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TY - CONF AU - Bennett, L.C. AU - Vassiliev, O.N. ED - Schaa, Volker RW ED - Power, Maria ED - Shiltsev, Vladimir ED - White, Marion TI - Examination of Out-of-Field Dose and Penumbral Width of Flattening Filter Free Beams in Medical Linear Accelerators J2 - Proc. of NAPAC2016, Chicago, IL, USA, October 9-14, 2016 C1 - Chicago, IL, USA T2 - North American Particle Accelerator Conference T3 - 3 LA - english AB - Medical linear accelerators (LINACS) have traditionally used a flattening filter to ensure that the photon spectrum entering the patient was homogeneous within a given field size. Recently, leading manufacturers of medical accelerators have begun including an option for Flattening Filter Free (FFF) beams on their accelerators. These beams are characterized by a softer spectrum (lower average energy), peaked profiles, and less side scatter. Previous work with Monte Carlo models has shown that the elimination of the flattening filter from the beam path has the potential to greatly reduce scatter in regions immediately adjacent to the primary field (Kry 2010); however, systematic in-depth investigation of these effects has yet to be done using actual measurements from a linac equipped with FFF beams. We have examined and compared measurements of different energy pairings of FFF and FF beams from the Varian TrueBeam accelerators and found reductions of peripheral dose at upwards of 30% for the FFF beams and nearly 5% reduction in penumbral width at nearly all depths and field sizes; reductions were greatest for shallow depths and small field size. PB - JACoW CP - Geneva, Switzerland SP - 396 EP - 398 KW - ion KW - photon KW - linac KW - ECR KW - radiation DA - 2017/01 PY - 2017 SN - 978-3-95450-180-9 DO - 10.18429/JACoW-NAPAC2016-TUPOA54 UR - https://jacow.org/napac2016/papers/tupoa54.pdf ER -