CT Perfusion

What is CT perfusion?

Perfusion CT is an X ray examination that looks at blood flow and the amount of blood within the brain. This can be combined successfully with acetazolamide (a diuretic medication, sometimes known as water tablets) to assess the blood flow of the brain more completely than any other methods mentioned below. Also information can be obtained about the blood vessels in the brain from this examination.

What is Acetazolamide?

Acetazolamide is a diuretic medicine that enters the blood circulation in the brain slowly and dilates the blood vessels in the brain. One of its actions is to increase the blood flow to the brain. Although it is used in hospital to treat other conditions, Acetazolamide is not licensed for this particular test. However, we have been doing this test at the Walton Centre for over 10 years without any serious side-effects. Acetazolamide is safe to administer and is generally well tolerated. Most common side effects can include a short spell of numbness around the mouth, pins and needles, tiredness and headache.

Why do I need a CT perfusion?

We all have an increased blood flow to the brain that we can call on if needed, this is called the cerebrovascular reserve. There is a suggestion that there may be a problem with your cerebrovascular reserve and a CT perfusion can help to identify this.

Who has made the decision?

The consultant in charge of your case will have referred you on to the radiologist carrying out the CT perfusion study. If after discussion with the radiologist you decide you do not want the test you can always opt out.

What are the alternatives?

There are other imaging examinations that can be used and they include PET, single-photon emission CT (SPECT), Xe-CT, dynamic, perfusion CT (PCT), MR , arterial spin-labelling (ASL), and Doppler sonography. Who will be performing the CT perfusion? The test is carried out by a radiologist (a doctor who specialises in x-ray procedures). The radiologist will meet you in the scanner and explain the test to you on the day of your scan, and answer any questions you may have. The x-ray equipment is operated by a radiographer. These members of staff will introduce themselves at the start of the examination. Occasionally student radiographers or medical students will be present to observe the procedure. 

Where will it take place?

In the CT scanner in the x-ray department.

How do I prepare for a CT perfusion?

If you have any allergies or if you have had a reaction to X ray dye previously, then you must let the doctor know.

Can I bring a friend or relative?

Yes, but for reasons of safety they will not be able to accompany you into the x-ray room.

What actually happens during a CT perfusion study?

You will be asked to lie on your back on the CT scanner table with two straps placed; one on the forehead and the other around the chin as it is vital that you remain still. The doctor will then put a small needle covered by a plastic tube into a vein in your arm. The needle will be removed and the plastic tube will be secured and remain in your arm during the procedure. You will then have an injection of X ray dye and saline. Following the injection, you will undergo a CT perfusion scan of your brain. The CT perfusion lasts for 60 seconds The radiologist will then inject 1g of Acetazolamide mixed with water. We must wait 17 minutes after the injection of Acetazolamide. During this period of 17 minutes it is very important to try and remain absolutely still. At the end of the 17 minutes a 2nd dose of X ray dye is injected and the CT perfusion is repeated.

Will it hurt?

Only the needle is likely to cause transient pain. The X ray dye can make you feel warm and give you a sensation of possibly wanting to pass urine.

How long will it take?

The test itself takes about 30 minutes.

What happens afterwards?

After the test we will ask you to wait in the department for another 30 minutes After this the radiologist will discharge you.

What will happen to the results?

A report of the procedure will be sent to your specialist.

Are there any risks or complications?

Any adverse reaction to this procedure is rare. This is a small possibility of an allergic reaction to the dye. If this occurs it will be immediate, but very rare