What Is a CT Scan and How Does It Work?

CT stands for Computed Tomography. It uses a rotating X-ray source and computer processing to create detailed cross-sectional images of the body. Doctors refer patients for CT when fast, clear anatomical detail is needed to diagnose or plan treatment.

How a CT scan works

You lie on a narrow table that moves through a short, doughnut-shaped scanner. An X-ray tube rotates around you and captures many thin slices from different angles. A computer reconstructs these slices into clear images that show bones, organs, and blood vessels. The scan is painless and typically takes 5 to 15 minutes of imaging time.

Common reasons your doctor might request CT

• Head injuries, severe headache, or suspected stroke
• Chest symptoms including suspected clots, infection, or tumours
• Abdominal pain, kidney stones, appendicitis, or bowel issues
• Trauma assessment for internal injury or bleeding
• Bone and spine problems including fractures
• Treatment planning and follow-up

Safety and radiation

CT uses ionising radiation. The dose is kept as low as reasonably achievable while still producing diagnostic images. For most patients the benefit of accurate diagnosis outweighs the small risk from radiation. Tell the team if you are or might be pregnant so we can plan safely.

Contrast dye

Some CT scans use an iodine-based contrast dye to highlight blood vessels and organs. It may be given through a small cannula in your arm. You could feel a brief warm sensation or a metallic taste, which passes quickly.

Please tell us if you have:

• Previous reaction to iodine contrast
• Kidney problems or are on dialysis
• Diabetes medication containing metformin
• Thyroid conditions
• Asthma or multiple severe allergies

How to prepare

• Bring your referral and Medicare card
• Wear comfortable clothing without metal; you may be asked to change into a gown
• Avoid food for 2 to 4 hours before contrast studies unless advised otherwise
• Sip water to stay hydrated
• Arrive 10 to 15 minutes early to complete a safety questionnaire
• Continue regular medicines unless instructed otherwise

What to expect on the day

1. Check in and complete a brief form
2. For contrast scans a radiographer places a small IV cannula
3. You lie still on the table; the scanner makes quiet whirring noises
4. You may be asked to hold your breath for a few seconds during images
5. Most exams finish within 10 to 20 minutes; you can usually go home right after

After your scan

• Drink water across the day, especially if you had contrast
• You can resume normal activities unless told otherwise
• Minor bruising at the IV site can occur; seek care if you notice swelling, pain that worsens, hives, or breathing difficulty

Results

A specialist radiologist interprets your images and sends a report to your referrer, usually within one to two business days. For urgent cases we contact your doctor on the same day.

CT vs MRI at a glance

• CT: uses X-rays, very fast, best for bone, lungs, trauma, bleeding, involves radiation
• MRI: uses magnet and radio waves, takes longer, best for soft tissue, brain detail, joints, no radiation

Book a CT scan

Have your referral ready and contact our team to schedule your appointment. We will confirm any preparation steps specific to your scan.