The impact of breathing amplitude on dose homogeneity in intensity modulated proton therapy  Angjelina Protik, Marcel van Herk, Marnix Witte, Jan-Jakob Sonke  Physics and Imaging in Radiation Oncology  Volume 3, Pages 11-16 (July 2017) DOI: 10.1016/j.phro.2017.07.004 Copyright © 2017 The Authors Terms and Conditions

Fig. 1 Schematic overview of the 4D-Motion simulation platform. Each breathing cycle is separated into 10 phases and according to the time stamp the spots are range corrected considering the anatomy of a particular phase and deformed & accumulated back to MidPCT reference anatomy as exemplified by the arrows. Physics and Imaging in Radiation Oncology 2017 3, 11-16DOI: (10.1016/j.phro.2017.07.004) Copyright © 2017 The Authors Terms and Conditions

Fig. 2 Overlay of the relative iso-dose differences between the full TPS total dose recalculation and the WEPL approach on a coronal slice of the patients planning CT scans. Here we present the worst results (3.6% SD over the PTV (big white contour)). The largest deviations appear as small hot and cold spots close to the diaphragm where the pronounced tissue heterogeneities (lung-soft tissue-lung-tumour) were present in each single pencil beam. The legend represents the iso-dose lines expressed as percentage of SD of the dose differences normalized to the reference dose [%].” Physics and Imaging in Radiation Oncology 2017 3, 11-16DOI: (10.1016/j.phro.2017.07.004) Copyright © 2017 The Authors Terms and Conditions

Fig. 3 PTV dose inhomogeneity for single fraction as a function of motion amplitude for the a) combined effects b) interplay effect c) range effect and d) blurring effect for all 10 patients. Results are shown for mid starting phase. Linear quadratic fits are depicted as well. Physics and Imaging in Radiation Oncology 2017 3, 11-16DOI: (10.1016/j.phro.2017.07.004) Copyright © 2017 The Authors Terms and Conditions

Fig. 4 PTV dose inhomogeneity in% (Pat1 123cc, Pat2 140cc and Pat3 606cc) for single fraction introduced by motion effects: interplay (IE), range (RE) and blurring (BE) as a function of motion amplitude for three example patients. Physics and Imaging in Radiation Oncology 2017 3, 11-16DOI: (10.1016/j.phro.2017.07.004) Copyright © 2017 The Authors Terms and Conditions

Fig. 5 Tumour peak-to-peak amplitudes of motion are displayed as a function of PTV size. iso-effect curves represent different percentages (1% up to12%) of PTV dose inhomogeneity due to combined effects that were depicted. Physics and Imaging in Radiation Oncology 2017 3, 11-16DOI: (10.1016/j.phro.2017.07.004) Copyright © 2017 The Authors Terms and Conditions