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Submitted by Russell Robinson, N/A
   Commenting as an individual
Document Dosimetric quantities
 
There is some incoherence in the definition of effective dose. After applying various weighting factors for different types of radiation, organ and tissue differences, the unit of effective dose remains as joule per kilogram even though various factors have scaled the value. This document should provide some clarification on this apparent incoherence in SI unit coherence.

Another way of clarifying this point is to return to the concept of effective dose as risk and dimensionless (see Supplement to international Commission on Radiation Units and Measurements (ICRU) Report Number 19 page 1). ICRU suggested that effective dose, given the name dose equivalent at the time, could be considered as a dimensionless quantity and represent risk properly. The reason for not adopting this meaning was the lack of knowledge of different radio sensitivities of tissues and organs at the time.

Inevitably, knowledge of relative radio sensitivities will increase and it follows that effective dose could eventually be considered dimensionless and represent risk properly as a dimensionless quantity, overcoming the apparent incoherence in the SI system of units.

Sievert could still be applied to effective dose. Erroneous decisions following the use of sievert for both equivalent dose and effective dose may occur but a dimensionless sievert unit (similar to the neper) could be used for effective dose only and radiation weighted dose could have a differently named unit.