arm

 An IV Dyna CT can help give information about the major blood vessels in the brain. If you have had previous treatment involving a stent insertion or placement of metal coils into the blood vessels, it is helpful in visualising this. 

This type of examination may sometimes be used instead of a diagnostic angiogram, which is a more invasive procedure, usually requiring an admission including a short recovery time within the hospital.

All treatments and procedures have risks; we will talk to you individually about the risks of IV Dyna CT’s and the use of x-rays in your diagnosis and treatment plan. 

Problems that may happen straight away

Contrast agents are safe drugs; however as with all drugs, they have the potential to cause an allergic reaction. The department and team are well equipped to deal with reactions in the rare event of this happening. Please let us know if you are sensitive to iodine or allergic to contrast agents.

Problems that may happen later

Contrast agents may influence your renal function. If you know of any problems with your kidneys, please inform us as soon as possible so we can assess the safety of an injection of contrast for you. The risk of you having contrast will have been weighed against the benefit of having this procedure and is decided by the team referring you to Neuroradiology. For further information on the use of iodine-based contrast agents please see the information leaflet ‘Contrast Agents for X-ray, Fluoroscopy, CT and Angiography Examinations: An Information Guide’ or alternatively visit the trust website.

Problems that are rare, but serious

Whilst serious complications remain very unlikely, they may include:

  • Severe allergic reaction to contrast.
  • Radiation.

Radiation Risk

Like all x-ray machines, C-arm produces x-rays which can potentially be harmful and may cause some cancers to develop in the future.  Modern C-arm equipment and techniques are designed to keep the x-ray exposures as low as possible whilst producing some exceptionally clear images of your body. In addition, your doctor will have made a judgement about your risk and benefit before agreeing to the scan (including the risk to your health of not having the scan). The dose of radiation for each procedure can be compared to the amount of background radiation that you will receive just by living in the UK. The amount you receive will depend on the type of scan you are having.

Patients of childbearing capacity between the ages of 12 and 55 years are required by law to be asked about possible pregnancy when undergoing examinations involving x-ray. Patients who either are or think they may be pregnant must inform the Neuroradiology Department as soon as possible. In some urgent cases the scan may still go ahead but with additional precautions in place. To reduce the risk for early and unknown pregnancies, IV Dyna CT’s are usually performed within the first ten days of the menstrual cycle when pregnancy is much less likely.

The radiographer will discuss all possible risks with you and give you the opportunity to ask questions.

The decision whether to have this diagnostic examination is entirely yours. To decline the examination will not affect your personal care. However, it may mean that your consultant cannot be as certain or specific about effectiveness of previous treatment or any future treatment or procedures and it may affect some clinical decision making.

Your referring consultant will discuss alternative investigations with you, including their risks and benefits. These may include a MRI scan.

It is important that you are involved in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent. This confirms that you agree to have the examination and understand what it involves. Staff will explain all the risks, benefits, and alternatives. If you are unsure about any aspect of your proposed treatment, please don’t hesitate to speak with a senior member of staff.

You will be asked to arrive shortly before your examination. During this time, we will put a cannula (a small plastic tube) in the vein in your hand or arm, ready for the scan. We will also ask you some questions and/ or review your medical records to ensure it is safe to give you contrast.

Eating and drinking guidance

  • Gently increase your intake of fluids starting the day before your scan and continuing for another 24 hours after the scan to ensure you are well hydrated.
  • You may eat and drink as normal on the day of your examination.

Medication Guidance

  • Please contact us if you take metformin.
  • Take other medications as normal, before and after contrast, unless advised otherwise.
  • Contact Neuroradiology if you are unsure about any of your medications.

During your IV Dyna CT you will be asked to lie on the examination table on your back and remain still throughout the scan to allow for the best images to be obtained.

The c-arm will rotate around you in a few successions, first for planning your scan and then secondly, when the main scan is taking place. Lastly, it will return to its original start position.

During your examination an iodine-based contrast agent is injected through your cannula which will enable the blood vessels to be seen when X-rays are taken. The contrast agent will be injected, via an injection pump, at the same time as the scan so it is important to remain very still. You may notice a warm flush all over your body at the time of your injection, alongside a metallic taste in your mouth. This is completely normal.

A radiographer will be present in the room for the duration of your scan to reassure you and keep you informed.

After the examination you may be asked to wait in the department for up to 30 minutes to ensure you are feeling okay before you leave. After this time, we will remove the cannula and you will be able to go home. You can resume normal day-to-day activities after the scan.

A neuroradiologist will write review your scan and send a report to your referring doctor. They will discuss the test results with you at your next consultation.

The Brain & Spine Foundation UK

0808 808 1000 

UCLH cannot accept responsibility for information provided by other organisations.

Lysholm Department of Neuroradiology

National Hospital of Neurology and Neurosurgery

Queen Square




Direct line: 020 344 83444

Switchboard: 0845 155 5000 / 020 3456 7890

Extension: 83444 / 83440

Fax: 020 344 84723



Neurovascular Clinical Nurse Specialists

National Hospital for Neurology and Neurosurgery

Queen Square



Direct line: 020 344 83523

Switchboard: 0845 155 5000

Extension: 83523 



The Lysholm Department of Neuroradiology reception is located in Chandler wing, on the lower ground floor of the National Hospital for Neurology & Neurosurgery, Queen Square.

Please turn left when you exit the chandler wing lifts on the lower ground floor to find our main departmental reception.

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Page last updated: 07 May 2024

Review due: 01 May 2026