A computerised tomography scan (CT), or CAT scan, uses X-rays and a computer to create detailed images of the structures inside of the body. CT scans are normally done in the radiology department of a hospital by a trained radiographer.
CT scans are an important diagnostic tool. They can diagnose conditions such as cancer, stroke, blood clots, injuries and diseases of internal organs, problems with circulation and damage to bones. CT scans can be used to aid the treatment and diagnosis of certain conditions.CT scans are also used to assess the efficacy of your treatment and as part of your follow up after treatment or surgery.
Your doctor will only refer you for a CT scan when the benefits outweigh the risks. This is because you will be exposed to X-ray radiation, which can be harmful in high doses. Having an allergic reaction to the contrast medium (dye), although uncommon, is also possible.
When Are CT Scans Done?
The detailed images produced by CT scans have a number or useful applications. These include:
- Diagnosing medical conditions such as cancer, stroke, injuries to internal organs, and fractured bones.
- Guide further tests or treatments such as locating the exact location and size of tumours to aid radiotherapy or draining an abscess.
- Monitor conditions to check if treatment has been successful, such as the reduction of tumour size after cancer treatment.
Preparing For A CT Scan
You should notify the hospital before your appointment if you are diabetic or have any allergies, kidney problems, or if you are pregnant. Having a CT scan whilst pregnant is not advised.
Your appointment letter should mention everything you need to do to prepare for your scan.
Depending on the area of your body being scanned, you may be asked not to eat or drink anything for several hours before the scan. If you are having a CT scan of your colon (large bowel), you will usually be given a powerful laxative (colon cleanser) to completely empty your bowel before the scan.
Before having the scan, you may be given a special dye (called a contrast medium) to improve the quality of the images. This is normally injected into a blood vessel in your arm and should not be painful.
Before the scan begins, you will need to remove any metal items on your body, including jewellery. If you wear loose, comfortable clothes (without any metal parts) you may be able to wear these during the scan. If not, you may be provided with a hospital gown to wear.
You should let the radiographer know if you are feeling nervous about having the scan. You will usually be given a buzzer which can be pressed if you start to panic during the scan. If you are very anxious or claustrophobic, you may request a tranquiliser to help you relax.
What Happens During A CT Scan?
A CT scanner is a large, doughnut-shaped machine with a short tunnel in the middle. The scanning ring rotates around a small section of your body as you pass through the scanner. A CT scanner is not as claustrophobic as an MRI scanner, which surrounds your whole body.
You will be assisted to lie on a flat bed, on your back, before moving into the CT scanner. Straps and cushions may be used to help you maintain a still position throughout the scan. To ensure that images are not blurred, it is important to lie very still while the scan is in progress.
A radiographer operates the scanner from an adjacent room. The scan normally takes between 10 and 20 minutes.
Receiving Your CT Scan Results
You will not receive your report immediately after the CT scan. A radiologist needs time to analyse the information and images from your scan. Depending on your supplier (private or public), results can take a few days or a few weeks.
Your doctor or specialist will contact you if issues of concern are noted in the report.
Frequently Asked Questions
CT scans use low doses of radiation. More radiation is required to create CT scan images compared to a normal X-ray but this should not cause any long-term harm. Very high doses of radiation can potentially cause cancer.
Because radiation can be harmful to your baby, it is not advised to have a CT scan whilst pregnant.
If you struggle with anxiety or claustrophobia, your doctor might recommend a mild sedative, such as benzodiazepine, to help you stay relaxed during your medical imaging procedure.