RAS question
Which radiation is used in a CT (Computed Tomography) scan?
Correct answer: (C) X-rays.
A CT scan uses X-rays to create computer-processed cross-sectional images of the body.
Explanation
Computed tomography is a computerized X-ray imaging procedure, so the radiation used in a CT scan is X-rays. In a CT scanner, a narrow beam of X-rays is aimed at the patient and the X-ray source rotates around the body. Detectors pick up the X-rays after they pass through the patient and send the signals to a computer. The computer then constructs cross-sectional images, or slices, which can be viewed one by one or stacked to form a 3D image. This is why CT is useful for showing structures such as bones, blood vessels and soft tissues in more detail than a single conventional X-ray image.
Why the other options are wrong
- (A) Infrared rays are associated with thermal imaging, while CT works by sending X-rays through the body and processing the detected signals into slices.
- (B) Ultraviolet rays are not the radiation used for CT, which the official source describes as a computerized X-ray imaging procedure.
- (D) Gamma rays are used in PET scans and gamma cameras, whereas CT uses X-rays from a rotating source to build cross-sectional images.
Concept
This tests the Science and Technology concept of electromagnetic radiation in medical imaging. It recurs in RAS because exam questions often ask devices through their operating principle, not just their name.