Optimisation of Dose

Radiation ProtectionFor every x-ray exposure, the dose arising from the exposure must be kept as low as reasonably practicable consistent with the intended diagnostic purpose. This is known as optimisation and relies as much on the professional competence and skill of the Operator as on operating procedures and protocols.

Diagnostic reference levels (DRLs) are defined in IR(ME)R [1] as dose levels in radiodiagnostic practices for typical examinations for groups of standard-sized patients for broadly defined types of equipment, and it is expected that these DRLs would not normally be exceeded without good reason. Note that DRLs relate to mean doses for groups of patients and so apply to typical practice rather than individual exposures.

Example Employer’s Procedures for the procedures denoted * and example Protocols for Exposures can be downloaded via Written Procedures and Protocols.

In order to ensure that patient doses arising from the exposure are as low as reasonably practicable:

Put in place written protocols for every type of standard projection for each x-ray machine, including exposure settings, and include them in the Radiation Protection Filesee example Protocols for Exposures). These protocols should also be readily available adjacent to the x-ray equipment.

Consult with your Medical Physics Expert and put in place local DRLs* (see EP7 Diagnostic Reference Levels example Employer’s Procedure). These should take into account national reference dose values [2], where available.

If a non-standard exposure is employed, the exposure factors relevant to the patient dose should be recorded so that the patient dose can be estimated at a later date if required* (see EP6 Assessment of Patient Dose example Employer’s Procedure).

Ensure that all radiographs are clinically evaluated and the outcome of each exposure recorded with enough information provided to allow for audit at a later date* (see EP8 Clinical Evaluation example Employer’s Procedure). If it is known prior to the exposure that the radiograph will not be clinically evaluated then the exposure is not justified and must not take place.

During acceptance testing and at each routine test, compare the representative patient dose with the local DRL. If patient doses are consistently above the DRL, undertake a review of radiographic practice to improve current techniques or to justify their continued use.

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