Counsel a parent about radiation risk and consent for a paediatric CT — OSCE

Candidate brief

You have this station to apply the radiation-aware approach to a child referred for a surveillance CT, decide on the imaging in discussion with the anxious parent, and counsel them about the radiation risk and the reasoning behind your decision. Treat this as a communication and decision-making encounter: confirm the clinical context and the justification, communicate the radiation risk in accurate plain language, name the alternatives and the optimisation, and demonstrate the principles of radiation protection and imaging stewardship. [8] [10]

Key teaching and management objectives

Begin by confirming the justification. This child is on a defined oncology surveillance protocol after treatment for a Wilms tumour, and the surveillance CT is justified because the early detection of recurrence changes management; each request is nonetheless a deliberate decision, and the cumulative dose from the previous scans is part of the present discussion. [8]

Counsel the parent about the radiation risk in accurate plain language. A single paediatric CT delivers an effective dose of the order of a few millisievert — a chest or abdominal CT is of the order of 2 to 5 mSv, comparable to around a year or more of natural background radiation (around 2 to 3 mSv per year) — and an attributable lifetime cancer risk of the order of one excess cancer per several thousand to ten thousand scans. Frame it so the parent understands that the risk is real but small, that it rises with cumulative dose which is why the number of scans is kept to the minimum that the surveillance protocol requires, and that the risk of missing a recurrence the scan is looking for is far greater than the risk of the scan. Name the cohort evidence (Brenner and Hall, Pearce) in plain terms. [1] [3]

State the alternatives and the optimisation. Confirm that a non-ionising modality (MRI) is considered for surveillance where it answers the question, and that the oncology protocol already minimises the number of ionising scans. When CT is the modality, the scan is acquired with a size-specific paediatric protocol, a lower kilovoltage peak, automatic tube current modulation, a limited scan length, a single phase, and iterative reconstruction, benchmarked against the size-stratified paediatric diagnostic reference level. [10]

State the three pillars of radiological protection and the ALARA principle — justification (this scan does more good than harm), optimisation (the dose is as low as reasonably achievable), and dose limitation (which applies to staff and the public, not to this justified patient investigation) — and explain that applying them is how the team takes radiation safety seriously. [8]

Document the assessment, the justification, the discussion with the parent, the alternatives considered, and the cumulative dose in the child's imaging history. [8] [10]

Marking domains

• Justification and stewardship (4 marks). Confirms that the surveillance CT is justified by the oncology protocol and a change in management; acknowledges the cumulative dose as part of the present decision; considers a non-ionising substitute where it answers the question; names the three pillars and where dose limitation does and does not apply.
• Radiation-risk counselling (4 marks). States the effective dose and the attributable lifetime cancer risk in plain, accurate language; names the cohort evidence; frames the risk so that the parent consents without minimising or exaggerating it; relates the cumulative-dose principle to the number of scans.
• Optimisation (1 mark). Names the size-specific paediatric protocol, lower kilovoltage peak, single phase and iterative reconstruction; states that the protocol is benchmarked against the size-stratified diagnostic reference level.
• Documentation (1 mark). Documents the justification, the discussion, the alternatives, and the cumulative dose in the imaging history. [8] [10]