PO-1665: The mesorectum motion using MR-guided Radiotherapy: an exploratory study to quantify PTV margins. (November 2020) - Romano, A.; Chiloiro, G.; Boldrini, L.; Cusumano, D.; Placidi, L.; Antonelli, M.V.; Pollutri, V.; Votta, C.; Gambacorta, M.A.; Valentini, V.