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ICom - A Communication Interface for Quality Assurance in VMAT Treatment Delivery

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S Nicol

S Nicol*, C Furstoss, W Wierzbicki, P Munger, Hopital Maisonneuve-Rosemont, Montreal, QC

SU-E-T-336 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: To present a VMAT QA tool that uses the iCom messaging interface from Elekta Synergy linear accelerators to record and compare, during treatment, real-time delivery parameters with expected DICOM-RT plan values. These delivery parameters can also be formatted offline into a new DICOM-RT plan, then sent back to Pinnacle to compute the 3D delivered dose distribution.

Method and Materials: In order to evaluate the sensitivity of our QA tool to mechanical errors and to judge their effects on the delivered dose, both static and dynamic QA plans with and without simulated errors in leaf and gantry position were delivered and analyzed. While static plans were delivered to an EPID, dynamic plans were delivered to an ArcCHECK device embedded with its own cavity insert and a Micro-Lion ionizing chamber. To clinically assess the dosimetric accuracy of VMAT deliveries as well as treatment degradation due to machine imprecision, several SRS QA plans were finally delivered to a home made gelatine phantom embedded with small plastic inserts with both TLD and nanoDot dosimeters. To validate our approach, comparisons between calculated (planned and reconstructed) and measured absorbed doses were systematically performed.

Results: First results demonstrated that real-time delivery parameters corresponded well to expected plan values. Simulated errors in leaf and gantry position can easily be detected by our QA tool. Although work is still in progress, these deliberately introduced errors seem to have a negligible impact on delivered dose except for small fields or segments. Results obtained with VMAT plans indicate good agreement between reconstructed and planned dose distributions, as well as with dose measurements in the gelatine phantom.

Conclusions: In this study, we developed a practical QA software solution based on the Elekta iCom interface to perform a) real-time VMAT monitoring and b) a volumetric reconstruction of the delivered dose to assess degradation effects produced by machine imprecision. This approach aims to ensure that all critical aspects of VMAT delivery are properly functioning.

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