ALARA Principle — MFDS Part 1 MCQ
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Correct answer: A — Keep radiation exposure as low as reasonably achievable while obtaining a diagnostically adequate image.
Option A is correct. ALARA means “as low as reasonably achievable”: radiation exposure should be minimised without compromising the diagnostic purpose of the examination. UK IR(ME)R guidance expresses the equivalent optimisation duty as keeping doses as low as reasonably practicable (ALARP), consistent with the intended purpose. Option E may produce a non-diagnostic image and necessitate another exposure. Option C confuses optimisation with justification; radiographs may be justified before disease is clinically confirmed. Option B is not the definition of ALARA, and shielding cannot replace justification and exposure optimisation. Option D would cause unnecessary repeat exposure because technical perfection is not required when the existing image adequately answers the clinical question.
Reference: Department of Health and Social Care. Guidance to the Ionising Radiation (Medical Exposure) Regulations 2017, Regulation 12: optimisation. Updated 4 September 2024. https://www.gov.uk/government/publications/ionising-radiation-medical-exposure-regulations-2017-guidance/guidance-to-the-ionising-radiation-medical-exposure-regulations-2017