Computed tomography (CT) is one of the most widely used imaging studies after x-ray imaging and the two technologies use similar mechanisms when producing the images. However, the CT images are far more superior in terms of clarity and the descriptiveness while it is characterized by its ability to produce cross-sectional images as against the 2-dimensional (2D) projection image produced with x-ray technology.
X-ray technology and the necessity for CT imaging
In conventional x-ray imaging, radiation beams pass through regions of the body and gets absorbed by body tissues and organs to a varying degree as it passes through. The exiting radiation will react with a radiograph film placed behind the region of the body, which is being visualized, and will produce a 2D projection shadow of the region. Such images are valuable in recognizing distortions in the main body structures and contours as well as recognizing fluid collections, air collections and tissues changes that might have taken place as a result of various disease processes. However, the clarity and the descriptiveness of x-ray images could be rather low when it comes to detecting certain disease processes, localizing structural abnormalities and guiding treatment procedures, which require precise and accurate measuring. In such instances, clinicians will opt for a more advanced imaging technique and in most cases; CT imaging would be the first preference. However, there are instances in which the first choice imaging study would be CT imaging instead of x-rays and one such instance is when a person is suspected of having a brain hemorrhage.
Functioning of a CT machine
As mentioned earlier, the CT technology also depend on the variable absorption of radiation by different tissues and organs in the body although as the name implies, the outcome of CT imaging would be a ‘tomo graph’ [Latin term] or a ‘cross-sectional image’. It creates cross-sectional images of body regions by processing multiple radiographic images through specialized software. During the imaging process, the patient will be placed on a motorized table, which will move the patient into the CT machine through a tunnel like opening. As the patient moves in, a radiation source will rotate around the patient while detectors placed on the opposite side would be able to capture the penetrating radiation beams. The thickness of the radiation beam can be adjusted accordingly and could be synchronized with the movements of the table depending on the region to be imaged. As explained in the FDA website, a single rotation of the radiation source takes only 1 second and each phase of CT imaging would require around 50 to 60 rotations. Following obtaining multiple snapshots of the region, the computer software available within the system will process and generate a cross-sectional image of the studied region. In some instances, by administering intravenous contrast substances, it is possible to enhance the appearance of the CT image and better display the vascular structures present in the image.
Evolving CT technology
Although this is the most basic form of CT imaging, there are many additions made to the conventional CT imaging with the advent of sophisticated technology. Thus, the modern day CT machines are capable of producing high-resolution 3D and sometimes 4D images that would aid diagnostic and therapeutic processes much better than the conventional CT techniques.