Synopsis
Explain stochastic and tissue effects, distinguish justification from optimisation, and use diagnostic reference levels correctly without treating them as individual dose limits.
- Justification decides whether an individual medical exposure has sufficient net benefit before it is authorised.
- Optimisation individualises the authorised examination to obtain diagnostic information at the lowest practicable dose.
- Diagnostic reference levels are population-based review tools for typical examinations, not individual patient dose limits.
Key red flags
Repeating an exposure because prior images or reports were not checked is an avoidable safety failure.
Children, pregnancy, interventional procedures and repeated high-dose studies require explicit attention during optimisation.
A protocol substantially above its diagnostic reference level should trigger local investigation rather than automatic blame of one case.
Wrong patient, wrong anatomy, major protocol error, equipment failure or other significant deviation requires immediate local safety action.
Reasoning priorities
Identify prior relevant examinations and cumulative procedural context.
Previous exposure is not an absolute contraindication but may reveal an existing answer or support a different technique.
Worked reasoning
A recent CT may already answer the proposed repeat examination.
- Context: identify the new clinical question, interval change and management decision expected from another exposure.
- Reasoning: retrieve the previous images and report, and consider whether review, comparison or a non-ionising test suffices.
- Outcome: the practitioner justifies only if added information creates net benefit, then the operator tailors the protocol.
- Verification: record the authorisation, confirm diagnostic image quality and review local dose metrics after acquisition.
An ionising examination is proposed for a defined clinical problem.