Güngör Görkem, Aydın Gökhan, Mustafayev Teuta Zoto, Özyar Enis
Department of Medical Physics, Medipol University Institute of Health Sciences, Istanbul, Turkey.
Department of Radiation Oncology, Acıbadem Mehmet Ali Aydınlar University School of Medicine, Istanbul, Turkey.
J Appl Clin Med Phys. 2019 Feb;20(2):13-23. doi: 10.1002/acm2.12522. Epub 2019 Jan 10.
The electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detectors (SS) for electron beam energies generated by LIAC and compare with the output factor of Monte Carlo model (MC) in order to determine the adequate detectors for LIAC .
The OFs were measured for 6, 8, 10, and 12 MeV electron energies with PTW 23343 Markus, PTW 34045 Advanced Markus, PTW 34001 Roos, IBA PPC05, IBA PPC40, IBA NACP-02, PTW 31010 Semiflex, PTW 31021 Semiflex 3D, PTW 31014 Pinpoint, PTW 60017 Diode E, PTW 60018 Diode SRS, SNC Diode EDGE, and PTW 60019 micro Diamond detectors. Ion recombination factors (k ) of IC were measured for all applicator sizes and OFs were corrected according to k . The measured OFs were compared with Monte Carlo output factors (OF ).
The measured OFs of IBA PPC05, PTW Advanced Markus, PTW Pinpoint, PTW microDiamond, and PTW Diode E detectors are in good agreement with OF . The maximum deviations of IBA PPC05 OFs to OF are -1.6%, +1.5%, +1.5%, and +2.0%; for PTW Advanced Markus +1.0%, +1.5%, +2.0%, and +2.0%; for PTW Pinpoint +2.0%, +1.6%, +4.0%, and +2.0%; for PTW microDiamond -1.6%, +2%, +1.1%, and +1.0%; and for PTW Diode E -+1.7%, +1.7%, +1.3%, and +2.5% for 6, 8, 10, and 12 MeV, respectively. PTW Roos, PTW Markus, IBA PPC40, PTW Semiflex, PTW Semiflex 3D, SNC Diode Edge measured OFs with a maximum deviation of +5.6%, +4.5%, +5.6%, +8.1%, +4.8%, and +9.6% with respect to OF , while PTW Diode SRS and IBA NACP-02 were the least accurate (with highest deviations -37.1% and -18.0%, respectively).
The OFs results of solid state detectors PTW microDiamond and PTW Diode E as well as the ICs with small electrode spacing distance such as IBA PPC05, PTW Advanced Markus and PTW Pinpoint are in excellent agreement with OF . The measurements of the other detectors evaluated in this study are less accurate, thus they should be used with caution. Particularly, PTW Diode SRS and IBA NACP-02 are not suitable and their use should be avoided in relative dosimetry measurements under high dose per pulsed (DPP) electron beams.
移动术中放射治疗（IORT）加速器LIAC的电子能量特性与常用的直线加速器不同，因此一些常用探测器可能给出不太准确的结果。本研究的目的是评估几种电离室（IC）和固态探测器（SS）对LIAC产生的电子束能量的输出因子（OF），并与蒙特卡罗模型（MC）的输出因子进行比较，以确定适用于LIAC的探测器。
使用PTW 23343 Markus、PTW 34045 Advanced Markus、PTW 34001 Roos、IBA PPC05、IBA PPC40、IBA NACP - 02、PTW 31010 Semiflex、PTW 31021 Semiflex 3D、PTW 31014 Pinpoint、PTW 60017 Diode E、PTW 60018 Diode SRS、SNC Diode EDGE和PTW 60019微型金刚石探测器，测量6、8、10和12 MeV电子能量的OF。测量了所有施源器尺寸下IC的离子复合因子（k），并根据k对OF进行校正。将测量的OF与蒙特卡罗输出因子（OF）进行比较。
IBA PPC05、PTW Advanced Markus、PTW Pinpoint、PTW微型金刚石和PTW Diode E探测器测量的OF与OF吻合良好。IBA PPC05的OF与OF的最大偏差分别为6、8、10和12 MeV时的 - 1.6%、+1.5%、+1.5%和 + 2.0%；PTW Advanced Markus为 + 1.0%、+1.5%、+2.0%和 + 2.0%；PTW Pinpoint为 + 2.0%、+1.6%、+4.0%和 + 2.0%；PTW微型金刚石为 - 1.6%、+2%、+1.1%和 + 1.0%；PTW Diode E为 - + 1.7%、+1.7%、+1.3%和 + 2.5%。PTW Roos、PTW Markus、IBA PPC40、PTW Semiflex、PTW Semiflex 3D、SNC Diode Edge测量的OF与OF的最大偏差分别为 + 5.6%、+4.5%、+5.6%、+8.1%、+4.8%和 + 9.6%，而PTW Diode SRS和IBA NACP - 02最不准确（最大偏差分别为 - 37.1%和 - 18.0%）。
固态探测器PTW微型金刚石和PTW Diode E以及电极间距小的IC（如IBA PPC05、PTW Advanced Markus和PTW Pinpoint）的OF结果与OF吻合极佳。本研究中评估的其他探测器的测量不太准确，因此应谨慎使用。特别是，PTW Diode SRS和IBA NACP - 02不合适，在高脉冲剂量（DPP）电子束下的相对剂量测量中应避免使用。
