In principle, both kerma and absorbed dose can be determined for any material at any energy. Given the considerations noted above regarding secondaryphoton contributions and charged-particle equilibrium (CPE), it is not surprising that the relationship between kerma and absorbed dose changes significantly with energy and material. Because of the very limited beam penetration and the relatively low absorbed-dose rates involved, absorbed dose is very difficult to realize directly for kilovoltage x rays, although a few water calorimeter standards have been developed (see, e.g., de Prez and de Pooter, 2008; Krauss et al., 2012; Rapp et al., 2013). Most primary standards for these radiations are based on kerma, in particular on the determination of the air kerma using a free-air ionization chamber. At Co g-ray energies, the need for CPE would require a prohibitively large free-air chamber, and cavity-ionization chambers are used as primary standards. In more recent years, the direct determination of absorbed dose by graphite and water calorimetry has produced standards with an overall uncertainty that matches, and in some cases reduces, that derived from a determination of air kerma. Nevertheless, air kerma for Co g rays remains a very important reference quantity, particularly for standards laboratories. At the high energies produced by particle accelerators, the determination of air kerma free in air in these beams is no longer used to determine absorbed dose. In more recent years, absorbed-dose standards at high energies have been used, either directly for instrument calibrations or more commonly to determine values for correction factors that convert an ionization-chamber absorbed-dose calibration for Co g rays for use at higher energies (McEwen, 2010; Seuntjens et al., 2000). Several review articles describing the standards used for radiation dosimetry have been published in a special issue of Metrologia (Sharpe, 2009).
原则上，对于任何能量的任何物质，可玛和吸收剂量都可以测定。考虑到上述关于二次光子贡献和带电粒子平衡(CPE)的考虑，kerma和吸收剂量之间的关系随着能量和物质的变化而显著变化就不足为奇了。由于光束穿透非常有限，所涉及的吸收剂量率相对较低，因此很难直接实现千伏x射线的吸收剂量，尽管已经制定了一些水量热计标准(例如，见de Prez和de Pooter, 2008;Krauss等人，2012;Rapp et al.， 2013)。这些辐射的大多数主要标准是基于克尔玛，特别是使用自由空气电离室测定空气克尔玛。在Co射线能量下，对CPE的需求将需要一个大得令人望而却步的自由空气室，而空腔电离室被用作主要标准。近年来，用石墨和水量热法直接测定吸收剂量所产生的标准，其总体不确定度与空气热值测定所产生的不确定度相当，在某些情况下甚至有所降低。尽管如此，对于一氧化碳射线，空气温度仍然是一个非常重要的参考量，特别是对于标准实验室。在粒子加速器产生的高能量下，这些光束中空气中游离空气克尔玛的测定不再用于测定吸收剂量。近年来，高能量吸收剂量标准已被直接用于仪器校准，或更常见地用于确定校正因子的值，这些校正因子将电离室吸收剂量校准的Co g射线转换为高能量使用(McEwen, 2010;Seuntjens et al.， 2000)。《计量学》(Sharpe, 2009)的特刊上发表了几篇描述辐射剂量学标准的评论文章。
{"title":"3. Realization of Quantities by Primary Standards Laboratories","authors":"","doi":"10.1093/jicru_ndw037","DOIUrl":"https://doi.org/10.1093/jicru_ndw037","url":null,"abstract":"In principle, both kerma and absorbed dose can be determined for any material at any energy. Given the considerations noted above regarding secondaryphoton contributions and charged-particle equilibrium (CPE), it is not surprising that the relationship between kerma and absorbed dose changes significantly with energy and material. Because of the very limited beam penetration and the relatively low absorbed-dose rates involved, absorbed dose is very difficult to realize directly for kilovoltage x rays, although a few water calorimeter standards have been developed (see, e.g., de Prez and de Pooter, 2008; Krauss et al., 2012; Rapp et al., 2013). Most primary standards for these radiations are based on kerma, in particular on the determination of the air kerma using a free-air ionization chamber. At Co g-ray energies, the need for CPE would require a prohibitively large free-air chamber, and cavity-ionization chambers are used as primary standards. In more recent years, the direct determination of absorbed dose by graphite and water calorimetry has produced standards with an overall uncertainty that matches, and in some cases reduces, that derived from a determination of air kerma. Nevertheless, air kerma for Co g rays remains a very important reference quantity, particularly for standards laboratories. At the high energies produced by particle accelerators, the determination of air kerma free in air in these beams is no longer used to determine absorbed dose. In more recent years, absorbed-dose standards at high energies have been used, either directly for instrument calibrations or more commonly to determine values for correction factors that convert an ionization-chamber absorbed-dose calibration for Co g rays for use at higher energies (McEwen, 2010; Seuntjens et al., 2000). Several review articles describing the standards used for radiation dosimetry have been published in a special issue of Metrologia (Sharpe, 2009).","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"16 1","pages":"15 - 