CT Scan
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Learn what to expect when visiting the Emergency Department. Learn More
Overview
A CT (Computed Tomography) scan uses X-rays to create detailed cross-sectional images of the body. It is fast, widely used in emergencies, and excellent at showing bones, lungs, stomach, intestines and acute internal bleeding. It is one of the most commonly performed diagnostic scans in any hospital. At St. Stephen’s Hospital, CT is available for both routine outpatient scans and inpatient and emergency cases — 24 hours a day, 7 days a week.
What is this test?
A CT scanner is a doughnut-shaped machine. You lie on a table that slides through the centre of the scanner while the X-ray tube rotates around you. A computer combines hundreds of images to produce detailed slices of the body. Unlike a plain X-ray, which shows one flat view, CT gives a 3D picture in slices. This makes it far more useful for complex problems — internal injuries, tumours, infections, and disease deep inside the body.
Why your doctor may order it
- Emergency assessment after head injury, accident, or chest pain
- Detecting stroke, brain bleeding, or skull fractures
- Investigating chest conditions — lung cancer, pneumonia, pulmonary embolism, COPD complications etc.
- Abdominal conditions — appendicitis, kidney stones, bowel perforation abdominal pain of unknown cause
- Guiding biopsies, drainage, and other procedures
- CT Angiography — to look at blood vessels in the heart, brain, lungs, or limbs
- Cancer staging — to see if cancer has spread
How long does it take?
The CT scan itself usually takes between 30 seconds and 7-8 minutes. Including registration, change and getting on and off the table, expect to be in the radiology department for about 20 to 30 minutes. In case of study in which you are required to the drink contrast orally at least 1 hour is required to drink the oral contrast before the scan. If contrast is given, allow an extra 15 to 30 minutes for the IV line and any delayed images.
How to prepare
- For contrast scans, fast for 4 to 6 hours before the test. Only few sips of water are usually fine. Kidney function test (BUN + Se creatinine ) is done for any contrast study. If deranged we do not give contrast.
- Tell the team if you have ever had a reaction to contrast dye, if you have kidney problems, or if you have asthma. Necessary pre-medication is given.
- Tell us if you are diabetic and on metformin — this medicine may need to be paused for 48 hours after a contrast CT.
- Tell the team if you are pregnant or might be — CT is usually avoided in pregnancy unless essential. Last menstrual period date is noted and if it is more than 10 drops before, pregnancy test is advised in young females to avoid exposure to radiation
- Wear loose, comfortable clothing with no metal. You may need to change into a gown.
- Bring your doctor's prescription, ID, previous reports or scans, and any old films.
What to expect during the test
You lie on the CT table — usually on your back. The technician moves you into position and steps into a control room. They can see, hear, and speak to you throughout. If contrast is needed, it is given before or during the scan. Oral contrast (a drink) may need to be taken over 30 to 60 minutes beforehand. IV contrast is given through a cannula and may cause a warm flush and a metallic taste in the mouth — both are normal and pass quickly. You will be asked to hold your breath for a few seconds during the scan. The machine is much more open than an MRI — most people find it less claustrophobic. The scan is silent compared to MRI.
After the test
- You can usually go home and resume normal activities right away.
- If contrast was used, drink extra water for the rest of the day to help your kidneys clear it.
- If you feel any rash, itching, or breathing difficulty after contrast, tell the team immediately — this can occasionally happen as a delayed reaction.
- Reports are usually available within 24-48 hours. Emergency scans are reported within an hour.
- Discuss the report with your treating doctor — they will explain what it means and what comes next.
Do's and Don'ts
- Arrive on time and follow the fasting instructions.
- Tell the team about all your medical conditions, allergies, and medications.
- Drink extra water for the rest of the day after a contrast scan.
- Remove jewellery and metal items before the scan.
- Bring previous scans and reports — they help the radiologist compare and interpret.
- Don't skip the fasting instructions for contrast scans — it can cause nausea or affect image quality.
- Don't hide a history of contrast allergy — there are alternatives we can use.
- CT scan is not done if you are pregnant unless it is extremely necessary and cannot be avoided. Scan is done often obtaining a written consent from the patient.
- Don't drive if you've been given any sedation.
- Don't ignore symptoms like rash, itching, or breathlessness after contrast — report them.
Understanding your results
A CT report describes what the radiologist saw, in technical language. The radiologist will compare your scan to your previous imaging when available — which is why bringing old scans matters. Findings are interpreted in light of your symptoms. An “unremarkable” scan means no significant abnormality. Specific findings — a kidney stone, a lung nodule, a small infarct — will be described and measured. Your doctor will explain what the findings mean for you, and whether anything further is needed.
Frequently asked questions
A single CT scan uses more radiation than a plain X-ray however the benefit of an accurate diagnosis almost always outweighs the small radiation risk. We avoid unnecessary scans, especially in children and we avoid doing scans for pregnant women.
Different tests for different problems. CT is faster, better for bone, lung, intestines and emergencies. MRI is better for soft tissue, brain, spinal cord, and joints & pelvic organs & breasts. Your doctor recommends the right one for your specific question.
It's a substance (usually iodine-based for CT) that highlights blood vessels and certain organs and any tumour on the scan. It is given through an IV, by mouth, or rectally. Most people have no problems with it; reactions are uncommon and we are equipped to manage them.
No. CT scan is much shorter and the machine is much more open, and quieter than MRI. Most people who find MRI difficult have no problem with a CT.
Yes, when necessary. We use lower radiation doses for children and only when the information cannot be obtained by ultrasound or MRI. We balance the small risk against the diagnostic benefit.