Computed Tomography (CT)

A CT scan uses x-rays and high-powered computers to obtain cross-sectional images of the body. At Astra Radiology, Auckland, we have CT scanners at four of our branches.

CT images show all types of tissue including lungs, brain, bone, muscles and abdominal organs with great clarity. CT scans are often used to guide fine needle biopsies, nerve root injections and other minimally invasive procedures.

  • Reasons for the procedure

    CT scan images can provide much more information than do plain x-rays. They may be used to:

    • Diagnose muscle and bone disorders, such as bone tumours and fractures.
    • Pinpoint the location of a tumour, infection or blood clot.
    • Guide procedures such as surgery, biopsy and radiation therapy.
    • Detect and monitor diseases and conditions such as cancer, heart disease, lung nodules, liver masses and kidney stones.
    • Detect internal injuries and internal bleeding after trauma.
    • Look at the coronary arteries and heart vessels (CT Coronary Angiography & CT Coronary Artery Calcium Scoring – also known as ‘HeartCheck’).
    • Construct a 3D image of the inside of the bowel (Virtual Colonography).
  • Before the procedure

    How you prepare for a CT scan depends on which part of your body is being scanned. You may be asked to:

    • change into a gown
    • remove any metal objects, such as a belt or jewellery
    • stop eating for a few hours before your scan.

    A special x-ray dye called contrast is needed for some CT scans to help visualise blood vessels, intestines or other structures. Contrast can be introduced to your body in a variety of ways:

    • Orally: if you are having an abdominal and/or pelvic scan, you may be asked to drink several glasses of liquid containing contrast before your scan. The contrast will highlight your bowel on the scans and differentiate it from other organs and soft tissues.
    • By injection: Contrast can be injected through a vein in your arm during the scan, to help visualize certain blood vessels. You may experience a feeling of warmth during the injection or a metallic taste in your mouth.

    Because CT scans use x-rays, women should always inform their doctor, or the radiographer prior to the scan, if they think they maybe pregnant, or if they are trying to become pregnant.

  • During the procedure

    • CT scanners are shaped like a large doughnut standing on its side.
    • You will be lying on a table that will move into the middle of the scanner just before the scan begins.
    • Straps and pillows may be used to help you stay in position.
    • The table will move slowly through the scanner during imaging.
    • If you need an injection of contrast, it will be administered while just prior to, and during, the scan.
    • You may be asked to hold your breath at certain points during the scan to avoid blurring the images.
    • Due to the advanced technology of modern CT scanners, the actual time you spend being scanned is very low. You may spend as little as 5 minutes on the CT table.
  • After the procedure

    • After the scan you can return to your normal routine.
    • If you were given an injection of contrast, you will be asked to wait for a short time before leaving the department.
    • You will be told to drink lots of fluid to help your kidneys flush the contrast material from your body.
    • Results from your CT scan will be sent to your referring doctor, usually 1 – 2 days, although this timeframe does depend on the type of CT scan you have had.
  • Risks of the procedure

    • Because CT scanning uses x-rays, you will be exposed to some radiation during the scan.
    • If you are pregnant or think you may be pregnant, you should not have a CT scan due to this radiation exposure.
  • To make an appointment

    For the majority of CT scans, we need to see your referral before booking you an appointment.

    Please email a copy of your referral to:

    Once the technicians have protocolled your referral and/or your ACC details have been checked, we will be in touch to discuss appointment times with you.

Find out more about the services we offer in this area

Please note; not all services are listed below, and not all services are available at every site

Coronary Artery Calcium Scoring (or ‘Heartcheck’) is a new test in the fight against New Zealand’s number one killer – heart disease. In less than 20 minutes we can calculate a score that indicates how likely you are to have symptoms of Coronary Artery Disease.

  • What is Coronary Artery Calcium Scoring?

    Coronary Artery Calcium Scoring (CACS) is a relatively new method to image the coronary arteries to look for signs of Coronary Artery Disease (CAD) due to the buildup of calcium in fatty deposits (or artherosclerosis, also called plaques) in the coronary arteries.

    This technique involves the use of a High-Speed Gated CT (Computerised Tomography) scanner. It does not require any medicines or x-ray dyes. ‘Gated’ refers to the ability of the CT scanner to take images in time with the heartbeat, so that there is no blurring of the image.

    With a few breath holds, images can be taken of the coronary arteries. From the images the amount of calcium in your coronary arteries is measured, and a score (CAC Score) is calculated from the amount of calcium present. The calcium score is then compared to a reference range for the population of your age and gender, and gives a relative risk of developing symptoms of coronary artery disease compared to that of the rest of the population.

