MJDF Radiology & IRMER 1 — Questions and Answers
Question 1: What does IRMER 2017 stand for and what does it primarily regulate?
- Ionising Radiation (Medical Exposure) Regulations 2017 — regulates medical exposures to ionising radiation, including dental radiography (Correct answer)
- Infection Risk Management Emergency Regulations
- Internal Radiation Monitoring Equipment Regulations
- International Radiological Medical Ethics Requirements
Correct answer: Ionising Radiation (Medical Exposure) Regulations 2017 — regulates medical exposures to ionising radiation, including dental radiography
IRMER 2017 is the UK statutory instrument regulating medical (including dental) exposures to ionising radiation, requiring justification, optimisation (ALARP), and dose limitation for all radiographic examinations.
Question 2: What is the 'ALARP' principle in radiation protection?
- As Low As Reasonably Practicable — minimising radiation dose while maintaining diagnostic quality (Correct answer)
- As Large As Reasonably Practicable
- A Level Above Routine Practice
- Acceptable Limit And Radiation Protection
Correct answer: As Low As Reasonably Practicable — minimising radiation dose while maintaining diagnostic quality
ALARP requires that radiation doses be kept as low as is reasonably practicable, balancing the reduction of radiation risk against the practical (cost, effort) measures required to achieve it.
Question 3: Which radiograph delivers the highest radiation dose to the patient in routine dental practice?
- Cone beam CT (CBCT) (Correct answer)
- Periapical radiograph
- Bitewing radiograph
- Panoramic (OPG)
Correct answer: Cone beam CT (CBCT)
CBCT delivers the highest patient dose in routine dental imaging, ranging from 30 µSv (limited FOV) to over 1,000 µSv (large FOV, high-resolution protocols), depending on the FOV and machine settings.
Question 4: What is the effective radiation dose of a standard full-mouth periapical series compared to a panoramic radiograph?
- Full mouth series: ~150–170 µSv; panoramic: ~6–22 µSv (modern systems) (Correct answer)
- Panoramic is always higher
- Both deliver identical doses
- Full mouth series is lower than panoramic
Correct answer: Full mouth series: ~150–170 µSv; panoramic: ~6–22 µSv (modern systems)
A full-mouth periapical series (18 films) typically delivers a higher cumulative dose than a panoramic radiograph; modern digital panoramic systems significantly reduce dose compared to film panoramics.
Question 5: Under IRMER 2017, what responsibility does the 'Operator' have?
- Practically carries out the exposure — positions the patient and equipment, presses the exposure button, processes the image (Correct answer)
- Authorises the examination (justification)
- Refers the patient for the examination
- Manages the radiation protection policies
Correct answer: Practically carries out the exposure — positions the patient and equipment, presses the exposure button, processes the image
The Operator is the person who physically carries out the radiographic exposure under an employer's written procedures; operators must ensure correct positioning, exposure settings, and processing as per protocols.
Question 6: What is the difference between deterministic and stochastic radiation effects?
- Deterministic effects have a threshold dose (e.g., cataract, erythema); stochastic effects are probabilistic with no threshold (e.g., cancer induction) (Correct answer)
- They are identical in mechanism
- Stochastic effects have a clear threshold
- Deterministic effects include cancer only
Correct answer: Deterministic effects have a threshold dose (e.g., cataract, erythema); stochastic effects are probabilistic with no threshold (e.g., cancer induction)
Deterministic effects (e.g., cataract, skin reactions) occur above a threshold dose and increase in severity with dose; stochastic effects (e.g., cancer) have no threshold — any dose has a small probability of harm.
MJDF Radiology & IRMER 1
What does IRMER 2017 stand for and what does it primarily regulate?