Computed Tomography Scans: What are CT Scans and How do they Work?

Computed Tomography (CT or CAT) scans are commonly used to identify organs, disease, and abnormalities in patients’ bodies. The procedure is non-invasive and greatly reduces the need for exploratory surgery, if not omitting the need altogether.

CT scans are computerized x-ray imaging procedures used to generate cross-sectional images of the body. A beam of x-rays is aimed at the patient and rotated around the body to generate individual ‘slices’, which are called tomographic images.

These tomographic images contain more detailed information than conventional x-rays because they gather detail from multiple angles, not just one. These images can therefore be ‘stacked’ in order to form a three-dimensional image of the patient. Physicians can then analyze these images and provide more accurate assessments and identifications of any abnormalities.

How do CT Scans Work?

A CT scanner has two main parts: the Gantry, which is the x-ray scanner, and commonly referred to as the ‘donut’ due to its shape; and the bed which the patient lays on.

The x-ray scanner is contained within the Gantry, and rotates out of sight during the procedure. The bed slowly moves through the gantry during the procedure, while the scanner shoots narrow x-ray beams into the patient. Opposite the scanner is the detector, which records the images.

To the patient, it might seem like nothing is happening at all! In actuality, though, the scanner collects images of the area, records them, and stores them in digital format. The detail of the tissue thickness depends on the type of scan, as well as the type of scanner.

Once the CT scan is completed, the image slices can be viewed in two ways. Since they were collected individually, they can be viewed like slides. The computer can also compile all the gathered information, and generate a 3D image. The 3D image is extremely comprehensive, and can be rotated for in-depth analysis of the problem area.

For some procedures, especially intestinal and circulatory scans, the patient will need to take a contrast agent for the most accurate scans. Bone and other dense structures within the body are easily imaged with the CT scanner’s x-rays; however, soft tissue does not appear as readily without the use of a contrast agent.

Contrast agents are substances which are administered to a patient orally or intravenously, and which x-rays cannot penetrate as easily. As such, an organ containing a contrast agent will allow a CT scanner to retrieve an accurate image of the area in question. Iodine solutions may be injected to a person’s blood veins for circulatory scans, while barium-based solutions may be ingested for intestinal or other internal scans.

How Risky are CT Scans?

While the dosage for each individual varies depending on size, age, and the part of the body to be scanned, Computed Tomography scanners emit a higher amount of ionized radiation than the average x-ray machine. This is necessary in order to obtain high-quality imagery.

Ionizing radiation can cause adverse biological effects, notably the possibility for an increased risk of cancer. However, there is no solid data that links CT scanners to an increased cancer risk.

It is extremely risky to have a CT scan if you are pregnant or think you may be pregnant, as the x-ray radiation can cause significant damage to an unborn fetus.

Allergic reactions are also possible with the contrast agents used in certain scans. While infrequent, these reactions may include hives, redness, and itchiness. There are rarely life-threatening allergic reactions to contrast agents.

What are CT Scans Used to Analyze?

CT scans have been used for decades to detect, identify, and analyze countless internal problems. Consult with your primary physician to determine if a CT scan is right for you. Some of the common applications are:

• Head and Brain
• Sinuses
• Chest
• Abdomen and Pelvis
• Bones and spine
• Joints
• Calcium Evaluation
• Perfusions
• Blood vessels and blockages
• Surgical planning, treatment, and reconstruction

As the technology advances, and sensors and computers alike become more sophisticated, CT scans will be used for many more purposes in the future.  Florida Medical Clinic Orlando Health uses 2 state of the art, helical, CT scanners, a 16 row and a 64 row scanner. This provides a more detailed image for our radiologists to interpret.