    The Heartcheck scan doesn’t replace coronary angiography. The two tests provide different types of information.
    Heartcheck screening more accurately determines who is at risk of developing symptoms of coronary artery disease. Coronary angiography is for detection of narrowing of the coronary arteries in a person who already has symptoms of possible coronary artery disease.

    The Heartcheck scan can detect the development of plaque before symptoms occur. Plaque starts being deposited in the wall of the artery years before it narrows the artery to the point that symptoms develop. Detection of early coronary artery disease allows individuals to take modifying action before symptoms develop.

    Only 60% of people with heart disease have the traditional risk factors for coronary artery disease. CAD is a disease of genetics and lifestyle. You cannot be completely reassured that you will not have heart disease just because your cholesterol is normal, you don’t smoke, have a normal blood pressure and exercise regularly.

  • What is atherosclerosis?

    Atherosclerosis is the build up of fatty deposits in the lining of the arteries. This causes narrowings of the arteries, eventually to the point that blood flow is reduced, and leads to symptoms of coronary artery disease such as chest pain and breathlessness. Sometimes a blood clot may form on a fatty deposit, and cause the artery to block suddenly. This causes a heart attack, severe angina or even death. A heart attack is the largest single cause of death for men and women. Over 30% of those suffering a heart attack will die suddenly without warning.

    Atherosclerosis is treatable at any stage. The earlier the treatment is commenced the better. There are three objectives when managing atherosclerosis:

    • to reduce the progression of the disease

    • to stop the formation of new fatty plaques

    • to encourage regression of non-calcified plaques.

    Treatment involves intensive lifestyle modification with a healthy diet, exercise, weight loss if appropriate, drugs such as statins to reduce blood cholesterol levels, cessation of smoking, and reduction of blood pressure if required.

  • Who should have this test?

    The test is best suited to males aged 40-70, and females aged 50-70. Your doctor can assess your cardiac risk to some extent using tables from the National Heart Foundation. If you are at high risk on the NHF table, then the Heartcheck result will not change this and you probably will not benefit from having it done. If you are at intermediate risk on the NHF tables, then the Heartcheck test is very useful at determining whether you should take aggressive preventative action or whether you can be reassured, and is strongly recommended. If you are at low risk on the NHF tables, then the Heartcheck test result is usually the same and may not benefit you.

    However, there are exceptions to these general rules. For example, even if you appear to be at low risk on the NHF
    tables, if you have a close relative who develops cardiovascular disease (heart attack, stroke etc), then you may be at much higher risk than the NHF tables suggest, and a Heartcheck scan can confirm this and allow you to adopt preventative measures. Those who are at high risk on the NHF tables who are having trouble with side-effects of statin medication may find that a Heartcheck scan indicates they are at lower risk than previously thought, allowing them to stop taking medication unlikely to be of any benefit, or alternatively it may confirm that statin therapy is really necessary and should be continued if at all possible.

    If you already have cardiovascular disease such as angina, or have suffered a heart attack or stroke, then by definition you are at relatively high risk of disease, and the Heartcheck scan is not appropriate for you.

  • How often should I have this test done?

    As you get older your risk of developing cardiovascular disease changes, and you can develop high blood pressure and increased blood cholesterol levels. Therefore, even if your Heartcheck scan result shows you to be at low risk, it is worth repeating the scan in 5 years time.

  • How much does this test cost?

    Your GP can refer you for a Heartcheck scan. However, because it is a screening test, it may not be covered by your health insurer. For current pricing, please ask the booking specialist when making your appointment.

  • Before the procedure

    You must have a doctor’s referral to take this test. We do require some clinical details, for example your cholesterol levels, to ensure that we can interpret the scan most effectively.

    There is no other special preparation and any other instructions will be given to you when you make your appointment.

  • During the procedure

    • First you’ll be asked to fill out a brief questionnaire that incorporates information supplied by your doctor.
    • You will then be asked to lie in the CT scanner for the scan. ECG leads will be attached to your shoulders and stomach so the images can be timed with your heart beat.
    • You will be asked to hold your breath for only a few seconds. There is no need for medication of any sort, and you cannot feel the images being taken.
  • After the procedure

    A report will be given to your doctor. Your doctor will then recommend any follow-up treatment or action required.

  • To make an appointment

    You must have a GP or specialist referral for a Coronary Artery Calcium Scoring scan. Once you have your referral, please call us on (09) 520 9550 and select ‘CT’ from the menu, or email

  • Location

    Coronary Artery Calcium Scoring (Heartcheck) scans are done at our Ascot Hospital branch.

Make an appointment online or call our dedicated bookings line