ESTRO 2022 - Abstract Book

S1535

Abstract book

ESTRO 2022

An average number of three dummy structures for offline and online dose optimization has been not employed using the ACF approach. Additionally, during the online adaptive process, no more than one dose optimization iteration has been used for the ACF approach. Figure 2 describes the dosimetric comparison for OARs grouped by thorax and abdomen district in terms of minimum, maximum and mean values, as well as for target coverage.

In average, higher OARs sparing and target coverage (especially PTV D50%) have been observed for ACF approach. Also low dose spread region, both in terms of maximum and mean dose, has been reduced by the ACF approach. Conclusion Dosimetric and planning advantages have been observed and quantified when ACF approach has been employed. ACF approach reduces the number of Monitor Units used, so allowing an average reduction of the beam on time. Further analysis will be performed in the next future to better quantify how ACF approach improve not only the plan quality but also reduce the time of the online adaptive MRgRT workflow.

PO-1733 Dosimetric comparison between helical tomotherapy and VMAT for pediatric total lymphoid irradiation

C. Ferrer 1 , C. Huertas 1 , A. Ocanto 2 , D. García 3 , A. Escribano 2 , M. Sáez 1

1 HU La Paz, Medical Physics, Madrid, Spain; 2 HU La Paz, Radiation Oncology, Madrid, Spain; 3 HU La Paz, Medicla Physics, Madrid, Spain Purpose or Objective The aim of this study is to compare the planning of volumetric modulated arc therapy (VMAT) treatments with those planned with helical tomotherapy (HT) in pediatric total lymphoid irradiation (TLI). Materials and Methods TLI treatments are used in the management of pediatric allogeneic hematopoietic stem cell transplantation (HSCT). TLI treatment was prescribed to 8 Gy in 4 fractions, and planned on an Elekta Infinity accelerator with a 160-leaf Agility collimator and VMAT technique with Elekta Monaco TPS (v. 5.11.02). The same treatment was planned on a HD helical