L. Braby - Academia.edu (original) (raw)
Papers by L. Braby
Radiation Protection Dosimetry, 1995
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of Food Process Engineering, 2010
In the design of the food irradiation process, the knowledge of the radiation resistance of the t... more In the design of the food irradiation process, the knowledge of the radiation resistance of the target organism in the specific food commodity is required. The D 10-value, the radiation dose needed to inactivate 90% of the microbial load in the food medium, is used to relate the amount of absorbed energy to the fractional population of the viable cells. Numerous experimental studies have been performed to determine the D 10 values of several food borne microorganisms irradiated under various conditions. Nevertheless, accurate prediction of D 10 value for a radiation treatment of a food product that has not been empirically examined can not be made due to insufficient understanding of the biological response to radiation exposure. A theoretical model for the derivation of the D 10-value has been proposed in this study to mechanistically assess the DNA damage by energetic electrons. The step-by-step Monte-Carlo simulation technique which employed the detailed histories of the ionizing particles and the radiolytic species was utilized. The impacts of the genomic sequence, the number of the genome equivalents, and the method of DNA double strand break determination were hypothetically investigated. The developed computational methodology as well as the results presented can be used as an analytical tool to evaluate the effect of ionizing radiation on the cell survival. PRACTICAL APPLICATIONS The presented methodology can be employed as an investigative technique complementary to other approaches to understand the physical, chemical and biological changes in food-born pathogens exposed to e-beam.
Journal of Food Process Engineering, 2010
In the design of the food irradiation process, the knowledge of the radiation resistance of the t... more In the design of the food irradiation process, the knowledge of the radiation resistance of the target organism in the specific food commodity is required. The D 10-value, the radiation dose needed to inactivate 90% of the microbial load in the food medium, is used to relate the amount of absorbed energy to the fractional population of the viable cells. Numerous experimental studies have been performed to determine the D 10 values of several food borne microorganisms irradiated under various conditions. Nevertheless, accurate prediction of D 10 value for a radiation treatment of a food product that has not been empirically examined can not be made due to insufficient understanding of the biological response to radiation exposure. A theoretical model for the derivation of the D 10-value has been proposed in this study to mechanistically assess the DNA damage by energetic electrons. The step-by-step Monte-Carlo simulation technique which employed the detailed histories of the ionizing particles and the radiolytic species was utilized. The impacts of the genomic sequence, the number of the genome equivalents, and the method of DNA double strand break determination were hypothetically investigated. The developed computational methodology as well as the results presented can be used as an analytical tool to evaluate the effect of ionizing radiation on the cell survival. PRACTICAL APPLICATIONS The presented methodology can be employed as an investigative technique complementary to other approaches to understand the physical, chemical and biological changes in food-born pathogens exposed to e-beam.
Reports of the International Commission on Radiation Units and Measurements, 1983
Reports of the International Commission on Radiation Units and Measurements, 1983
Reports of the International Commission on Radiation Units and Measurements, 1983
a surface area of the volume of interest H dose equivalent ax total Auger-electron yield 'Y r... more a surface area of the volume of interest H dose equivalent ax total Auger-electron yield 'Y relative effective charge ax; Auger-electron yield of subshell i of the I mean excitation energy major shell X (i = 1,2, etc.; X = L, M, etc.) J number of ion pairs A atomic weight J mean number of ion pairs Ar relative atomic mass ke electron momentum divided by moe a photon energy divided by the electron K atomic shell designation rest-mass energy I chord length in the volume of interest O:T Townsend's first ionization coefficient I mean chord length in the volume of Ii velocity of a particle divided by the interest velocity of light in vacuum L atomic shell designation c velocity of light in vacuum Lt:. linear energy transfer, restricted linear Cj shell corrections (i = 1,2, etc.) collision stopping power d diameter L .. unrestricted linear energy transfer d(y) probability density of absorbed dose in y m mass in the volume of interest d(z) probability density of absorbed dose in z mo rest mass of electron d1(z) probability density