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.
CT scan images can provide much more information than do plain x-rays. They may be used to:
How you prepare for a CT scan depends on which part of your body is being scanned. You may be asked to:
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:
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.
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: ct@astraradiology.co.nz
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.
*Virtual Colonographies, CT Coronary Angiography and Coronary Artery Calcium Scoring are all done at the Ascot Hospital branch.
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.
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.
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.
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.
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.
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.
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.
A report will be given to your doctor. Your doctor will then recommend any follow-up treatment or action required.
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 ct@astraradiology.co.nz
Coronary Artery Calcium Scoring (Heartcheck) scans are done at our Ascot Hospital branch.
Virtual colonography is an advanced and highly accurate screening method used to detect colon cancer. Safer, quicker and less invasive than conventional colonoscopy, this technique uses a 60 second CT scan of the abdomen, along with 3D reconstructed images, to view the inside of the colon.
The radiologist analyses these images to identify the presence of polyps in the colon. Polyps are small growths that may become cancerous if they are not removed.
According to a recent study published in the New England Journal of Medicine, ‘…virtual colonography detected more than 90% of all significant polyps, performing slightly better than conventional colonoscopy.’
Virtual colonography is strictly a screening procedure.
Because of its non-invasive nature, it is not possible to take tissue samples or remove polyps during the procedure. If evidence of polyps is found, you will be referred for a conventional colonoscopy.
Risk factors for developing colon cancer include age (men and women over 50), a family history of cancer, a diet high in fat and low in fibre and physical inactivity.
A CT coronary angiogram is a CT scan of the arteries that supply your heart muscle with blood. At Astra Radiology, Auckland, CTCAs are done at our Ascot Hospital site.
Unlike a traditional coronary angiogram, CT angiograms don’t use a catheter threaded through your blood vessels to your heart. Instead, the CT scanner uses a combination of x-rays and high-powered computers to obtain cross-sectional images of your heart and heart vessels. These scans are becoming a common option for people with a variety of heart conditions. Early stages of coronary artery narrowing can be detected before any symptoms develop.
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