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Computed Tomography (CT) Scanner

The scanner itself is a machine with a circular hole in the centre – it is often described as looking a like a polo mint.


You will be asked to lie on the table which will be raised to allow it to move through the hole during the scan. 

The images are taken by a rotating X-ray tube and are processed by a computer.

The resulting pictures show the area under examination in cross sectional slices. 

Your scan

CT scanning is totally painless. The only thing you will notice is the sound of the scanner and the slight movement of the table as your scan is taken. This can take between 5 and 20 minutes but you may need to spend longer than this in the department.

Sometimes it is necessary to gain more information from the scan by the use of a small injection into a vein in the arm or hand. There are few, or no, noticeable effects from the injection.  If this injection is given you will be asked to wait up to 30 minutes in the department after the scan has finished.

Extravasation (spillage of the x-ray dye) into the tissues under the skin is one of the complications of receiving contrast in CT.  However this is as low as 1.1%.  There is also the possibility of an allergic reaction to the contrast which is also very rare.

It is very important that you contact the department before your appointment if youtake Metformin or Glucophage or have Kidney Problems.

If you are pregnant

If you are, or might be pregnant it may not be possible to perform this scan.  Please telephone the number below for advice.

More information

If you have any queries about your scan please feel free to ask the radiographer when you arrive at the unit.  If you need to speak to someone prior to your visit please telephone 0151 556 3679

If you are taking medicine

Please continue to take any tablets or medicines prescribed by your doctor.  You may eat and drink normally before your scan unless advised otherwise, but please avoid alcohol.

If you are asthmatic & use an inhaler

Please bring your inhaler with you

If you require an ambulance

If you think you require an ambulance please notify us immediately – we might need to change your appointment time.

In most cases you will need to arrange your own ambulance on the numbers below

The ambulance service will ask you some questions to make sure the correct transport is selected for you

Telephone:                North West Ambulance                 0800 032 3240

                                Manchester ambulance                 0800 023 2292

                                Welsh Ambulance                         0300 123 2317

                                West Midlands (Cheshire)             0345 425 0050

After your scan

After your scan you will be able to return home.  It will be quite safe for you to drive or return to work if you wish.


  • Last Updated:
    01 October 2023
  • Review Date:
    01 October 2027
  • Author:
    KShannon / M Helsb
  • Summary:

    C.T. stands for Computed Tomography The scanner itself is a machine with a circular hole in the centre.

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