ARRT Radiation Protection Principles 4 β Questions and Answers
Question 1: Which cell type is considered the most radiosensitive in the human body?
- Neurons
- Muscle cells
- Lymphocytes (Correct answer)
- Osteocytes
Correct answer: Lymphocytes
Lymphocytes are highly radiosensitive and show decreases in count at relatively low doses, making them a useful biological indicator of exposure.
Question 2: The occupational lens of eye dose limit per year is set at what value by NCRP?
- 15 mSv
- 50 mSv
- 75 mSv
- 150 mSv (Correct answer)
Correct answer: 150 mSv
NCRP sets the annual occupational equivalent dose limit for the lens of the eye at 150 mSv (15 rem).
Question 3: Which factor describes the relative biological effectiveness of different radiation types and is used to calculate equivalent dose?
- Tissue weighting factor (wT)
- Quality factor (Q) or radiation weighting factor (wR) (Correct answer)
- Attenuation coefficient (ΞΌ)
- Linear energy transfer (LET) only
Correct answer: Quality factor (Q) or radiation weighting factor (wR)
The radiation weighting factor (wR), formerly called quality factor, converts absorbed dose to equivalent dose by accounting for radiation type's biological effectiveness.
Question 4: Adding filtration to an X-ray beam primarily reduces patient dose by:
- Decreasing the number of high-energy photons
- Removing low-energy photons that would be absorbed in superficial tissues (Correct answer)
- Increasing beam intensity overall
- Reducing the kVp of the beam
Correct answer: Removing low-energy photons that would be absorbed in superficial tissues
Added filtration (typically aluminum) absorbs low-energy photons that would deposit dose in superficial tissue without contributing to the image.
Question 5: What is the minimum total filtration required for X-ray tubes operating above 70 kVp, per federal regulation?
- 0.5 mm Al equivalent
- 1.0 mm Al equivalent
- 2.5 mm Al equivalent (Correct answer)
- 3.5 mm Al equivalent
Correct answer: 2.5 mm Al equivalent
Federal regulations (21 CFR 1020.30) require a minimum total filtration of 2.5 mm aluminum equivalent for tubes operating above 70 kVp.
Question 6: Which radiation protection action most directly reduces scatter to the patient during a radiographic exam?
- Increasing SID
- Using a grid
- Collimating the field to the area of interest (Correct answer)
- Using higher kVp
Correct answer: Collimating the field to the area of interest
Collimation reduces the volume of irradiated tissue, which directly decreases the amount of scatter produced within the patient.
Question 7: Which organization establishes radiation protection recommendations that form the basis of US regulatory dose limits?
- ARRT
- ASRT
- NCRP (National Council on Radiation Protection and Measurements) (Correct answer)
- ACR (American College of Radiology)
Correct answer: NCRP (National Council on Radiation Protection and Measurements)
The NCRP issues scientific recommendations on radiation protection that are adopted by federal and state regulatory agencies in the US.
ARRT Radiation Protection Principles 4
Which cell type is considered the most radiosensitive in the human body?