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Measurements of photo-neutrons from a medical linear accelerator using CR-39 plastic nuclear track detectors.

机译：使用CR-39塑料核径迹探测器从医用线性加速器中测量光中子。

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摘要

Photo-neutrons are produced when x-ray energies exceed 7 MeV. Photo-neutron production varies depending on x-ray beam energy. CR-39 PNTDs were used in this study to measure the neutron absorbed dose and dose equivalent produced by a Varian Clinac 23EX for x-ray beams of 6 and 18 MVp and with a Varian Trilogy using an x-ray beam of 10 MVp. Neutron absorbed dose and dose equivalent were measured at 100 cm SSD at 0, 20, and 40 cm off-axis from the primary beam in air. Using a polyethylene phantom the neutron absorbed dose and dose equivalent were measured at 100 cm SSD from the top of the phantom at 0, 5, and 10 cm from the surface, in the beam central axis and off-axis distances of 20 and 40 cm at a depth of 10 cm. The neutron absorbed dose and dose equivalent from medical linear accelerators have been measured from the LET spectrum of recoiled tracks produced in the CR-39 PNTDs for high energy neutrons (1-20 MeV) and the neutron dose equivalent for low energy (< 1 MeV) neutrons were measured using TRNDs. In this study, the experimentally measured absorbed dose and dose equivalent from photo-neutrons produced in a common medical linear accelerator operating at energies 10 and 18 MVp range from 0.2 microGy n/Gyx and 2 microSv n/Gyx to 495 microGy n/Gyx and 5500 microSv n/Gyx respectively. The neutron absorbed dose for the 6 MVp x-ray beam was measured to be 0 microGyn/Gyx. Low energy neutrons accounted for less than 1% of the neutron dose equivalent. Those detectors exposed inside of the phantom measured a higher contribution from high LET (> 100 keV/microm) particles than those detectors exposed in air.
机译：X射线能量超过7 MeV时会产生光中子。光中子的产生取决于X射线束能量。 CR-39 PNTD在本研究中用于测量Varian Clinac 23EX对6和18 MVp的X射线束以及Varian Trilogy使用10 MVp的X射线束产生的中子吸收剂量和当量剂量。中子吸收剂量和当量剂量是在距空气中的主光束离轴0、20和40 cm处于100 cm SSD处测量的。使用聚乙烯体模，在离束体中心轴和离轴距离20和40 cm处，距体模顶部距表面0、5和10 cm处100 cm SSD处测量中子吸收剂量和剂量当量在10厘米深处。根据CR-39 PNTD中产生的反冲轨迹的LET谱，对于高能中子（1-20 MeV）和低能（<1 MeV）的中子剂量当量的LET谱测量了医用线性加速器的中子吸收剂量和当量剂量用TRNDs测量中子。在这项研究中，实验测量的吸收剂量和在能量为10和18 MVp的普通医用线性加速器中产生的光中子的吸收当量和剂量当量，范围为0.2 microGy n / Gyx和2 microSv n / Gyx至495 microGy n / Gyx和分别为5500 microSv n / Gyx。 6 MVp X射线束的中子吸收剂量经测量为0 microGyn / Gyx。低能中子占中子剂量当量的不到1％。与暴露在空气中的探测器相比，那些暴露在体模内部的探测器对高LET（> 100 keV / microm）颗粒的贡献更大。

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  • 作者

    Monson, Jonathan Michael.;

  • 作者单位

    Oklahoma State University.;

  • 授予单位 Oklahoma State University.;
  • 学科 Physical therapy.;Nuclear physics and radiation.
  • 学位 M.S.
  • 年度 2014
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:54:09

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