Module 8 - Minimizing Patient Dose, Dose Limits and DRLs Flashcards
(25 cards)
What is the primary goal of radiation protection in medical imaging?
To minimize unnecessary exposure while achieving diagnostic image quality.
What is ALARA?
“As Low As Reasonably Achievable” – a principle to minimize radiation exposure.
Name three methods to reduce patient dose in fluoroscopy.
1) Use intermittent fluoroscopy, 2) Minimize beam-on time, 3) Use last image hold.
How does increasing distance from the radiation source affect dose?
It decreases the dose, following the inverse square law.
What are DRLs, and why are they important?
Diagnostic Reference Levels – used to compare typical doses and identify outliers.
What is the annual effective dose limit for radiation workers in Canada?
20 mSv per year, averaged over 5 years, with a maximum of 50 mSv in any one year.
What is the dose limit for the public in Canada?
1 mSv per year.
What is the main purpose of personal dosimeters?
To monitor radiation exposure of workers.
What are the two common types of dosimeters?
Thermoluminescent dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs).
What is a controlled area?
An area where radiation exposure is monitored and controlled to protect workers.
How does increasing kVp affect patient dose?
It reduces patient dose but may decrease image contrast.
What is the purpose of filtration in X-ray systems?
To remove low-energy photons, reducing skin dose and enhancing image quality.
What does collimation do?
It reduces the exposed area, limiting unnecessary radiation.
What is the benefit of using a grid during imaging?
It reduces scatter radiation, improving image contrast.
How does automatic exposure control (AEC) help in dose management?
It adjusts exposure automatically, preventing overexposure.
What is the purpose of lead aprons?
To protect against scatter radiation.
What thickness of lead is standard for aprons in diagnostic imaging?
0.25–0.5 mm lead equivalent.
Why are thyroid collars used?
To shield the thyroid gland from radiation exposure.
What is time-distance-shielding?
A protection principle: reduce time near the source, increase distance, and use shielding.
What are protective barriers?
Fixed or mobile shields (e.g., lead-lined walls) to reduce radiation exposure.
What organization regulates radiation protection in Canada?
Canadian Nuclear Safety Commission (CNSC).
What is a controlled dose level?
A dose level that must be monitored and kept within regulatory limits.
What is the main purpose of quality assurance (QA) programs?
To ensure consistent image quality and radiation safety.
What is the maximum allowable leakage radiation from an X-ray tube?
1 mGy/hr at 1 meter from the tube.
