Computed Tomography (CT)

CT is a special X-ray examination that is used to examine any area of the body. The CT machine is quite open and rarely considered claustrophobic. The scanner itself looks like a square donut. Unlike other X-ray examinations, the machine rotates around you collecting information that is then processed by a computer. The result is a series of pictures resembling slices through you.

You will be asked to lie on a table that moves through the centre of the scanner—you are not enclosed in anything. To prevent blurred or unreadable images you must keep still and will usually we asked to hold your breath for a few seconds at various stages of the scan.

The CT examination causes no pain or any kind of bodily sensation.

Your appointment

All the information regarding your CT scan appointment is detailed in your appointment letter. It is very important that you let us know as soon as possible if you cannot make the appointment by telephoning 020 3315 2059 from 9am–5pm, Mon–Fri.

Your appointment letter will contain information about your CT examination and will indicate whether or not you need to stop eating before you arrive for your scan. You may drink fluids such as water, tea and coffee and you should take all medications as normal.

If you are having your abdomen or pelvis scanned you may on arrival be asked to drink a quantity of water that is necessary to outline your stomach and intestines more clearly. Drinking the water will take between 30 and 60 minutes depending on the type of CT examination you are having.

Where to go

When you enter the front door of the hospital, take the escalator or lift to the first floor. Walk to the back of the building following the signs for the X-Ray Department. Once inside the X-Ray Department follow the signs to the CT/MRI/Ultrasound reception desk. You are advised not to take valuables with you when you attend your scan as the hospital cannot be responsible for them.

Will I need an injection?

It may be necessary for you to have a contrast injection (X-ray dye) to give a clearer picture for the radiologist to interpret. This usually involves putting a small needle into a vein in your elbow or hand through which the dye is injected.

When the dye is being injected you may experience a warm flush all over your body; you may get a metallic taste in your mouth; you may feel slightly sick; and sometime patients feel as if they are going to the toilet - you will NOT be, it is just a trick of the dye. Any such feelings will only last a few minutes and then pass. Many people feel nothing at all.

Are there any risks with the dye injection?

Yes, but they are very rare. Millions of X-ray dye injections for medical imaging examinations are performed in the UK and worldwide each year. Mild reactions such as nausea, vomiting and skin hives occur in 1–3% of patients. Severe reactions are very rare occurring in 1 out of 6,250 examinations. Fatal reactions may occur in 1 out of 100,000 patients. If you experience a delayed skin rash please contact us for advice.

Can I breastfeed after an injection?

Typically patients are advised to wait for 24–48 hours after receiving a CT contrast injection before breastfeeding again.

Can I bring someone into the scan room with me?

No—CT uses X-rays and only the person being scanned should be in the scanner room during the examination.

How long will the scan take?

The CT scan will last approximately 5–20 minutes depending on the area of the body being scanned.

Can I have a CT scan if I am pregnant?

Pregnant women should not have a CT examination or any X-ray examination. CT examinations are only performed on pregnant women in specific circumstances. If you are pregnant or think you might be pregnant, please inform the radiographer before you have your scan as there is a risk to the unborn fetus.

Are there any risks with this scan?

CT scanning uses X-rays to create the pictures. We are all exposed to background radiation each day of our lives. This comes from the ground and building materials, the air that we breathe, the food we eat and cosmic rays from outer space. Even flying in an aircraft increases our level of exposure. In the UK the largest contribution is from radon gas that seeps out of the ground and accumulates in out houses. This is normal and natural.

Each medical X-ray or nuclear medicine examination gives us a small, additional dose. The level of dose varies with the type of examination, ranging from the equivalent of a few days of natural background radiation to a few years. Low doses do not cause any immediate harmful effects but it is possible that there is a very slight increase in the chance of cancer occurring many years or even decades later. However we all have a 1 in 3 chance of getting cancer even if we never have an X-ray.

The radiation dose associated with a CT scan examination is slightly higher than other X-ray examination:

What happens next?

The CT images will be examined closely by a Radiologist. The report will be sent to the doctor who referred you for the scan and the result will then be discussed with you at your next clinic appointment. You will not be given the result on the day of the scan.