Computed Tomography (CT) Scan

Computed Tomography (CT) scan is a special examination using a combination of X-rays and computer technology to produce cross-sectional images of the body, giving detailed information for diagnosis. We hope the following information will help you understand the procedure better and make your visit to the Department of Diagnostic and Interventional Imaging a pleasant one.

What to expect during the examination?
During the CT examination, you will be comfortably positioned on a special scanning couch. You will not feel anything, except couch movement between scans. The radiographer will instruct you to hold your breath for ten to fifteen seconds while the scans are being taken

 In many cases, you will be given an injection of contrast medium (X-ray dye), usually in the arm. This contrast medium goes into your blood system and outlines your blood vessels, improving the visualisation of certain structures. The contrast may make you feel warm for a few seconds. It will be passed out in the urine in 15 to 30 minutes.

If you feel any discomfort or pain during the injection, please inform the attending staff.

How high is the radiation dose?
The radiation dose you will receive is the smallest possible. As such, there are no demonstrable side effects from the radiation. If you have any concerns, please discuss it with the radiologist.

Will I need to be admitted?
The examination does not require hospital admission. It can be performed on an outpatient basis. If you are admitted to the hospital on the appointment day, please inform the ward staff to contact the Department of Diagnostic and Interventional Imaging about your scan.

Important points to note:

1. The examination time may vary from 15 to 30 minutes. This does not include the preparation time that could take up to 90 minutes for a pelvic scan.
2. When you are making the CT scan appointment, please inform us if you have any of the following conditions:
   1. allergy to contrast medium (from previous scan)
      
   2. asthma
      
   3. diabetes
   4. kidney (renal) disease
   5. had kidney surgery
      
   6. protein in your urine (proteinuria)
      
   
   For conditions related to kidney & diabetes, please tell us your latest creatinine level (umol/L) and the test date. If your creatinine level is abnormal, a blood test may be repeated on the day of appointment. It will take one hour for the blood result to be known. If the repeated result is still abnormal, your appointment may be cancelled or rescheduled or alternative examination may be suggested. This is a safety precaution to protect the kidneys.
   
3. If you are or suspect that you are pregnant, please inform the doctor, radiographer or reception staff before the scan.
4. Please do not carry any valuables, jewellery or excessive cash with you during your appointment.
   

Are there any special preparations for CT scan (without general anaesthesia or sedation and above 6 year-old)?
The preparation varies for different body parts.

You should avoid taking heavy meal. You can take light meal such as porridge or noodle soup in small portion. You may drink plain water anytime. Please arrive at the Department of Diagnostic and Interventional Imaging at least one hour before the appointment for registration and preparation.

For CT scan of the pelvis, a small amount of contrast medium may also be administered into your rectum to study the large intestines. Do not empty your bladder half an hour before the scan. If you are an inpatient and are on a urinary catheter, the nurse will be instructed to clamp it before the scan.

For CT, Angiography and child below six year-old, fasting for three to four hours is necessary, in preparation for intravenous contrast if needed.

For CT Colonoscopy, please refer to CT Colonoscopy brochure for the preparation.

Where necessary, a needle will be inserted into your vein for the administration of the contrast medium (X-ray dye ) or the medication for general anaesthesia or sedation.

What preparations are needed if I require sedation or general anaesthesia?
Fasting is compulsory for patient safety. For sedation, fasting of at least three hours is required. For general anaesthesia, fasting of at least six hours is required.

The last meal before the fast for either sedation or general anaesthesia should be light, comprising one cup of milk and two pieces of plain bread or biscuit. A heavy, oily meal can cause vomiting and severe complications.

Our nurse will call the patient, parent or guardian to advise on the fasting requirements.

Written consent for sedation or general anaesthesia is required. For patients below 21 years old, a parent or a legal guardian must give consent before we proceed. Hence, a parent or legal guardian must accompany the patient on the appointment day.

If your child is not well before the procedure, please call to inform us. We will decide whether patient is fi t for sedation.

*Do note that an Excuse Sheet will be given upon request. Medical Certifi cate (MC) will only be issued for this procedure that is performed under general anaesthesia.