Which is NOT considered one of the cardinal principles of radiation protection for personnel?

Which is NOT considered one of the cardinal principles of radiation protection for personnel?

• A. Distance
• B. Collimation
• C. Shielding
• D. Time

Answer: (B)

The main idea here is understanding the three fundamental ways to protect personnel: increasing distance from the source, reducing the exposure time, and using shielding to block or absorb radiation. Collimation isn’t one of these core levers. It’s a beam-restriction technique that narrows the X-ray field to the area of interest, which helps lower dose by reducing scattered radiation and unnecessary exposure, but it’s not counted as one of the three cardinal principles itself. So, while collimation is essential for dose management and image quality, the established trio of protections remains distance, time, and shielding.

The main idea here is understanding the three fundamental ways to protect personnel: increasing distance from the source, reducing the exposure time, and using shielding to block or absorb radiation. Collimation isn’t one of these core levers. It’s a beam-restriction technique that narrows the X-ray field to the area of interest, which helps lower dose by reducing scattered radiation and unnecessary exposure, but it’s not counted as one of the three cardinal principles itself. So, while collimation is essential for dose management and image quality, the established trio of protections remains distance, time, and shielding.