of absorbed dose in z me mass of moving electron for single energy deposition events mp particle mass D absorbed dose M atomic shell designation D(y) absorbed dose distribution with events :S;y MA molar mass of substance A D(z) absorbed dose distribution with specific N number of atoms per unit volume energy:S;z NA Avogadro constant D1(z) absorbed dose distribution per event for neE) initial (energy) spectrum of charged events of specific energy :S;z particles directly after their generation e elementary charge n number of energy deposition events of E particle energy specific energy EB binding energy v frequency of light Ei excitation energy p pressure AE mean particle energy loss P mean energy expended per minimum E electric field strength observable energy deposition event
Journal of the International Commission on Radiation Units and Measurements, 1983
In this appendix the elemental composition of the most frequently used tissue-equivalent compound... more In this appendix the elemental composition of the most frequently used tissue-equivalent compounds and mixtures are listed as well as some of their material constants which are relevant for microdosimetry: mass energy transfer coefficients for photons of 100 keY to 10 MeV (Table C.3), kerma factors for fast neutrons of 11 keY to 20 MeV (Table C.4), stopping powers for electrons of 100 eV to 80 MeV (Table C.5), and for protons and alpha particles of 10 ke V to 100 Me V (Tables C.6 and C.7)11. All of the tables give the absolute material constants for ICRU tissue (ICRU, 1964), and, for all other compounds and mixtures, the relative material constants, relative to ICRU tissue. This was done in order to allow for a quick orientation as to the interactions and energy ranges for which a particular compound or mixture can be regarded as tissue equivalent.
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
There are a number of relationships between microdosimetric quantities and their macroscopic anal... more There are a number of relationships between microdosimetric quantities and their macroscopic analogues. Some of these are of a general nature and follow from the definition of the quantity or can be derived mathematically. Others are restricted to a particular geometry or utilize a specific approximation, such as the continuous slowing down approximation (csda). When such restrictions are present, it will be explicitly noted; otherwise, the relationships can be assumed to be generally valid. All formulae given here, and others, are tabulated in a summary of microdosimetric quantities by Kellerer and Rossi (1970). Definition of the relevant variables, energy imparted. f, specific energy, z, and lineal energy, y , as well as the definition of their distributions have been given in Section 2 and will not be repeated here.
Journal of the International Commission on Radiation Units and Measurements, 1983
Experiments and calculations of microd08imetric spectra play complementary roles. The degree of a... more Experiments and calculations of microd08imetric spectra play complementary roles. The degree of agreement between experiment and theory serves as a test of the validity of both. Each can extend the other-theory by calculation of spectra for wide ranges of parameters impossible or difficult to measure, experiment by measurement of spectra where input data for calculation is not available. With currently available methods, microdosimetric distributions of ionization can be measured only for simulated volumes of unit density material having linear dimensions larger than about 0.3 ~m. In addition, the standard deviation of the distribution of ion yield can be determined experimentally for volume sizes down to 10 nm. These experimental techniques can be applied without major correction to gamma-rays of 50 keV to 5 MeV, thermal neutrons, and fast neutrons below 10 Me V. However, outside of this energy range, and for other types of radiations, corrections may be necessary, in particular, for insufficient tissue equivalence. If the primary cross sections are known for these energies, calculations are probably more accurate than measurements. Once adequate mathematical formulations and algorithms have been developed, it is less time consuming to calculate lineal energy spectra for a large variety of physical conditions, for example, different energies for the incident radiation, different cavity sizes and different composition for the wall and the gas, than to measure them. However, it must always be kept in mind that calculations may involve simplifying assumptions, which may not yield adequately accurate results. In addition to the description of the methods for calculating lineal energy spectra, this chapter will also deal with the methods of calculating f(z) as a function of absorbed dose. Finally, the convolution of f(z) for inhomogeneously distributed radiation sources will be considered. Monte-Carlo computer programs which permit detailed simulation of structured charged-particle tracks are dealt with in Section 4.3.
