Shahbazi-Gahrouei Daryoush, Saeb Mohsen, Monadi Shahram, Jabbari Iraj
Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Nuclear Engineering, Faculty of Advanced Sciences and Technologies, Isfahan University, Isfahan, Iran.
Adv Biomed Res. 2017 Sep 21;6:117. doi: 10.4103/abr.abr_268_16. eCollection 2017.
Performing audits play an important role in quality assurance program in radiation oncology. Among different algorithms, TiGRT is one of the common application software for dose calculation. This study aimed to clinical implications of TiGRT algorithm to measure dose and compared to calculated dose delivered to the patients for a variety of cases, with and without the presence of inhomogeneities and beam modifiers.
Nonhomogeneous phantom as quality dose verification phantom, Farmer ionization chambers, and PC-electrometer (Sun Nuclear, USA) as a reference class electrometer was employed throughout the audit in linear accelerators 6 and 18 MV energies (Siemens ONCOR Impression Plus, Germany). Seven test cases were performed using semi CIRS phantom.
In homogeneous regions and simple plans for both energies, there was a good agreement between measured and treatment planning system calculated dose. Their relative error was found to be between 0.8% and 3% which is acceptable for audit, but in nonhomogeneous organs, such as lung, a few errors were observed. In complex treatment plans, when wedge or shield in the way of energy is used, the error was in the accepted criteria. In complex beam plans, the difference between measured and calculated dose was found to be 2%-3%. All differences were obtained between 0.4% and 1%.
A good consistency was observed for the same type of energy in the homogeneous and nonhomogeneous phantom for the three-dimensional conformal field with a wedge, shield, asymmetric using the TiGRT treatment planning software in studied center. The results revealed that the national status of TPS calculations and dose delivery for 3D conformal radiotherapy was globally within acceptable standards with no major causes for concern.
开展审核在放射肿瘤学质量保证计划中发挥着重要作用。在不同算法中，TiGRT是剂量计算常用的应用软件之一。本研究旨在探讨TiGRT算法在测量剂量方面的临床意义，并将其与各种病例中输送给患者的计算剂量进行比较，包括有无不均匀性和射束修正装置的情况。
在6兆伏和18兆伏能量的直线加速器（德国西门子ONCOR Impression Plus）审核过程中，采用非均匀体模作为质量剂量验证体模、 Farmer电离室以及作为参考级静电计的PC静电计（美国Sun Nuclear）。使用半CIRS体模进行了7个测试病例。
在两种能量的均匀区域和简单计划中，测量剂量与治疗计划系统计算剂量之间有良好的一致性。发现它们的相对误差在0.8%至3%之间，这在审核中是可接受的，但在非均匀器官（如肺）中，观察到了一些误差。在复杂治疗计划中，当使用楔形物或能量阻挡物时，误差在可接受标准范围内。在复杂射束计划中，测量剂量与计算剂量之间的差异为2%-3%。所有差异均在0.4%至1%之间。
在所研究中心，使用TiGRT治疗计划软件，对于带有楔形物、阻挡物、不对称的三维适形野，在均匀和非均匀体模中，相同类型能量下观察到了良好的一致性。结果显示，三维适形放疗的TPS计算和剂量输送的国内状况在全球范围内处于可接受标准，无需重大担忧。
