GENERAL REQUIREMENTS

 

Recent intercomparison exercises have shown that there is a wide variety of evaluation procedures, depending on the experience and the skill of the assessor as well as on the hardware and software tools available. However, for a given set of internal monitoring data in terms of body/organ activity and/or urine/faecal activity there can be only one best estimate for the intake and the committed dose equivalent. This best estimate is defined by the monitoring data, the biokinetic models for the description of the metabolism, and – if available - some additional information, such as time of intake, route of intake, aerosol size, absorption type, f1-factor and previous internal exposures. The aim of the IDEAS project is to provide general guidelines which enable all assessors to derive this standard estimate for any given set of data. This of great importance for the harmonisation of internal dose assessment in Europe, and elsewhere.

 

The results of internal dosimetry in terms of committed dose should be comparable to the results of external dosimetry with respect to accuracy and reproducibility. If two persons are exposed to the same external irradiation field then their dosemeter readings are consistent with each other, and they are considered to give the best estimate of the exposure. In some special cases the dose reading might be wrong because of some uncommon photon energy or some uncommon radiation incidence angle, but nobody worries about it so long as the dose reading is below the investigation level. In internal dosimetry we should come to a similar philosophy, that means if two persons have the same internal exposure then the results of internal monitoring in terms of committed dose should be consistent with each other, and the results should be considered to be the best estimate. Similarly, in some special cases the results might be wrong because of some uncommon pattern of intake or some uncommon physical/chemical properties of the incorporated material, but nobody should worry about it as long as the committed dose is below the investigation level.

 

So, in internal dosimetry the reproducibility of the results should have the same priority as in external dosimetry. This means, first of all, that the monitoring procedure should be optimised in such a way that the monitoring results, in terms of activity, are representative for the real exposure. This optimisation recently has been provided by the OMINEX project (Optimisation of Monitoring for Internal Exposure). The second step is the optimisation of the evaluation of the monitoring data, which is provided by the IDEAS project. So both projects focus on the same goal, but with clearly distinct approaches: OMINEX optimising the procedures for carrying out monitoring, and IDEAS optimising the procedures for assessing doses from the results of monitoring.