Journal of the International Commission on Radiation Units and Measurements, 1983
In analytical calculations, the cada is applied and it is assumed that the charged particles prod... more In analytical calculations, the cada is applied and it is assumed that the charged particles produced travel in straight lines. Formulae for the single-event distributions of energy imparted that result with this assumption will be given for one type of particle; the generalization to a mixed field of different particles is evident. Important auxiliary functions are the chord length distributions that result from the random transversal of convex volumes. Kellerer (1971b) discusses two different kinds of randomness relevant in the present context: Mean free path randomness (p.-randomness). A chord of a convex body is dermed by a point in Euclidian space and a direction. The point and the direction are from independent uniform distributions. This randomness results if the convex body is exposed to a uniform isotropic field of straight infinite tracks. Internal source randomness (i-randomness). A segment is dermed by a point in the interior of a convex body and a direction. The point and the direction are from independent uniform distributions. This i-randomness is what one obtains if the interior of the body is a uniform source of straight particle tracks. The probability densities for p.-randomness, I,. (I), and for i-randomness, Ii (l), are related by fi(l) = t So '" I I,.(x) dx, (E.l)
Journal of the International Commission on Radiation Units and Measurements, 1983
Advances in Space Research, 1994
We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we... more We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a 'second' radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements, 1992
Journal of the International Commission on Radiation Units and Measurements
Most counters in use today are variations and modifications of the original Rossi counter (Rossi ... more Most counters in use today are variations and modifications of the original Rossi counter (Rossi and Rosenzweig, 1955a, 1955b) developed at the Radiological Research Laboratories of Columbia University. For a review of the theory and practice of proportional counter operation see, for example, Emery (1966) or Franzen and Cochran (1962). Section 5 of this report contains a discussion of the practical application of proportional counters to microdosimetry. This Appendix will be concerned with some of the important technical details relating to construction.
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
This appendix is a compilation of representative published values of dose-mean lineal energy, YD,... more This appendix is a compilation of representative published values of dose-mean lineal energy, YD, and of frequency-mean lineal energy, YF. It does not pretend to be exhaustive. The large number of variables involved in the experimental determinations of y spectra, e.g., volume size, type of counter, experimental conditions, quality of the beam, etc., influences the mean values. Calculations require parameters, such as cross sections, stopping power etc., which may cause discrepancies between the results of different authors. As indicated in Section 5, the systematic uncertainty in the experimental determination of YF may reach ±30%, mainly related to the extrapolation method used. For this reason, experimental YF values are not given here. The maximal systematic uncertainty one can expect on YD determinations may be estimated at ±10% if the irradiation conditions are identical. But, as irradiation conditions may vary, the values given in the tabulation should be taken only as an indication of the possible range of YD for a given site size and a given particle energy. Figure F.1 gives the variation ofYD as a function of photon energy for different site sizes. Figures F.2 and F.3 show the variation ofYD for 60CO gamma rays with simulated size down to about 0.3 J,Lm. Data points for smaller object sizes can be found in the literature, for instance, for x rays in Forsberg et al. (1978) and for 6OCO 'Y rays in Forsberg and Lindborg (1981). Figure F.4 illustrates the ratios (€lEo) and (tl/Eo2)(EoIt'J calculated by Berger (1974) for monoenergetic electrons of energy
Journal of the International Commission on Radiation Units and Measurements, 1983
The historical background, concepts, fundamentals, and techniques of microdosimetry have been rev... more The historical background, concepts, fundamentals, and techniques of microdosimetry have been reviewed in the first six chapters of this report. This section is concerned with a description of some of the conceptUal and practical methodology useful in the interpretation of a microdosimetric spectrum. It is the intent to set forth in this section the fundamental principles underlying the composition of microdosimetric spectra, in such a way that these principles can be applied to a variety of circumstances. The large number of variables involved. in the ~ormation of any given spectrum, e.g., volume SIZe, particle type, and various statistical factors discussed in Section 5, in general, precludes trivial ic;ientifications. But if some of these factors are known , an understanding of fundamentals may allow an estimate of others. Such interpretation is essential for many applications of microdosimetry (see Section 8). Figure 7.1 is an example which illustrates some of the general features of microdosimetric spectra for photons and neutrons of differing energies. Of special interest is the wide range of lineal energies involved and the changes of shape with energy. The greater part of this section deals with the composition and interpretation of single-event spectra which result from experiments with proportional counters or from calculation. The principles underlying the production of such a spectrum in terms of contributions from a single type of particle of fixed energy are outlined, and then the contributions of different particles and different energies are considered. Examples of interpretation of some important radiation modalities are then shown and discussed. Finally, the last part of this section deals with formation and interpretation of multiple-event, i.e., dose-dependent spectra.
