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Dosimetric Comparison Between Spinal SBRT Treatment Techniques Using IPlan and Elements SRS

C Venencia*, O Apaza , F Munoz , M Almada , Y Schworer , Instituto Zunino, Cordoba, ARGENTINA


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: The purpose of this work was to compare the planning results of a spine SBRT plans using IMRT, HybridArc and VMAT treatment planning technique

Methods: TrueBeam STx (Varian) equipped with HDMLC and 6XFFF beam was used. Treatment volume (55cc) corresponds to an L2 vertebra including the entire vertebral body and the left lateral pedicle. The treatment planning protocol used was 3 fractions of 12Gy and a desired coverage of 90% of the PTV with the prescribed dose, while keeping the OARs doses within tolerances. IMRT plan was done using 15 fix IMRT beams and HybridArc plan using a dynamic arc plus 10 fix IMRT beams; both treatment modalities with iPlan v4.5.5 (Brainlab). The VMAT plan was generated using Elements Spine SRS v1.5 (Brainlab). Plans comparison were done using CI, GI, delivery treatment time, MUs, V50% of the prescribe dose and D95% (D98%) of PTV. Patient specific QA comparison was done using measured absolute dose, independent MU calculation, axial EBT3 film (2%-2mm-Th10%), portal dosimetry and Delta4 (2mm-3%-Th10%) measurement

Results: The CI [GI] for IMRT, HybridArc and Elements plans was 1.53 [5.42], 1.42[5.14] and 1.24 [4.25]. The delivery treatment time and MU needed was 30% less using Elements than IMRT or HybridArc. V50% for IMRT, HybridArc and Elements was 270cc, 240cc and 200cc. D95% [D98%] for IMRT, HybridArc and Elements plans was 28.0Gy [24.0Gy], 30.1Gy [28.1Gy] and 33.8Gy [33.0Gy] respectively. Measured versus calculated dose variation was less than 2% for all plans. Independent MU calculation was 4.1% for IMRT, 1.3% for HybridArc and 1.9% for Element. Gamma passing rate for film and portal dosimetry was better than 99% for all plans. Local gamma using Delta4 was better than 96% for all plans

Conclusion: Elements spine SRS produce better plan quality, require less delivery time and MU than IMRT or HybridArc plans


Not Applicable / None Entered.


TH- External beam- photons: treatment planning/virtual clinical studies

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