20"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88237752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This Section presents the analyses that support new recommendations for the numerical values, and the associated uncertainties, of the key parameters considered in this Report. These key data include the mean excitation energies for air, Iair, and for graphite, Ig, that are needed in the determination of stopping-power ratios, the average energy to create an ion pair in air, Wair, which is needed for the determination of air kerma, and the mean excitation energy for liquid water, Iw, which is central to calculations that support charged-particle therapy and is important for certain factors entering in the determination of absorbed dose in water. Recommendations are also given for the humidity correction factor, kh, for air-filled ionization chambers, the ferric ion yield, G(Fe3þ), required for Fricke dosimetry and the heat defect, h, for graphite and water calorimetry. Data for kW, the correction in photon and electron beams at low energies for the deviation of Wair from the high-energy value, and for kii, the correction to the measured charge due to the ion pairs created by an incident photon, are also summarized.
{"title":"5. Recommended Values for Key Data","authors":"","doi":"10.1093/jicru_ndw038","DOIUrl":"https://doi.org/10.1093/jicru_ndw038","url":null,"abstract":"This Section presents the analyses that support new recommendations for the numerical values, and the associated uncertainties, of the key parameters considered in this Report. These key data include the mean excitation energies for air, Iair, and for graphite, Ig, that are needed in the determination of stopping-power ratios, the average energy to create an ion pair in air, Wair, which is needed for the determination of air kerma, and the mean excitation energy for liquid water, Iw, which is central to calculations that support charged-particle therapy and is important for certain factors entering in the determination of absorbed dose in water. Recommendations are also given for the humidity correction factor, kh, for air-filled ionization chambers, the ferric ion yield, G(Fe3þ), required for Fricke dosimetry and the heat defect, h, for graphite and water calorimetry. Data for kW, the correction in photon and electron beams at low energies for the deviation of Wair from the high-energy value, and for kii, the correction to the measured charge due to the ion pairs created by an incident photon, are also summarized.","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"71 1","pages":"31 - 48"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75946170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"3. Realization of Quantities by Primary Standards Laboratories","authors":"","doi":"10.1093/jicru/ndw037","DOIUrl":"https://doi.org/10.1093/jicru/ndw037","url":null,"abstract":"","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"15-20"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/jicru/ndw037","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67910021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Charged-particle stopping powers have been treated in detail in ICRU Report 37 (ICRU, 1984a), Report 49 (ICRU, 1993), and Report 73 (ICRU, 2005; Sigmund et al., 2009). In the present Report, consideration has been confined to electrons (and positrons), protons, and a particles for three key materials: graphite, air, and liquid water. Additionally, information on C ions in these materials has been included in recognition of their increasing use in radiation therapy. The stopping power quantifies the average energy loss per pathlength of charged particles in matter. In principle, the stopping power consists of three contributions, namely the electronic (or collision), the radiative, and the nuclear stopping power. The nuclear stopping power is negligible for electrons; it can be significant for light and heavy ions (ICRU, 1993; 2005), but only at rather low kinetic energies. A recommendation issued jointly by the ICRU and IAEA (Wambersie et al., 2004) calls “light ions” those nuclei with an atomic number equal to, or smaller than, that of neon nuclei (Z 1⁄4 10), leaving the name of “heavy ions” to all heavier nuclei. Results for the nuclear stopping power from ICRU Report 49 (1993) will be included in the tables presented in this Report for completeness. The radiative stopping power for electrons and positrons can be quite significant; for light and heavy ions, it is smaller to first approximation by a factor of (me/M) , where me is the rest mass of the electron and M the rest mass of the incident ion. Thus, the radiative stopping power can be ignored for protons and heavier ions at the kinetic energies considered in this Report.