Radiation Protection Dosimetry, 1995
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of Food Process Engineering, 2010
In the design of the food irradiation process, the knowledge of the radiation resistance of the t... more In the design of the food irradiation process, the knowledge of the radiation resistance of the target organism in the specific food commodity is required. The D 10-value, the radiation dose needed to inactivate 90% of the microbial load in the food medium, is used to relate the amount of absorbed energy to the fractional population of the viable cells. Numerous experimental studies have been performed to determine the D 10 values of several food borne microorganisms irradiated under various conditions. Nevertheless, accurate prediction of D 10 value for a radiation treatment of a food product that has not been empirically examined can not be made due to insufficient understanding of the biological response to radiation exposure. A theoretical model for the derivation of the D 10-value has been proposed in this study to mechanistically assess the DNA damage by energetic electrons. The step-by-step Monte-Carlo simulation technique which employed the detailed histories of the ionizing particles and the radiolytic species was utilized. The impacts of the genomic sequence, the number of the genome equivalents, and the method of DNA double strand break determination were hypothetically investigated. The developed computational methodology as well as the results presented can be used as an analytical tool to evaluate the effect of ionizing radiation on the cell survival. PRACTICAL APPLICATIONS The presented methodology can be employed as an investigative technique complementary to other approaches to understand the physical, chemical and biological changes in food-born pathogens exposed to e-beam.
Journal of Food Process Engineering, 2010
In the design of the food irradiation process, the knowledge of the radiation resistance of the t... more In the design of the food irradiation process, the knowledge of the radiation resistance of the target organism in the specific food commodity is required. The D 10-value, the radiation dose needed to inactivate 90% of the microbial load in the food medium, is used to relate the amount of absorbed energy to the fractional population of the viable cells. Numerous experimental studies have been performed to determine the D 10 values of several food borne microorganisms irradiated under various conditions. Nevertheless, accurate prediction of D 10 value for a radiation treatment of a food product that has not been empirically examined can not be made due to insufficient understanding of the biological response to radiation exposure. A theoretical model for the derivation of the D 10-value has been proposed in this study to mechanistically assess the DNA damage by energetic electrons. The step-by-step Monte-Carlo simulation technique which employed the detailed histories of the ionizing particles and the radiolytic species was utilized. The impacts of the genomic sequence, the number of the genome equivalents, and the method of DNA double strand break determination were hypothetically investigated. The developed computational methodology as well as the results presented can be used as an analytical tool to evaluate the effect of ionizing radiation on the cell survival. PRACTICAL APPLICATIONS The presented methodology can be employed as an investigative technique complementary to other approaches to understand the physical, chemical and biological changes in food-born pathogens exposed to e-beam.
Reports of the International Commission on Radiation Units and Measurements, 1983
Reports of the International Commission on Radiation Units and Measurements, 1983
Reports of the International Commission on Radiation Units and Measurements, 1983
a surface area of the volume of interest H dose equivalent ax total Auger-electron yield 'Y r... more a surface area of the volume of interest H dose equivalent ax total Auger-electron yield 'Y relative effective charge ax; Auger-electron yield of subshell i of the I mean excitation energy major shell X (i = 1,2, etc.; X = L, M, etc.) J number of ion pairs A atomic weight J mean number of ion pairs Ar relative atomic mass ke electron momentum divided by moe a photon energy divided by the electron K atomic shell designation rest-mass energy I chord length in the volume of interest O:T Townsend's first ionization coefficient I mean chord length in the volume of Ii velocity of a particle divided by the interest velocity of light in vacuum L atomic shell designation c velocity of light in vacuum Lt:. linear energy transfer, restricted linear Cj shell corrections (i = 1,2, etc.) collision stopping power d diameter L .. unrestricted linear energy transfer d(y) probability density of absorbed dose in y m mass in the volume of interest d(z) probability density of absorbed dose in z mo rest mass of electron d1(z) probability density of absorbed dose in z me mass of moving electron for single energy deposition events mp particle mass D absorbed dose M atomic shell designation D(y) absorbed dose distribution with events :S;y MA molar mass of substance A D(z) absorbed dose distribution with specific N number of atoms per unit volume energy:S;z NA Avogadro constant D1(z) absorbed dose distribution per event for neE) initial (energy) spectrum of charged events of specific energy :S;z particles directly after their generation e elementary charge n number of energy deposition events of E particle energy specific energy EB binding energy v frequency of light Ei excitation energy p pressure AE mean particle energy loss P mean energy expended per minimum E electric field strength observable energy deposition event
Journal of the International Commission on Radiation Units and Measurements, 1983
In this appendix the elemental composition of the most frequently used tissue-equivalent compound... more In this appendix the elemental composition of the most frequently used tissue-equivalent compounds and mixtures are listed as well as some of their material constants which are relevant for microdosimetry: mass energy transfer coefficients for photons of 100 keY to 10 MeV (Table C.3), kerma factors for fast neutrons of 11 keY to 20 MeV (Table C.4), stopping powers for electrons of 100 eV to 80 MeV (Table C.5), and for protons and alpha particles of 10 ke V to 100 Me V (Tables C.6 and C.7)11. All of the tables give the absolute material constants for ICRU tissue (ICRU, 1964), and, for all other compounds and mixtures, the relative material constants, relative to ICRU tissue. This was done in order to allow for a quick orientation as to the interactions and energy ranges for which a particular compound or mixture can be regarded as tissue equivalent.
