THE COMPLEXITY OF QUANTITIES IN RADIATION DOSIMETRY: THE ISSUE OF RADIATION QUALITY.

Abstract

When Harald Rossi developed a new radiation measurement instrument more than 60 years ago-the tissue equivalent low-pressure proportional counter, also called Rossi Counter-his initial intention was to provide a technique to measure LET. He realized soon that the measurements provided insight into the stochastic nature of the interactions of ionizing radiation with matter and that the measured results represented an alternative to characterize radiation quality in terms of stochastic or microdosimetric quantities. Progress in cellular and molecular radiation biology and in simulating charged particle tracks in biological entities are now essential features and have extended the original delineation of the field of microdosimetry. This general field of microdosimetry, as part of an interdisciplinary approach for the study of molecular mechanisms and cellular radiation effects, continues to be an important area of radiation research, documented by 13 previous Microdosimetry Symposia and, again, at this Symposium. However, the quantification of radiation quality remains a subject of practical importance. In fact, the issue has gained in importance due to the application of ions for therapy and due to the need for protection from exposures to complex and high-energy radiation fields, for example, to cosmic radiation in civil aviation and space missions. In practice pragmatic, empirical approaches are being used which has led to a complex set of dosimetric quantities and terms.