CT scan

A CT scan uses X-rays to take detailed images of the inside of your body. An X-ray camera rotates around you, capturing images from multiple angles. These 'slices' are then processed by a computer to create cross-sectional views – like slices through your body. They can also be combined to form a 3D image.

Because CT scans give very detailed internal images, they help doctors detect things that may not be seen on regular X-rays. They're often used in emergency situations – such as after an accident – to quickly check for internal injuries or broken bones. CT scans are also commonly used to diagnose or monitor ongoing health conditions such as cancer, heart disease or infections.

CT scans are usually done in hospitals or specialised radiology clinics. A mobile unit is now available in Aotearoa New Zealand. Read more about the mobile PET-CT scanner(external link).

• A radiographer is a trained medical imaging professional who will carry out your scan and support you during the procedure. 
• A radiologist is a doctor who specialises in interpreting medical images. They will review your scan and provide a report to your healthcare team.

Video: What to expect – CT scan

Your healthcare provider may ask for a CT scan to help: 

• identify the cause of symptoms such as pain, weight loss or a lump 
• check for injuries, broken bones or joint problems
• monitor conditions such as cancer, heart disease or infection
• examine organs such as your liver, bladder, kidneys or gallbladder
• assess blood vessels or check for blood clots 
• find internal bleeding
• guide procedures such as biopsies or pain relief injections. 

Preparation depends on the reason for your scan. You may be asked to:

• stop eating for 2 hours beforehand
• drink water or a special solution before your scan
• wear a patient gown
• remove jewellery, piercings, dentures, or glasses
• have a blood test to check your kidney function
• complete a health questionnaire to check for allergies or other conditions.

CT scans are quick – the actual scanning process usually takes just a few seconds to a few minutes.

• You’ll lie on a scanning bed that moves through a large, ring-shaped scanner.
• If contrast dye is needed, it may be given as a drink, an injection, or both.
• If contrast is used, your appointment may take up to 30 minutes.
• If no contrast is required, your scan will usually be completed in under 15 minutes.
  
  

During your scan

• Stay as still as possible to make sure they get clear images.
• You may be asked to hold your breath for short periods.
• You’ll be in constant contact with the radiology staff. Even if they’re in the control room, they can see and hear you at all times.
• The scan is painless, and your radiographer will guide you throughout.
• The scanner is quiet (unlike an MRI), although you may hear a soft whirring noise.

In some cases, your doctor may need a clearer view of certain parts of your body. To achieve this, you may be given a contrast dye – a special solution that helps highlight specific areas in your scan.

Most commonly, contrast is given as an injection into a vein in your arm using a small needle.

You may get:

• a warm sensation throughout your body
• a metallic taste in your mouth
• a brief feeling in your bladder, like you need to urinate

These sensations are normal and go away quickly.

Sometimes, you may also be asked to drink a contrast solution shortly before the scan so that your stomach and bowel can be seen more clearly.

Are there any risks with contrast dye?

Please inform the staff if:

• you’ve had a previous reaction to contrast dye
• you have any kidney problems.

Important notes

• Most people tolerate contrast dye without issues.
• A few people may have mild reactions such as a rash or itching, which can be treated with antihistamines.
• Serious reactions are rare, but your CT team is fully trained to respond if needed
• A simple blood test may be done beforehand to check how well your kidneys are working.
• If your kidneys aren’t functioning properly, the scan may be delayed or a different type of imaging may be recommended.

• You can get back to your normal activities straight after the scan
• If you received contrast dye, you may be asked to stay for a short time afterwards to make sure you're feeling well.
• It's good to drink extra water to help flush the dye from your system.

A radiologist will review your images and send a detailed report to your healthcare provider. They will then discuss the results with you.