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
There are a number of relationships between microdosimetric quantities and their macroscopic anal... more There are a number of relationships between microdosimetric quantities and their macroscopic analogues. Some of these are of a general nature and follow from the definition of the quantity or can be derived mathematically. Others are restricted to a particular geometry or utilize a specific approximation, such as the continuous slowing down approximation (csda). When such restrictions are present, it will be explicitly noted; otherwise, the relationships can be assumed to be generally valid. All formulae given here, and others, are tabulated in a summary of microdosimetric quantities by Kellerer and Rossi (1970). Definition of the relevant variables, energy imparted. f, specific energy, z, and lineal energy, y , as well as the definition of their distributions have been given in Section 2 and will not be repeated here.
Journal of the International Commission on Radiation Units and Measurements, 1983
Experiments and calculations of microd08imetric spectra play complementary roles. The degree of a... more Experiments and calculations of microd08imetric spectra play complementary roles. The degree of agreement between experiment and theory serves as a test of the validity of both. Each can extend the other-theory by calculation of spectra for wide ranges of parameters impossible or difficult to measure, experiment by measurement of spectra where input data for calculation is not available. With currently available methods, microdosimetric distributions of ionization can be measured only for simulated volumes of unit density material having linear dimensions larger than about 0.3 ~m. In addition, the standard deviation of the distribution of ion yield can be determined experimentally for volume sizes down to 10 nm. These experimental techniques can be applied without major correction to gamma-rays of 50 keV to 5 MeV, thermal neutrons, and fast neutrons below 10 Me V. However, outside of this energy range, and for other types of radiations, corrections may be necessary, in particular, for insufficient tissue equivalence. If the primary cross sections are known for these energies, calculations are probably more accurate than measurements. Once adequate mathematical formulations and algorithms have been developed, it is less time consuming to calculate lineal energy spectra for a large variety of physical conditions, for example, different energies for the incident radiation, different cavity sizes and different composition for the wall and the gas, than to measure them. However, it must always be kept in mind that calculations may involve simplifying assumptions, which may not yield adequately accurate results. In addition to the description of the methods for calculating lineal energy spectra, this chapter will also deal with the methods of calculating f(z) as a function of absorbed dose. Finally, the convolution of f(z) for inhomogeneously distributed radiation sources will be considered. Monte-Carlo computer programs which permit detailed simulation of structured charged-particle tracks are dealt with in Section 4.3.