ICRU第37号报告(ICRU, 1984a)、第49号报告(ICRU, 1993)和第73号报告(ICRU, 2005;Sigmund et al.， 2009)。在本报告中，考虑仅限于三种关键材料的电子(和正电子)、质子和粒子:石墨、空气和液态水。此外，这些材料中有关C离子的信息已被包括在内，以认识到它们在放射治疗中的应用日益增加。停止功率量化了物质中带电粒子每路径长度的平均能量损失。原则上，停止功率由三种贡献组成，即电子(或碰撞)，辐射和核停止功率。对于电子来说，核的停止力可以忽略不计;它对轻离子和重离子可能很重要(ICRU, 1993年;2005)，但只有在相当低的动能。ICRU和IAEA联合发布的一项建议(Wambersie et al.， 2004)将原子序数等于或小于氖核(Z 1 / 4 10)的原子核称为“轻离子”，而将“重离子”的名称留给所有较重的原子核。ICRU第49号报告(1993)中关于核停止力的结果将列入本报告所列的表格中，以确保完整性。电子和正电子的辐射阻止能力是相当显著的;对于轻离子和重离子，它比第一次近似小(me/M)，其中me是电子的静止质量，M是入射离子的静止质量。因此，在本报告所考虑的动能下，质子和较重的离子的辐射阻止能力可以忽略不计。
{"title":"4. Charged-Particle Stopping Powers and Related Quantities","authors":"","doi":"10.1093/jicru_ndw031","DOIUrl":"https://doi.org/10.1093/jicru_ndw031","url":null,"abstract":"Charged-particle stopping powers have been treated in detail in ICRU Report 37 (ICRU, 1984a), Report 49 (ICRU, 1993), and Report 73 (ICRU, 2005; Sigmund et al., 2009). In the present Report, consideration has been confined to electrons (and positrons), protons, and a particles for three key materials: graphite, air, and liquid water. Additionally, information on C ions in these materials has been included in recognition of their increasing use in radiation therapy. The stopping power quantifies the average energy loss per pathlength of charged particles in matter. In principle, the stopping power consists of three contributions, namely the electronic (or collision), the radiative, and the nuclear stopping power. The nuclear stopping power is negligible for electrons; it can be significant for light and heavy ions (ICRU, 1993; 2005), but only at rather low kinetic energies. A recommendation issued jointly by the ICRU and IAEA (Wambersie et al., 2004) calls “light ions” those nuclei with an atomic number equal to, or smaller than, that of neon nuclei (Z 1⁄4 10), leaving the name of “heavy ions” to all heavier nuclei. Results for the nuclear stopping power from ICRU Report 49 (1993) will be included in the tables presented in this Report for completeness. The radiative stopping power for electrons and positrons can be quite significant; for light and heavy ions, it is smaller to first approximation by a factor of (me/M) , where me is the rest mass of the electron and M the rest mass of the incident ion. Thus, the radiative stopping power can be ignored for protons and heavier ions at the kinetic energies considered in this Report.","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"8 1","pages":"21 - 30"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73649081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"5. Recommended Values for Key Data","authors":"","doi":"10.1093/jicru/ndw038","DOIUrl":"https://doi.org/10.1093/jicru/ndw038","url":null,"abstract":"","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"31-48"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/jicru/ndw038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67910018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"4. Charged-Particle Stopping Powers and Related Quantities","authors":"","doi":"10.1093/jicru/ndw031","DOIUrl":"https://doi.org/10.1093/jicru/ndw031","url":null,"abstract":"","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"21-30"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/jicru/ndw031","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67910019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"1. Introduction","authors":"","doi":"10.1093/jicru/ndw034","DOIUrl":"https://doi.org/10.1093/jicru/ndw034","url":null,"abstract":"","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"5-8"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/jicru/ndw034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67910022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"2. Definitions of Basic Quantities and Terms","authors":"","doi":"10.1093/jicru/ndw032","DOIUrl":"https://doi.org/10.1093/jicru/ndw032","url":null,"abstract":"","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"9-14"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/jicru/ndw032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67910020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fluence, F, is given by F 1⁄4 dN=da, where dN is the number of particles incident on a sphere of cross-sectional area da. The energy fluence, C, is given by C 1⁄4 dR=da, where dR is the radiant energy incident on a sphere of cross-sectional area da. The radiant energy, R, is the energy (excluding rest energy) of the particles that are emitted, transferred, or received. The distributions, FE and CE, of the fluence and energy fluence with respect to energy are given by FE 1⁄4 dF/dE, and CE 1⁄4 dC/dE, where dF is the fluence of particles of energy between E and E þ dE, and dC is their energy fluence. The relationship between the two distributions is given by CE 1⁄4 EFE.
