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Dosimetric Verification and Preliminary Comparison of Dynamic Wave Arc for SBRT Treatments

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M BURGHELEA1,2,4*, K POELS1 , T GEVAERT1 , K TOURNEL1 , J DHONT1 , C HUNG2 , K ERIKSSON3 , V SIMON4 , M DE RIDDER1 , D Verellen1 , (1) UZ BRUSSEL, Brussels, JETTE, (2) BRAINLAB AG, Munich, FELDKIRCHEN, (3) RAYSEARCH LABORATORIES AB, Stockholm, STOCKHOLM, (4) Babes Bolyai University, Cluj-napoca, CLUJ-NAPOCA,


TU-CD-304-3 (Tuesday, July 14, 2015) 10:15 AM - 12:15 PM Room: 304

Purpose:To evaluate the potential dosimetric benefits and verify the delivery accuracy of Dynamic Wave Arc, a novel treatment delivery approach for the Vero SBRT system.

Methods:Dynamic Wave Arc (DWA) combines simultaneous movement of gantry/ring with inverse planning optimization, resulting in an uninterrupted non-coplanar arc delivery technique. Thirteen SBRT complex cases previously treated with 8-10 conformal static beams (CRT) were evaluated in this study. Eight primary centrally-located NSCLC (prescription dose 4x12Gy or 8x7.5Gy) and five oligometastatic cases (2x2 lesions, 10x5Gy) were selected. DWA and coplanar VMAT plans, partially with dual arcs, were generated for each patient using identical objective functions for target volumes and OARs on the same TPS (RayStation, RaySearch Laboratories). Dosimetric differences and delivery time among these three planning schemes were evaluated. The DWA delivery accuracy was assessed using the Delta4 diode array phantom (ScandiDos AB). The gamma analysis was performed with the 3%/3mm dose and distance-to-agreement criteria.

Results:The target conformity for CRT, VMAT and DWA were 0.95±0.07, 0.96±0.04 and 0.97±0.04, while the low dose spillage gradient were 5.52±1.36, 5.44±1.11, and 5.09±0.98 respectively. Overall, the bronchus, esophagus and spinal cord maximum doses were similar between VMAT and DWA, but highly reduced compared with CRT. For the lung cases, the mean dose and V20Gy were lower for the arc techniques compares with CRT, while for the liver cases, the mean dose and the V30Gy presented slightly higher values. The average delivery time of VMAT and DWA were 2.46±1.10 min and 4.25±1.67 min, VMAT presenting shorter treatment time in all cases. The DWA dosimetric verification presented an average gamma index passing rate of 95.73±1.54% (range 94.2%-99.8%).

Conclusion:Our preliminary data indicated that the DWA is deliverable with clinically acceptable accuracy and has the potential to further improve the plan quality.

Funding Support, Disclosures, and Conflict of Interest: This collaborative work was supported by the Flemish government through the Hercules foundation and corporate funding from BrainLab AG. The first and the sixth author are financially supported by Brainlab AG. The other authors have no conflict of interest.

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