Details

Autor(en) / Beteiligte

• Pang, Pei Ping Eric
• Hendry, Julie
• Cheah, Shie Lee
• Soong, Yoke Lim
• Fong, Kam Weng
• Wee, Tien Seng Joseph
• Tan, Wee Kiat Terence
• Nei, Wen Long
• Wang, Fuqiang
• Wong, Ru Xin
• Ng, Wee Loon
• Chen, John

Titel

An assessment of the magnitude of intra-fraction movement of head-and-neck IMRT cases and its implication on the action-level of the imaging protocol

Ist Teil von

• Radiotherapy and oncology, 2014-09, Vol.112 (3), p.437-441

Ort / Verlag

Ireland: Elsevier Ireland Ltd

Erscheinungsjahr

2014

Quelle

MEDLINE

Beschreibungen/Notizen

• Abstract 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.