Contents

Computational Tomography - What is it, Why Use It and How Do I Prepare for It?

What on EARTH is a CT Scan?

CT Staff with Patient
(Image taken from Amber Diagnostics Website, Published 2013/02/04, Accessed 2020/11/08)

A CT scan is a medical imaging technique that uses many different X-Ray images to create one image of the body. During a CT scan, you will lie on a bed that moves through an arc, called a gantry. As you move through the gantry, the scanner will emit a series of narrow beams. This is quite different from an X-Ray, which only sends one radiation beam. We do this so that we can obtain a much clearer image of the lungs. An image can then be projected onto the computer screen for examination. This is a quick and painless procedure which will be over in a matter of minutes.

How does COVID-19 present on a CT Scan?

We use CT scans in order to detect abnormalities in the lungs. The scans can detect hazy, patchy, white spots in the lungs - which are an indicator of COVID-19. The CT scan can create a 3D image of the lungs. In severe cases of COVID-19, as the pneumonia progresses, air sacs can become filled with fluid leaking from the blood vessels in the lungs. This is what we are looking for on a CT scan which can detect the presence as well as the severity of COVID-19.

Why do we use CT scans in relation to COVID-19?

Though, in theory, COVID-19 can be detected on a CT scan, it is currently diagnosed through a swab test – imaging is not recommended for patients with suspected COVID-19. However, CT imaging plays an important role in the disease for hospitalised patients who have further complications. In COVID-19 patients, CT imaging is used in extreme cases, most commonly to diagnose secondary infections such as pneumonia.

What are you even looking for?

Pneumonia, including COVID-19 pneumonia, increases density in areas of the lungs, which is what the chest CT is trying to detect. These are visible as areas of whiteness around the lungs as seen below.

CT Scans of Lungs with Pneumonia
(Image taken from News Medical Life Sciences Website, Published 2020/03/15, Accessed 2020/11/08)

What to Expect as a Patient Going into a CT Exam?

In preparing for the CT exam all artefacts are removed. You may be asked to change into a hospital gown and rehearse breath holds. The scan will take no longer than 10 minutes. As a patient, you must remain still throughout the scan and may be asked to hold your breath at various intervals. The CT exam will produce an excellent 3D projection with good visualisation of the lung tissue and any potential damage done to it as a result of coronavirus.

Radiation Dose to the Patient During a CT Examination

There’s no need to be afraid

Although the radiation dose for CT is classified as a high dose technique, it is relatively low in comparison to some everyday tasks and is equivalent to smoking 140 cigarettes, driving 6,000km in a car or flying 40,000km in a plane.

References Used:

Last updated on Nov 12, 2020