The Use of Effective Dose as a Radiological Protection Quantity

The following review was prepared with contributions from the ESR Radiation Protection Subcommittee members, commenting on behalf of the European Society of Radiology (ESR).

1) Effective dose E was developed as a risk parameter for occupational exposure averaged over gender, age, internal and external exposure and dose rate. Application of E in medicine only makes sense in a few specific situations, e.g. to give rough dose estimates to patients before an exposure comparing different imaging or interventional procedures (e.g. a lung perfusion scintigraphy with a contrast enhanced CT of the lung). Lists of effective doses for common procedures are included in unintended overexposures.
Even in case of age- and gender-corrected risk factors it is important to consider that risk to a general population  is significantly different from risk to patients.  Due to reduced life expectancy - especially incancer patients and other diseases with poor prognosis - the risk to most patients is overestimated.

ESR strongly recommends that E NOT be used for risk calculation of individual patient exposures.

2) Paragraph 121, page 54 states:

''Effective dose (E) in Sievert (Sv) is accepted internationally as the central radiological protection quantity, providing a risk-adjusted measure of total body dose from external and internal sources in relation to stochastic risks of cancer and hereditary effects, expressed in terms of detriment. E has proved to be a valuable and robust quantity for use in the optimisation of protection and setting of dose criteria to control exposures: dose limits, dose constraints and reference levels''.

There is a direct conflict with publication ICRP 135 which states:

“Effective dose is not appropriate as a DRL quantity. Effective dose is not a measurable quantity and does not assess the amount of ionising radiation used to perform a medical imaging task. Its use could introduce extraneous factors that are not needed and not pertinent for the purpose of DRLs.
DRLs are based on national surveys of physical dose parameters like DAP, CTDIvol, DLP, AGD.

ESR recommends that E NOT be used for dose reference levels determination.

3) Paragraphs 24 (page 21) and 125 (page 55) include the same information about the implementation of the radiological protection system. The last 2 sentences of these paragraphs are identical. Editing is needed to avoid repetition of the same information.

4) The role of organ dose is still not clear. The document would benefit from a more-detailed description, specifically in certain examinations (breast dose in CT, or mammography).

5) The most essential part of the text is or should be ''summary and conclusions''. All main points including the comments 1) and 2) must be clearly stated with a sense of completeness in order to pass to the reader the relevant message.