CT scans

A CT scan, also called a CAT scan, is a radiological examination that uses X-rays to obtain detailed images of the inside of the body. 

Using the information collected, a computer then reconstructs an image in two or three dimensions. CT scans thus enable the detailed observation of organs, soft tissues, bones and blood vessels.

A cardiac CT scan, also called a coroscanner or coronary artery scanner, makes it possible to obtain thin cross-section images of the heart and its arteries. 

How does a CT scanner work?

A CT scanner is made up of a slip ring that has an X-ray tube on it, as well as digital detectors. This tube emits low-dose X-rays. The device measures the absorption of the emitted X-rays, and then it reconstructs an image of the body. In certain cases, a contrast agent is injected to make it easier to take measurements.  

A CT scanner differs from traditional X-rays in that it can provide images with a much higher resolution, and therefore a higher level of detail combined with images taken from different angles. This means that a CT scan can, in some cases, produce a three-dimensional representation of the area examined.

Why have a CT scan?

There are many reasons why a CT scan may be prescribed. It may be to detect infections or tumors, to assess bones or the brain, to visualize organs, to detect cerebrovascular accidents (strokes), etc. 

With specific regards to the heart, it can be used to examine the coronary arteries and to assess calcified plaque that may obstruct blood vessels and possibly cause a heart attack. This test also looks for birth defects or blood flow abnormalities in the heart vessels.

Unless otherwise advised by a physician, CT scans are contraindicated for pregnant women.  

What happens during a CT scan?

A CT scan is a painless examination that lasts several minutes.  

During a CT scan, the patient gets partially undressed and lies on an examination table that moves through a ring that emits X-rays. 

The patient must remain still, otherwise the images will be blurry. In some cases, the patient may need to hold their breath for a few seconds if asked by the radiologist in the adjacent room, who will communicate with the patient via loudspeakers.  

It may be necessary to inject a contrast agent. A nurse will then inset an IV line. Once again, this is not painful but the patient may experience a sensation of feeling warm. 

Once the examination is finished, the patient can leave. 

How to prepare for a CT scan

In general, a CT scan does not require any special preparation. Patients may be asked to not eat or drink for several hours before the scan. 

In all cases, the patient must not wear any metal objects (jewellery, glasses, etc.). 

The patient may be asked to wear a hospital gown.

If a contrast product must be injected, it is important to report any previous reactions to similar products beforehand. Sometimes, it will be necessary to do a blood test prior to the scan. This is to make sure that the kidneys are working properly, and that the contrast product will be correctly excreted from the body afterwards.

How is a CT scan interpreted? 

The CT scan can be read immediately with the radiologist. However, it may also take longer to interpret a CT scan, and in this case the doctor will contact the patient at a later time. In general, the printed images and the examination report are sent by regular mail. 

The radiologist will examine all of the image cross-sections, i.e. the image “slices” of the region examined. These images are usually shown in three dimensions and can be used to analyze the size, shape and exact location of any potential anomalies. The radiologist will then write a report that will be sent to the primary care physician.