BACKGROUND AND PURPOSE: A planning margin ⩽3 mm is employed in some head-and-neck IMRT cases due to the proximity of critical structures. This study aims to explore the need to redefine the action-level in the head-and-neck imaging protocol in consideration of the intra-fraction movement. MATERIAL AND METHODS: This is a local study of 18 patients treated using the same immobilisation system and setup protocol. Post-treatment orthogonal pair of kilovoltage X-ray images was acquired on the first three days of treatment. 106 sets of pre- and post-treatment kV X-ray images acquired over 53 fractions were analysed against the treatment planning DRR for calculation of intra-fraction movement. RESULTS: Individual mean intra-fraction movement in all directions ranged from -1.8 to 1.1 mm. Population mean (median) intra-fraction movement in the x-, y-, and z-planes were -0.1 mm (0 mm), -0.3 mm (-0.3 mm) and -0.2 mm (-0.2 mm) respectively. Intra-fraction movement in all three dimensions, x-, y- and z-planes were considered statistically significant (p<0.05). 7 out of 53 fractions (13.2%) were highlighted as the combined magnitude of the intra-fraction motion with the uncorrected pre-treatment setup errors had exceeded the boundaries of given margins. CONCLUSIONS: 3 mm-AL was not adequate to account for intra-fraction movement when the CTV-PTV margin was ⩽3 mm and should be excluded from the routine imaging protocol and daily image-guided radiotherapy should be employed. Adjusting the action-level to 2 mm would allow a more confident approach in delivery of the prescribed dose in head-and-neck IMRT cases.
BACKGROUND AND PURPOSE: A planning margin ⩽3 mm is employed in some head-and-neck IMRT cases due to the proximity of critical structures. This study aims to explore the need to redefine the action-level in the head-and-neck imaging protocol in consideration of the intra-fraction movement. MATERIAL AND METHODS: This is a local study of 18 patients treated using the same immobilisation system and setup protocol. Post-treatment orthogonal pair of kilovoltage X-ray images was acquired on the first three days of treatment. 106 sets of pre- and post-treatment kV X-ray images acquired over 53 fractions were analysed against the treatment planning DRR for calculation of intra-fraction movement. RESULTS: Individual mean intra-fraction movement in all directions ranged from -1.8 to 1.1 mm. Population mean (median) intra-fraction movement in the x-, y-, and z-planes were -0.1 mm (0 mm), -0.3 mm (-0.3 mm) and -0.2 mm (-0.2 mm) respectively. Intra-fraction movement in all three dimensions, x-, y- and z-planes were considered statistically significant (p<0.05). 7 out of 53 fractions (13.2%) were highlighted as the combined magnitude of the intra-fraction motion with the uncorrected pre-treatment setup errors had exceeded the boundaries of given margins. CONCLUSIONS: 3 mm-AL was not adequate to account for intra-fraction movement when the CTV-PTV margin was ⩽3 mm and should be excluded from the routine imaging protocol and daily image-guided radiotherapy should be employed. Adjusting the action-level to 2 mm would allow a more confident approach in delivery of the prescribed dose in head-and-neck IMRT cases.
Authors: Oliver J Gurney-Champion; Dualta McQuaid; Alex Dunlop; Kee H Wong; Liam C Welsh; Angela M Riddell; Dow-Mu Koh; Uwe Oelfke; Martin O Leach; Christopher M Nutting; Shreerang A Bhide; Kevin J Harrington; Rafal Panek; Kate L Newbold Journal: Int J Radiat Oncol Biol Phys Date: 2017-10-16 Impact factor: 7.038
Authors: Matthias Felix Haefner; Frederik Lars Giesel; Matthias Mattke; Daniel Rath; Moritz Wade; Jacob Kuypers; Alan Preuss; Hans-Ulrich Kauczor; Jens-Peter Schenk; Juergen Debus; Florian Sterzing; Roland Unterhinninghofen Journal: Oncotarget Date: 2018-01-08
Authors: André Haraldsson; Sofie Ceberg; Crister Ceberg; Sven Bäck; Silke Engelholm; Per E Engström Journal: J Appl Clin Med Phys Date: 2020-06-26 Impact factor: 2.102