Journal of the International Commission on Radiation Units and Measurements, 1983
In analytical calculations, the cada is applied and it is assumed that the charged particles prod... more In analytical calculations, the cada is applied and it is assumed that the charged particles produced travel in straight lines. Formulae for the single-event distributions of energy imparted that result with this assumption will be given for one type of particle; the generalization to a mixed field of different particles is evident. Important auxiliary functions are the chord length distributions that result from the random transversal of convex volumes. Kellerer (1971b) discusses two different kinds of randomness relevant in the present context: Mean free path randomness (p.-randomness). A chord of a convex body is dermed by a point in Euclidian space and a direction. The point and the direction are from independent uniform distributions. This randomness results if the convex body is exposed to a uniform isotropic field of straight infinite tracks. Internal source randomness (i-randomness). A segment is dermed by a point in the interior of a convex body and a direction. The point and the direction are from independent uniform distributions. This i-randomness is what one obtains if the interior of the body is a uniform source of straight particle tracks. The probability densities for p.-randomness, I,. (I), and for i-randomness, Ii (l), are related by fi(l) = t So '" I I,.(x) dx, (E.l)
Journal of the International Commission on Radiation Units and Measurements, 1983
Advances in Space Research, 1994
We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we... more We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a 'second' radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements, 1992
Journal of the International Commission on Radiation Units and Measurements
Most counters in use today are variations and modifications of the original Rossi counter (Rossi ... more Most counters in use today are variations and modifications of the original Rossi counter (Rossi and Rosenzweig, 1955a, 1955b) developed at the Radiological Research Laboratories of Columbia University. For a review of the theory and practice of proportional counter operation see, for example, Emery (1966) or Franzen and Cochran (1962). Section 5 of this report contains a discussion of the practical application of proportional counters to microdosimetry. This Appendix will be concerned with some of the important technical details relating to construction.
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
Journal of the International Commission on Radiation Units and Measurements, 1983
This appendix is a compilation of representative published values of dose-mean lineal energy, YD,... more This appendix is a compilation of representative published values of dose-mean lineal energy, YD, and of frequency-mean lineal energy, YF. It does not pretend to be exhaustive. The large number of variables involved in the experimental determinations of y spectra, e.g., volume size, type of counter, experimental conditions, quality of the beam, etc., influences the mean values. Calculations require parameters, such as cross sections, stopping power etc., which may cause discrepancies between the results of different authors. As indicated in Section 5, the systematic uncertainty in the experimental determination of YF may reach ±30%, mainly related to the extrapolation method used. For this reason, experimental YF values are not given here. The maximal systematic uncertainty one can expect on YD determinations may be estimated at ±10% if the irradiation conditions are identical. But, as irradiation conditions may vary, the values given in the tabulation should be taken only as an indication of the possible range of YD for a given site size and a given particle energy. Figure F.1 gives the variation ofYD as a function of photon energy for different site sizes. Figures F.2 and F.3 show the variation ofYD for 60CO gamma rays with simulated size down to about 0.3 J,Lm. Data points for smaller object sizes can be found in the literature, for instance, for x rays in Forsberg et al. (1978) and for 6OCO 'Y rays in Forsberg and Lindborg (1981). Figure F.4 illustrates the ratios (€lEo) and (tl/Eo2)(EoIt'J calculated by Berger (1974) for monoenergetic electrons of energy
Journal of the International Commission on Radiation Units and Measurements, 1983
The historical background, concepts, fundamentals, and techniques of microdosimetry have been rev... more The historical background, concepts, fundamentals, and techniques of microdosimetry have been reviewed in the first six chapters of this report. This section is concerned with a description of some of the conceptUal and practical methodology useful in the interpretation of a microdosimetric spectrum. It is the intent to set forth in this section the fundamental principles underlying the composition of microdosimetric spectra, in such a way that these principles can be applied to a variety of circumstances. The large number of variables involved. in the ~ormation of any given spectrum, e.g., volume SIZe, particle type, and various statistical factors discussed in Section 5, in general, precludes trivial ic;ientifications. But if some of these factors are known , an understanding of fundamentals may allow an estimate of others. Such interpretation is essential for many applications of microdosimetry (see Section 8). Figure 7.1 is an example which illustrates some of the general features of microdosimetric spectra for photons and neutrons of differing energies. Of special interest is the wide range of lineal energies involved and the changes of shape with energy. The greater part of this section deals with the composition and interpretation of single-event spectra which result from experiments with proportional counters or from calculation. The principles underlying the production of such a spectrum in terms of contributions from a single type of particle of fixed energy are outlined, and then the contributions of different particles and different energies are considered. Examples of interpretation of some important radiation modalities are then shown and discussed. Finally, the last part of this section deals with formation and interpretation of multiple-event, i.e., dose-dependent spectra.