ARRT CT Physics 1 — Questions and Answers
Question 1: What does CT stand for in medical imaging?
- Computed Tomography (Correct answer)
- Cardiac Testing
- Clinical Therapy
- Central Treatment
Correct answer: Computed Tomography
CT (Computed Tomography) uses X-ray technology and computer processing to create detailed cross-sectional images of the body.
Question 2: What is the primary advantage of CT over conventional X-ray?
- CT provides cross-sectional images with superior soft tissue contrast (Correct answer)
- CT uses no radiation
- CT is cheaper
- CT takes less time
Correct answer: CT provides cross-sectional images with superior soft tissue contrast
CT provides detailed cross-sectional images with much better soft tissue contrast resolution than conventional X-rays, allowing visualization of subtle differences between tissues.
Question 3: What is the purpose of contrast media in CT scans?
- To enhance the visibility of specific structures and pathology (Correct answer)
- To reduce radiation dose
- To speed up the scan
- To make the patient comfortable
Correct answer: To enhance the visibility of specific structures and pathology
Contrast media (dye) enhances the visibility of blood vessels, organs, and abnormalities by changing how X-rays interact with specific tissues.
Question 4: What is the ALARA principle in radiation safety?
- As Low As Reasonably Achievable — minimize radiation exposure (Correct answer)
- Always Lock And Restrict Access
- Automated Limiting Adjustment for Radiation Applications
- All Labs And Rooms Assessed
Correct answer: As Low As Reasonably Achievable — minimize radiation exposure
ALARA means keeping radiation doses as low as reasonably achievable while still obtaining diagnostic-quality images, balancing benefit against risk.
Question 5: What is a Hounsfield unit?
- A quantitative measurement of tissue density on CT images (Correct answer)
- A unit of radiation dose
- A measure of scan speed
- A unit of image resolution
Correct answer: A quantitative measurement of tissue density on CT images
Hounsfield units (HU) measure tissue density on CT, with water at 0 HU, air at -1000 HU, and dense bone at +1000 HU or higher.
Question 6: What is the window level and window width on CT images?
- Settings that control the brightness and contrast of displayed images (Correct answer)
- Physical measurements of the CT scanner
- Patient positioning parameters
- Scan speed controls
Correct answer: Settings that control the brightness and contrast of displayed images
Window level sets the center brightness (what HU appears as middle gray) and window width controls contrast range (how many HUs span from black to white).
ARRT CT Physics 1
What does CT stand for in medical imaging?