Room: ePoster Forums
Purpose: Implementation of DIBH technique using RapidArc in Truebeam STx for its clinical use in left sided breast cancer
Methods: A Truebeam STx equipped with real time position management system (RPM, Varian) was used. The breathing signal was obtained by the optical camera, tracking the movement of the reflector block. A respiratory phantom (Brainlab) with three movement modalities: static position, free breathing (amplitude 1.6cm, sinusoidal wave and breathing period of 5 seconds) and DIBH (gated limits 20% of maximum amplitude, breath hold 10 seconds) was used. A Rapidarc plan with a recognizable form with angles and borders (letter S) was planned on Eclipse TPS. Phantom positioning was achieved using gated MV-KV orthogonal images, using markers fusion and 2D-3D comparison. Static versus gated DIBH CBCT was compared using distances between phantom internal markers. The accuracy of the dose delivery was verified comparing static, free breathing (FB) and gated treatments using EBT3 film dosimetry on a coronal plane (Î³<1, 3%-2mm-Th30%) and absolute dose variation using ion chamber measurement.
Results: Plan delivery time without interruption was 2:51min and its increased 50% (30%) with 10s (20s) breath hold. The differences between static and DIBH CBCT was less than 0.1cm. The difference between phantom positioning using gated orthogonal MV-KV and DIBH CBCT was less than 0.1cm. Dose distribution comparison between static and FB plans showed less than 60% of the pixels with Î³<1 and absolute dose variation higher than 40%. Dose distribution comparison between static and gated DIBH plans showed 99.8% of the pixels with Î³<1 and absolute dose variation less than 1%
Conclusion: Truebeam STx equipped with RPM system is capable to delivery gated DIBH Rapidarc plans for left sided breast cancer. Gated DIBH CBCT and MV-kV images can be used for patient positioning.
Not Applicable / None Entered.