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Computed tomography (CT)

A CT (Computed Tomography) Scan examination is an x-ray procedure performed using a computerised x-ray scanner that resembles a “doughnut”. Images are produced using a narrow beam of x-rays that are rotated around the region of your body to be examined. You will be asked to lie down on the CT scan table. During the CT procedure, the CT scan table will move in and out of the scanner several times to capture images of your body.

Some of the specialised CT scan examinations performed in SGH include:

  • CT Colonoscopy
    It is also called virtual colonoscopy (VC). This is a procedure which utilises x-ray to obtain 2D and 3D images of the inflated large intestines and rectum. Using carbon dioxide gas for inflation, it reduces abdominal discomfort for the patient so that the procedure is better tolerated. It is used to diagnose colon and bowel disorders.
  • CT Coronary Angiography
    This is a type of imaging used to visualize the blood vessels and other structures of the heart. It is used to check for the narrowing of the arteries and other heart conditions.
  • CT Liver Volumetry
    This is a procedure where the acquired liver images are used to obtain accurate measurements of the liver volume. This information acquired will be useful for liver resection and transplantation procedures.
  • CT Surgical Planning
    CT scan is performed for almost any pre or post-surgical planning procedures that requires evaluation of complex human anatomy as it is able to provide accurate and specific measurements. Some examples of such scans are CT Image Guided Surgery (IGS) Navigation, CT Makoplasty, CT Angiography of the Deep Inferior Epigastric Perforators, CT 3D Printing, just to name a few. 

Things to note on the day of appointment

Please refer to the Patient Preparation page for more information.

How to prepare for a CT Scan examination?

Depending on the CT procedure, you may be asked to fast - meaning not taking any solid food 4 hours before the scan. Fluids is allowed. For a detailed list on the types of CT procedures that requires fasting, please refer to Patient Preparation page.

For CT procedure that includes your pelvis or bladder, do not empty your bladder at least 1 hour before the scan. If you are on a diabetic medication called Metformin (Glucophage), please do not take it on the day of scan. Resume Metformin (Glucophage) 48 hours after your CT procedure.

What happens during a CT Scan examination?

You will be asked to lie on the CT scan table with the part of your body that needs to be scanned placed within the scanner. A gentle humming sound that is produced by the scanner may be heard. However, no moving parts of the scanner will touch you.

During the scan, our CT radiographers will be able to see and hear you at all times through a 2-way intercom. It is important to stay still during the scan in order to allow us to obtain the clearest images for you. A typical CT procedure usually takes between 15 to 20 minutes to complete.

Due to the nature of our work, we have to give priority to emergency cases, and may not be able to keep strictly to schedule. If you have any questions about the examination, do not hesitate to approach the staff attending to you.

What happens after the CT Scan examination?

If you have received contrast injection, please approach the nurse to have the intravenous plug removed before changing out of the hospital gown. Do continue to drink plenty of fluids for the next 8-10 hours to facilitate passing out of the contrast material. The contrast injected is colourless and should not affect the colour of your urine. After the CT procedure, you can resume your diet and all regular activities. For nursing mothers, you should wait for 24 hours after contrast injection before resuming breast feeding.

Our radiologists will read and report your CT scan images. A report will then be sent to your referring clinician electronically, who will then discuss the scan results with you at your next appointment in the clinic. 

What are the possible risks and limitations for a CT scan examination?

A CT procedure involves exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis usually outweighs the risk.

The risk of developing serious allergic reaction to the contrast material is rare and all necessary precautions will be taken to minimize such occurrence.
For patients undergoing CT scan examination that requires contrast material to be injected into a vein in your arm, there is a small chance of the injection leaking out from the vein and into the tissues under the skin. This is known as contrast extravasation. Stinging sensation, painful, tightness and swelling around the injection site area are some of the common symptoms you would feel. The trained radiographers will attend to you shortly. In severe situation, plastic surgery team will be called to examine your arm and provide further advice and treatment at your own cost, if necessary.

CT imaging is generally avoided in pregnant women.