WHAT DOES COMPUTED TOMOGRAPHY MEAN?

Computed tomography scans are often referred to as CT or CAT scans. It’s a type of medical imaging that uses ionizing electromagnetic radiation in the form of X-ray photons (energy) to create images of your body.

Conventional X-ray imaging uses a fixed X-ray source, which emits photons that travel through the body part of interest. An X-ray detector is placed behind the area of interest to record the signal of the photons after their journey, resulting in a two-dimensional image.

During a CT scan, a rotating X-ray source emits a narrow beam of photons through the body part of interest which is then recorded by an advanced detector on the other side. This results in a volumetric dataset that the computer reconstructs into numerous cross-sectional images, called tomographic images or slices. This creates three-dimensional (3D) images that can be viewed from multiple directions.

Since its invention by Godfrey N. Hounsfield at Electric and Musical Industries (EMI) in 1971, CT has proven to be a sophisticated type of medical imaging that provides detailed anatomic images of the body. It also has the ability to evaluate the arteries, veins, and blood flow to organs when augmented with intravenous contrast.

WHAT CAN A CT SCAN HELP DIAGNOSE?

CT scans are very good at imaging bone but can also provide detailed information about soft tissues in the chest, abdomen, and pelvis, in addition to blood vessels. A CT may be preferred to evaluate fractures or look for cancers or blood clots.

CT lung screening utilizes a lower radiation dose technique that can help to determine the presence of, and then further evaluate, suspicious lung nodules for lung cancer, as well as other serious illnesses. It could be appropriate for patients at high risk of lung cancer due to smoking, exposure to radon gas, a family or personal history of lung cancer, or other risk factors. In these cases, CT lung screening can help detect early forms of lung cancer, as small as a few millimeters in size.

For those at risk of coronary artery disease, a coronary CT angiography can be used to non-invasively examine the coronary arteries. It can detect both calcified or hard plaques and noncalcified or soft plaques, both of which have been implicated in adverse cardiac events. The presence of soft plaques is often best determined by IV contrast enhanced CT angiography.

CT virtual colonscopy utilizes a lower radiation dose technique to screen the large intestine (colon) and rectum for colon cancer. This requires insufflation of the colon with CO2 gas to permit better visualization. This differs from a colonoscopy in that an endoscope is not used.

HOW DO I GET CT IMAGING?

At Mayfair Diagnostics we provide CT lung screening, CT coronary angiography, and CT virtual colonoscopy as private pay examinations at our Mayfair Place location. They can be purchased for single or multiple body areas. We also offer Health Assessment packages, which provide a discount on multiple imaging exams when purchased together.

Your health spending account or group medical insurance plan may cover the cost of a private CT that is prescribed by a qualified health care practitioner. You will need to check with your plan administrator for coverage details.

Whether public or private, a CT must be requested by a health care practitioner. To determine whether a CT is recommended, you will need to discuss with your doctor your medical and family history, risk factors, and if there are symptoms, how long symptoms have been present and how they affect daily activities.

If a private CT scan is indicated as a best next course of action, a requisition will be provided, and the appointment can be booked. It’s important to note that the exposure to radiation from a CT scan is higher than that of a conventional X-ray, as it is a more advanced imaging modality, but the associated risk is still small. For example, the radiation exposure from one low-dose CT scan of the chest is less than the exposure from the earth’s natural background radiation over six months. In most cases, the benefits of a CT, such as the early detection of a serious illness, outweigh the potential health risk from receiving a higher radiation dose.

For more information, please visit our services page.

REFERENCES

Alberta Health Services (2022) “New screening program will use CT scans to detect early-stage lung cancer.” screeningforlife.ca/lung. Accessed August 26, 2024.

Canadian Cancer Society (2024) “Colorectal cancer statistics.” cancer.ca. Accessed August 26, 2024.

Canadian Cancer Society (2024) “Risk factors for colorectal cancer.” cancer.ca. Accessed August 26, 2024.

Diagnostic Imaging, Alberta Health Services (2021) “Computed tomography (CT).” myhealth.alberta.ca. Accessed August 26, 2024.

De Koning, H. J., et al. (2020) “Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial.” New England Journal of Medicine, 2020; 382:503-513. Accessed August 26, 2024.

National Institute of Biomedical Imaging and Bioengineering (2022) “Computed Tomography (CT).” nibib.nik.gov. Accessed August 26, 2024.

Schulz, R. A., et al. (2021) “How CT happened: the early development of medical computed tomography.” Journal of Medical Imaging. 2021 Sep; 8(5): 052110. Accessed August 26, 2024.