ESTRO 2023 - Abstract Book

S2042

Digital Posters

ESTRO 2023

Table 1 shows that after a 6D kV-kV match with 5-points masks, 100% of the lateral and longitudinal residual errors are ≤ 0.2 cm. All vertical residual errors were ≤ 0.1cm and all rotational residual errors were ≤ 1°.

The residual errors seen with the 5-points masks are not seen with the frameless masks due to the stability difference of the masks. This indicates a intrafraction movement after performing a roll or pitch and not an inaccurate 6D kV-kV match. Conclusion Small shifts in the CBCT match after a performed kV-kV match are caused by a performed roll or pitch and not by a difference between the kV-kV and CBCT algorithm.

Using 6D kV-kV imaging based on skull structures seems feasible for clinical use. Although it is advised to check for residual errors after a performed pitch/roll with a certain margin.

PO-2271 A predictive model to determine optimal breath-hold parameters in breast radiotherapy

D. Piro 1 , F. Gruosso 1 , M. Aquilano 1 , A. Boschetti 1 , F. Catucci 1 , A. D'Aviero 1 , P. Gaias 1 , M. Iezzi 1 , M. Marras 1 , S. Menna 1 , D. Piccari 1 , E. Pilloni 1 , F. Preziosi 1 , F. Quaranta 1 , A. Re 1 , N. Ulgheri 1 , V. Verusio 2 , C. Votta 1 , V. Valentini 3 , D. Cusumano 1 , G.C. Mattiucci 1 1 Mater Olbia Hospital, Radiotherapy, Olbia (SS), Italy; 2 Università Cattolica del Sacro Cuore, Istituto di Radiologia, Roma, Italy; 3 Fondazione Policlinico Universitario A. Gemelli IRCCS, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Roma, Italy Purpose or Objective The breast radiotherapy treatment is today usually administered in breath hold condition, especially for the left side, to reduce the dose received by the heart. In our Institution a spirometer-based system able to monitor the lungs volume is used to manage the intrafraction motion. During the simulation procedure, a respiratory band is set with a bandwidth arbitrary defined by the radiation therapist (RTT).