Abstract
For intensity‐modulated radiation therapy, evaluation of the measured dose against the treatment planning calculated dose is essential in the context of patient‐specific quality assurance. The complexity of volumetric arc radiotherapy delivery attributed to its dynamic and synchronization nature require new methods and potentially new tools for the quality assurance of such techniques. In the present study, we evaluated and compared the dosimetric performance of EDR2 film and three other commercially available quality assurance devices: IBA I'MatriXX array, PTW Seven29 array and the Delta 4 array. The evaluation of these dosimetric systems was performed for RapidArc and IMRT deliveries using a Varian NovalisTX linear accelerator. The plans were generated using the Varian Eclipse treatment planning system. Our results showed that all four QA techniques yield equivalent results. All patient QAs passed our institutional clinical criteria of gamma index based on a 3% dose difference and 3 mm distance to agreement. In addition, the Bland‐Altman analysis was performed which showed that all the calculated gamma values of all three QA devices were within 5% from those of the film. The results showed that the four QA systems used in this patient‐specific IMRT QA analysis are equivalent. We concluded that the dosimetric systems under investigation can be used interchangeably for routine patient specific QA.PACS numbers: 87.55.Qr, 87.56.Fc
Highlights
The aim of radiotherapy is to maximize dose to the tumor while, at the same time, minimize the dose to the organs at risk
One of the methods to realize this goal is by modulating the intensity within each beam, known as intensity-modulated radiation therapy (IMRT)
IMRT is an extension of 3D conformal radiation therapy (3DCRT) in which only the beam apertures conform to the projected shape of the target.[1]
Summary
The aim of radiotherapy is to maximize dose to the tumor while, at the same time, minimize the dose to the organs at risk. A more complex method of delivering nonuniform intensity beams is by introducing gantry rotation while modulating the intensity of the field. This technique is called intensity-modulated arc herapy[4] (IMAT). RapidArc (Varian Medical Systems, Palo Alto, CA) has become available for the treatment planning and delivery of the arc-dynamic IMRT It incorporates capabilities such as variable dose-rate, variable gantry speed, and fast dynamic multileaf collimators (DMLC), to optimize dose conformity, delivery efficiency, accuracy and reliability.[6] RapidArc is regarded as a complex treatment because the leaves of the MLC are continuously moving, and the gantry speed and dose rate are variably modulated. Because of the increased degrees of modulation present in RapidArc delivery, a robust QA program is necessary, allowing for an efficient and effective way to perform quality assurance on a routine basis.[7]
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