ESTRO 2023 - Abstract Book

S1789

Digital Posters

ESTRO 2023

A. Bresolin 1 , F. La Fauci 1 , G. Reggiori 1,2 , N. Lambri 1,2 , M. Pelizzoli 1 , S. Parabicoli 1 , P. Gallo 1 , L. Paganini 1 , F. Lobefalo 1 , S. Tomatis 1 , M. Scorsetti 1,2 , P. Mancosu 1 1 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery Department, Milan, Italy; 2 Humanitas University, Department of Biomedical Sciences, Milan, Italy Purpose or Objective AcurosXB (AXB) is a type C algorithm for the delivered dose estimation. AXB for lung VMAT plan optimization could induce higher fluency in the low density inside PTV in comparison to type A/B algorithms. The goals of the current work are: (1) to highlight the role of AXB during the inverse optimization of lung plans (2) to investigate the likely scenario tracking the GTV amongst the 4DCT phases (3) to show the difference between a homogeneous and inhomogeneous dose prescription case. Materials and Methods Modulated plans for lung hypo-fractionated radiotherapy (48-50Gy in 4-5 fractions) were considered. The free-breathing CT (FBCT) was used for dose optimization and reporting. In all cases, the final dose calculation was performed with AXB. Two optimizations were considered: w/ and w/o intermediate dose with AXB, i.e., Pencil Beam (PB) + AXB algorithms vs. PB alone. Each optimization was performed for both homogeneous (i.e., PTV_V100%=50% with PTV_V95%>95% and PTV_V105%<5%) and inhomogeneous (i.e., PTV_V98%=99% with Internal Target Volume ITV_V120%=99% and 135%-500HU.