How do CT scans work? Understanding the intricacies of CT scan technology sheds light on its remarkable diagnostic capabilities and medical applications.
Computed tomography, commonly known as a CT scan, is a diagnostic imaging procedure that provides clear definition of bones, organs, and soft tissue in as little as 5 minutes. CT scans utilize an x-ray beam that revolves around the patient to collect cross-sectional image data that is reconstructed into image slices for analysis.
How Does A CT Scan Work?
During CT scans, the patient lies on a table that slides in and out of the CT scanner during imaging. The CT tube emits a focused beam of X-ray that revolves around the patient. The CT scanner images the body from every angle. As x-ray passes through the body, anatomical structures with higher density obstruct a greater percentage of x-ray from reaching the detector.
As the X-rays pass through the body, denser anatomical structures obstruct more of the X-rays, preventing them from reaching the detector.
Consequently, bone appears very bright on the CT images, various anatomical structures appear in shades of gray, and liquids and air show up as very dark areas.
The detector assembly, positioned opposite the X-ray tube, converts the captured image data into a high-speed fiber optic signal, which the CT scan computer processes.
Detector Assembly
This data is then reconstructed into 2D image slices and 3D renderings, allowing a radiologist to make an accurate diagnosis.
When examining CT scan images, bone will show up very bright. Anatomy will show up as varying shades of gray, while liquid and air will show up very dark. The detector assembly sits opposite the x-ray tube. It converts the image data to a high speed fiber optic signal for processing by the reconstruction computer. 2D image slices and 3D rendering enable accurate diagnosis by a radiologist.
The radiation exposure during a CT scan varies depending on the type of examination. For instance, a
How Much Radiation Is Used In A CT Scan?
An average chest CT scan exposes the patient to approximately 3.1 millisieverts (mSv) of radiation, which is about the same amount of background radiation an average person receives in a year. Brain CT scans exposes patients to about 1.8 mSv of radiation, while a whole-body CT scan can require exposure up to 20 mSv. However, the low-dose imaging techniques used during a CT scan ensure that patient exposure adheres to the ALARA (As Low As Reasonably Achievable) principle.
During the scan, a contrast agent may be administered to enhance the images. This contrast medium helps to differentiate blood vessels, organs, soft tissues, and tumors, making it easier to identify and diagnose any pathology. Ultimately, radiation exposure varies by examination prescribed. Find out more with our CT scan cancer risk calculator.
Conclusion
A CT scan provides a painless, non-invasive procedure to quickly acquire diagnostic images. Ultra-low radiation dose technology allows doctors and patients to plan diagnostic procedures without the risk of cancer. Learn more about CT with the additional resources available below.
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