Abstract
With the commercial introduction of the Varian RapidArc, a new modality for treatment planning and delivery, the need has arisen for consistent and efficient techniques for performing patient‐specific quality assurance (QA) tests. In this paper we present our methodology for a RapidArc treatment plan QA procedure. For our measurements we used a 2D diode array (MapCHECK) embedded at 5 cm water equivalent depth in MapPHAN 5 phantom and an Exradin A16 ion chamber placed in six different positions in a cylindrical homogeneous phantom (QUASAR). We also checked the MUs for the RapidArc plans by using independent software (RadCalc). The agreement between Eclipse calculations and MapCHECK/MapPHAN 5 measurements was evaluated using both absolute distance‐to‐agreement (DTA) and gamma index with 10% dose threshold (TH), 3% dose difference (DD), and 3 mm DTA. The average agreement was 94.4% for the DTA approach and 96.3% for the gamma index approach. In high‐dose areas, the discrepancy between calculations and ion chamber measurements using the QUASAR phantom was within 4.5% for prostate cases. For the RadCalc calculations, we used the average SSD along the arc; however, for some patients the agreement for the MUs obtained with RadCalc versus Eclipse was inadequate (discrepancy>5%). In these cases, the plan was divided into partial arc plans so that RadCalc could perform a better estimation of the MUs. The discrepancy was further reduced to within ~4% using this approach. Regardless of the variation in prescribed dose and location of the treated areas, we obtained very good results for all patients studied in this paper.PACS number: 87.55.Qr
Highlights
RapidArc (Varian Medical Systems, Palo Alto, CA) is a new treatment planning and delivery approach based on a volumetric intensity-modulated single arc technique originally investigated by Otto.[1]
In our clinic for routine intensity-modulated radiation therapy (IMRT) quality assurance (QA) we measure each field individually in beam’s eye view (BEV), using MapCHECK version 4.1.1 (Sun Nuclear Corp.), with added buildup for comparison with planar doses at a depth of 5 cm water equivalent
The dose-volume histogram (DVH) was analyzed for tumor and critical structures to check if all objectives were met
Summary
RapidArc (Varian Medical Systems, Palo Alto, CA) is a new treatment planning and delivery approach based on a volumetric intensity-modulated single arc technique originally investigated by Otto.[1]. The Varian RapidArc has become available for the treatment planning and delivery of arc-dynamic IMRT. The arc optimization algorithm, PRO (Progressive Resolution Optimizer), optimizes leaf position, dose rate and gantry speed. In RapidArc version 8.5, the optimization begins with 10 control points, gradually increasing them (up to a maximum of 177). Both the treatment planning and linac systems must incorporate special capabilities such as variable dose rate, variable gantry speed and dynamic MLC movement in order to make a RapidArc plan deliverable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
