Microdosimetry

Baum, J.W. Clonal Theory of Radiation Carcinogenesis, Proceedings of the Symposium on Microdosimetry pp. 12, National Technical Information Service, Springfield, VA, DE 82022044 (1982). 

Fisher, D.R. and R. Harty, The Microdosimetry of Lymphocytes Irradiated by Alpha Particles, 29th Annual Scientific Meeting of the Radiation Research Society. Minneapolis, Minnesota, (April, 1985). 

Since 1925, The International Commission on Radiation Units and Measurements at Bethesda, Maryland has been publishing reports updating the definitions and units for measurements of various radiation-related quantities. Of these ICRU Reports, special mention may be made of reports no. 19 (1971) [radiation quantities and units], 33 (1980) [radiation quantities and units], 36 (1983) [microdosimetry], 47 (1992) [thermoluminiscent dosimetry], and 51 (1993) [radiation protection dosimetry]. A succinct description of various devices used in dosimetry, such as ionization chambers, chemical and solid-state dosimeters, and personnel (pocket) dosimeters, will be found in Spinks and Woods (1990). In this section, we will only consider some chemical dosimeters in a little detail. For a survey of the field the reader is referred to Kase et at, (1985, 1987), McLaughlin (1982), and to the International Atomic Energy Agency (1977). Of the earlier publications, many useful information can still be gleaned from Hine and Brownell (1956), Holm and Berry (1970), and Shapiro (1972). 

In studies conducted at the 1TRI, rats were exposed to 3.5 and 10 mg particles/m air of either F.lftex 12 carbon black or diesel exhaust. These exposures were 7 h/day, 5 days/wk for 12 wk (Wolff et al. Inhal. Toxicol., in press Bond et al. In Assessment of Inhalation Hazards Integration and Extrapolation Using Diverse Data. 1989, in press). Dosimetry (mg particles/g lung), microdosimetry (DNA adducts), pulmonary inflammation, and histopathology of the lungs of... 

Microdosimetry International Commission on Radiological Units and Measurements Washington D.C., 1983 Report No. 36. 

Kobayashi, K. Usami, N. Watanabe, R. Takakura, K. Production yield of adenine form ATP irradiated with monochromatic X-rays in aqueous solution of different concentrations. Goodhead, D.T., O Neill, P., Menzel, H.G., Eds. Microdosimetry—An Interdisciplinary Approach, 1997 65-69 pp. 

The application of microdosimetry to medical physics derives from biological models of radiation action (primarily, the Theory of Dual Radiation Action [14]) that explicitly utilize for their predictions a microdosimetric description of the radiation field. Specifically, they concern the following two problems ... 

The basic concept of microdosimetry is the microdosimetric event (or, simply, event), which is energy deposition by a charged particle and its statistically correlated particles (e.g., secondary electrons from the same particle track) [15-17]. Events are important because they are statistically independent entities. The principal microdosimetric quantity, specific energy z, is defined as follows ... 

In summary, microdosimetry is the study and quantification of the spatial and temporal distributions of absorbed energy in irradiated matter [15,17,22,23]. One makes a distinction between regional microdosimetry [the object of which is the study of micro-dosimetric distributions /(z)j and structural microdosimetry (a mathematically more advanced approach, which is concerned with characterizing the spatial distribution of individual energy deposition events, i.e., ionizations and/or excitations). Regional microdosimetry asserts that the effect is entirely determined by the amount of specific energy deposited in the relevant site (typically, a cell nucleus). The two kinds of microdosimetry, regional and structural, were shown to be in fact mathematically equivalent—once the sensitive site is judiciously determined [16]. 

Microdosimetry provides an unambiguous definition of physical low dose, namely a dose such that n = Djz-pl. Indeed, under these conditions, each cell is essentially traversed by at most one particle. Furthermore ... 

A full description of computational techniques in microdosimetry is beyond the charter of this chapter and the interested reader may consult the textbook by Rossi and Zaider [17]. Briefly, the calculation proceeds along the following lines ... 

International Commission on Radiation Units and Measurements. Microdosimetry 32 ICRU Bethesda, MD, 1983. 

Rossi, H.H. Zaider, M. Microdosimetry and Its Applications Springer-Verlag Berlin, 1996. Cauchy, A. Memoire sur la Rectification des Courbes et la Quadrature des Sourface Courbes. Qevres Completes Gauthier Villard Paris, 1908. 

Energy Distribution at the Microscopic Levei, Microdosimetry, and Bioiogicai Efficiency... 

In hadron therapy, a similar approach and symbolism are presented to take into account the RBE differences. RBE values for neutrons are well documented, and reliable data are now becoming available for protons and heavy ions, on which safe weighting factors IErbe can be based. Besides radiobiological determinations, microdosimetry brings independently additional information on the radiation quality and improves confidence in both sets of data. Microdosimetry provides an objective description of the radiation quality at the point of interest under the actual irradiation conditions. Correlation between this set of information and the experimental RBE results is of great scientific and clinical value in hadron therapy [24,25]. 

Sinclair, W.K. (1983). Fifty years of neutrons in biology and medicine The comparative effects of neutrons in biological systems, page 1 in Proc. Eighth Symposium in Microdosimetry, Booz, J. and Ebert, H., Eds. EUR 8395 (Commission European Communities, Luxembourg). 

Symposium on Microdosimetry, H. G. Ebert and H. D. Hartfiel (eds.). Harwood Academic Publishing for the Commission of the European Communities, Brussels and Luxembourg, 1981, p. 157. 

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