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Improving Dose Determination Accuracy in Nonstandard Fields of the Varian TrueBeam Accelerator.

机译：改善瓦里安TrueBeam加速器非标准领域的剂量确定精度。

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摘要

In recent years, the use of flattening-filter-free (FFF) linear accelerators in radiation-based cancer therapy has gained popularity, especially for hypofractionated treatments (high doses of radiation given in few sessions). However, significant challenges to accurate radiation dose determination remain. If physicists cannot accurately determine radiation dose in a clinical setting, cancer patients treated with these new machines will not receive safe, accurate and effective treatment. In this study, an extensive characterization of two commonly used clinical radiation detectors (ionization chambers and diodes) and several potential reference detectors (thermoluminescent dosimeters, plastic scintillation detectors, and alanine pellets) has been performed to investigate their use in these challenging, nonstandard fields. From this characterization, reference detectors were identified for multiple beam sizes, and correction factors were determined to improve dosimetric accuracy for ionization chambers and diodes. A validated computational (Monte Carlo) model of the TrueBeam(TM) accelerator, including FFF beam modes, was also used to calculate these correction factors, which compared favorably to measured results. Small-field corrections of up to 18 % were shown to be necessary for clinical detectors such as microionization chambers. Because the impact of these large effects on treatment delivery is not well known, a treatment planning study was completed using actual hypofractionated brain, spine, and lung treatments that were delivered at the UW Carbone Cancer Center. This study demonstrated that improperly applying these detector correction factors can have a substantial impact on patient treatments. This thesis work has taken important steps toward improving the accuracy of FFF dosimetry through rigorous experimentally and Monte-Carlo-determined correction factors, the validation of an important published protocol (TG-51) for use with FFF reference fields, and a demonstration of the clinical significance of small-field correction factors. These results will facilitate the safe, accurate and effective use of this treatment modality in the clinic.
机译：近年来，在基于放射的癌症治疗中使用无扁平过滤器（FFF）的线性加速器已变得越来越普及，尤其是对于超分割治疗（很少使用高剂量放射治疗）。然而，精确辐射剂量确定仍然面临重大挑战。如果物理学家在临床环境中无法准确确定辐射剂量，那么使用这些新机器治疗的癌症患者将无法获得安全，准确和有效的治疗。在这项研究中，已对两种常用的临床放射线检测器（电离室和二极管）和几种潜在的参考检测器（热发光剂量计，塑料闪烁检测器和丙氨酸颗粒）进行了广泛的表征，以研究它们在这些挑战性非标准领域中的用途。 。通过这种表征，可以确定多种光束尺寸的参考检测器，并确定校正因子以提高电离室和二极管的剂量学准确性。 TrueBeam™加速器的经过验证的计算（Monte Carlo）模型（包括FFF光束模式）也用于计算这些校正因子，与测量结果相比具有优势。对于诸如微电离室之类的临床检测器，必须进行高达18％的小视场校正。由于这些大效应对治疗的影响尚不为人所知，因此，使用UW Carbone癌症中心提供的实际的低等脑，脊柱和肺部治疗完成了治疗计划研究。这项研究表明，不正确地应用这些检测器校正因子可能会对患者的治疗产生重大影响。本论文的工作已采取重要步骤，通过严格的实验和蒙特卡洛确定的校正因子提高FFF剂量测定的准确性，验证了用于FFF参考领域的重要出版协议（TG-51），并证明了小视野矫正因子的临床意义。这些结果将有助于在临床上安全，准确和有效地使用这种治疗方式。

著录项

  • 作者

    Hyun, Megan A.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Physics.;Medicine.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 190 p.
  • 总页数 190
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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