A CT scan is also known as ‘CAT scan’ and ‘Computed Tomography.’ It uses radiation to analyse the body in 3D images.
CT scans are very good at showing bone, soft tissue, and blood vessels. While an MRI takes excellent pictures of soft tissue and blood vessels, a CT scan shows bone much better, so it's often used to image the spine and skull. It's also used to view the inner ear and sinuses because these areas are made of very fine bones.
A CT scan works similar to an X-ray. The body casts a "shadow" on film when it is exposed to the X-ray, much like when you hold a flashlight up to your hand and cast a shadow on a wall. All of the tissue that the X-ray passes through overlap on the image, making it hard to isolate different elements. A CT scan works around this limitation by capturing one narrow slice of your body at a time. Inside the CT machine, the x-ray tube circles around the patient taking pictures as it rotates. These slices can be viewed two-dimensionally or added back together to create a three-dimensional image of a body structure.
A dye (contrast agent) may be injected into your bloodstream to enhance certain body tissues. The dye contains iodine, a substance that X-rays cannot pass through. It circulates through the blood stream and is absorbed in certain tissues, which then stand out on the scan.
The radiographer carries out CT scans.
You will lie on the CT scanner couch. You should try to stay as still as possible so the machine can scan accurately. The table moves in/out of the scanner – it takes about 30 to 40 seconds – into and out of the scanner, which is the shape of a large doughnut.
To arrange get a CT scan, a you need a referral from your clinician. The department will contact you then to arrange a booking after the request has been discussed with a radiologist to agree the suitable scanning protocol. Waiting times vary by site and according to resources but are generally short.
The scanning does not hurt, but you may have a radiographer administer an injection with intravenous contrast liquid to help highlight certain areas in the imaging. After your scan you should drink a lot of water to flush out the contrast liquid.
CT scan results usually take up to 2 working days. It is then up to you to meet with your clinician to discuss the results. Doctors can see the scans and the written report.