ESTRO 2022 - Abstract Book

S706

Abstract book

ESTRO 2022

Results We found a Δ V gas , Δ d body and Δ d surface of -75.5±113.7ml, -1.1±1.5mm and -2.6±3.3mm, respectively, when pooling all data for analyses. There was a trend of reduction in GI gas and body contour from planning. Separation of body contour and surface correlated moderately to strongly with GI gas (Fig.2). A stronger correlation was found between Δ V gas and Δ d surface (R=0.58) than between Δ V gas and Δ d body (R=0.46). Regarding metrics of surface correction, the strongest correlation with Δ V gas was found for t Y (R=0.58) and r x (R=-0.35), anterior-posterior translation and rotation of the left-right axis, respectively. These findings suggest that anterior surface changes were likely more affected by abdominal distension caused by GI gas, while body contour changes were possibly more affected by other inter-fractional variations such as weight fluctuation and setup errors.

Conclusion Interfractional variation in GI gas volume correlated well with surface variation metrics. Surface imaging may be useful to inform paediatric image guidance protocols and reduce the need for CBCT and associated dose burden, by predicting timepoints with internal changes that warrant additional volumetric imaging. Further work is required to validate our findings using real instead of simulated surface imaging data.

Mini-Oral: 19: Applications of photon & ion beam therapy

MO-0789 Improving Knowledge-based planning for right-side whole-breast tangential field-like delivery

R. Castriconi 1 , L. Marrazzo 2 , S. Calusi 3 , P.G. Esposito 1 , A. Tudda 1 , S. Broggi 1 , P. Mangili 1 , A. del Vecchio 1 , S. Pallotta 2,3 , C. Fiorino 1 1 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 2 Careggi University Hospital, Medical Physics, Florence, Italy; 3 University of Florence, Biomedical, experimental and clinical sciences, Florence, Italy Purpose or Objective To investigate the possibility of training a Knowledge-Based (KB) model by a robust auto-planning technique for the right- sided (R) whole breast treatment with ViTAT (Virtual Tangential Arc Therapy).

Materials and Methods