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首页> 外文期刊>Medical Physics >Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols.
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Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols.

机译：在吸收剂量方案的背景下，使用固体体模的吸收剂量与水的参考剂量法。

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摘要

For reasons of phantom material reproducibility, the absorbed dose protocols of the American Association of Physicists in Medicine (AAPM) (TG-51) and the International Atomic Energy Agency (IAEA) (TRS-398) have made the use of liquid water as a phantom material for reference dosimetry mandatory. In this work we provide a formal framework for the measurement of absorbed dose to water using ionization chambers calibrated in terms of absorbed dose to water but irradiated in solid phantoms. Such a framework is useful when there is a desire to put dose measurements using solid phantoms on an absolute basis. Putting solid phantom measurements on an absolute basis has distinct advantages in verification measurements and quality assurance. We introduce a phantom dose conversion factor that converts a measurement made in a solid phantom and analyzed using an absorbed dose calibration protocol into absorbed dose to water under reference conditions. We provide techniques to measure and calculate the dose transferfrom solid phantom to water. For an Exradin A12 ionization chamber, we measured and calculated the phantom dose conversion factor for six Solid Water phantoms and for a single Lucite phantom for photon energies between 60Co and 18 MV photons. For Solid Water of certified grade, the difference between measured and calculated factors varied between 0.0% and 0.7% with the average dose conversion factor being low by 0.4% compared with the calculation whereas for Lucite, the agreement was within 0.2% for the one phantom examined. The composition of commercial plastic phantoms and their homogeneity may not always be reproducible and consistent with assumed composition. By comparing measured and calculated phantom conversion factors, our work provides methods to verify the consistency of a given plastic for the purpose of clinical reference dosimetry.
机译：出于幻象材料可再现性的原因，美国医学物理学会（AAPM）（TG-51）和国际原子能机构（IAEA）（TRS-398）的吸收剂量方案已将液态水用作用于参考剂量测定的幻像材料是强制性的。在这项工作中，我们提供了一个使用电离室测量水吸收剂量的正式框架，该电离室根据对水的吸收剂量进行了校准，但以固体幻影进行了辐射。当需要绝对使用固体体模进行剂量测量时，这种框架很有用。绝对地放置实体模型测量在验证测量和质量保证方面具有明显的优势。我们引入了幻象剂量转换因子，该因子将在实物幻象中进行的测量值转换为参考条件下使用吸收剂量校准方案分析的吸收剂量。我们提供测量和计算从固体幻影到水的剂量转移的技术。对于Exradin A12电离室，我们测量并计算了60Co和18 MV光子之间光子能量的六个固体水体模和单个Lucite体模的体模剂量转换因子。对于认证等级的固体水，测得的和计算的因子之间的差异在0.0％到0.7％之间，平均剂量转换因子比计算的低0.4％，而对于Lucite，一个幻影的一致性在0.2％以内检查。商业塑料模型的组成及其同质性可能并不总是可再现的，并且与假定的组成保持一致。通过比较测得的和计算的幻像转换因子，我们的工作提供了用于验证给定塑料一致性的方法，以用于临床参考剂量测定。

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