{"title":"2. Definitions of Basic Quantities and Terms","authors":"","doi":"10.1093/jicru_ndw032","DOIUrl":"https://doi.org/10.1093/jicru_ndw032","url":null,"abstract":"The fluence, F, is given by F 1⁄4 dN=da, where dN is the number of particles incident on a sphere of cross-sectional area da. The energy fluence, C, is given by C 1⁄4 dR=da, where dR is the radiant energy incident on a sphere of cross-sectional area da. The radiant energy, R, is the energy (excluding rest energy) of the particles that are emitted, transferred, or received. The distributions, FE and CE, of the fluence and energy fluence with respect to energy are given by FE 1⁄4 dF/dE, and CE 1⁄4 dC/dE, where dF is the fluence of particles of energy between E and E þ dE, and dC is their energy fluence. The relationship between the two distributions is given by CE 1⁄4 EFE.","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"31 1","pages":"13 - 9"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81105320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
New tables of stopping powers and ranges have been developed, using the methods described earlier, for the three materials of interest in this Report: air, graphite, and liquid water. The main differences in results from those in the earlier ICRU tabulations are due to the change in I values. However, the choice of the grain density for graphite, as indicated earlier, also affects the mass electronic stopping power through the density-effect correction. Estimates of the uncertainties associated with the tabulated quantities are given below, generally based on the expected accuracy of either the underlying theoretical treatment or the measured data used to extend coverage of the heavy charged particles to low energies. Uncertainties in the stopping powers and ranges due to uncertainties associated with the I values can be determined from the coefficients of relative change given in the tables. This was done in ICRU Report 37 (ICRU, 1984a) and facilitates also the determination of the quantities for a somewhat different choice of I value. The coefficients are given in terms of @(log X)/@(log I), where X can be the mass electronic stopping power, Sel/r, the csda range, rr0, and—in the case of electrons and positrons—the radiation yield, Y. The main results are given to four significant figures, more than are warranted by the expected accuracy of the evaluations, in order to facilitate smooth interpolation. Based on practices used in the development of these tables, log-log interpolation is recommended, using natural cubic splines fitted to ln X as a function of ln T, where X is the variable of interest.
{"title":"Appendix. Stopping Power and Range Tables for Charged Particles","authors":"","doi":"10.1093/jicru_ndw030","DOIUrl":"https://doi.org/10.1093/jicru_ndw030","url":null,"abstract":"New tables of stopping powers and ranges have been developed, using the methods described earlier, for the three materials of interest in this Report: air, graphite, and liquid water. The main differences in results from those in the earlier ICRU tabulations are due to the change in I values. However, the choice of the grain density for graphite, as indicated earlier, also affects the mass electronic stopping power through the density-effect correction. Estimates of the uncertainties associated with the tabulated quantities are given below, generally based on the expected accuracy of either the underlying theoretical treatment or the measured data used to extend coverage of the heavy charged particles to low energies. Uncertainties in the stopping powers and ranges due to uncertainties associated with the I values can be determined from the coefficients of relative change given in the tables. This was done in ICRU Report 37 (ICRU, 1984a) and facilitates also the determination of the quantities for a somewhat different choice of I value. The coefficients are given in terms of @(log X)/@(log I), where X can be the mass electronic stopping power, Sel/r, the csda range, rr0, and—in the case of electrons and positrons—the radiation yield, Y. The main results are given to four significant figures, more than are warranted by the expected accuracy of the evaluations, in order to facilitate smooth interpolation. Based on practices used in the development of these tables, log-log interpolation is recommended, using natural cubic splines fitted to ln X as a function of ln T, where X is the variable of interest.","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"34 1","pages":"79 - 97"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80647931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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