Toshiro Tsubouchi1, Masashi Yagi2, Iori Sumida1, Keisuke Tamari1, Yuji Seo1, Kazuhiko Ogawa1. 1. Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan. 2. Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan.
Abstract
AIM: To evaluate the influence of the beam shape created by X-rays with "flat beams" and without "flattening-filter-free [FFF] beams" a flattening filter, and the isocenter locations for FFF beams on the treatment of a large irradiated volume for tumours. BACKGROUND: The increase of dose rate and the decrease of out-of-field dose can be expected for FFF beams and lead to effective and safety radiotherapy. On the other hand, the bell-shaped dose profile is thought to be a factor of negating these advantages. MATERIALS AND METHODS: Treatment plans for 15 patients with head and neck cancer were created using XiO (Elekta, Stockholm AB, Sweden) in fixed-gantry step-and-shoot delivery under the same dose constraints. Seven fields of FFF beams with 7 MV and flat beams with 6 MV were used with the technique of intensity-modulated radiation therapy (IMRT). We compared the dose homogeneity and conformity of targets and dose constraints for organs as the plan quality and evaluated physical parameters: monitor unit (MU) values, number of segments and their locations from the isocenter in beam's-eye-view. RESULTS: No significant differences were found in the plan quality. The isocenter locations do not affect the physical parameters for FFF beams. It has been confirmed that the number of segments and MU values were 40% higher with FFF beams than with flat beams (p < 0.05). CONCLUSION: This study demonstrates flat dose distribution is more suitable for IMRT with large and complex targets.
AIM: To evaluate the influence of the beam shape created by X-rays with "flat beams" and without "flattening-filter-free [FFF] beams" a flattening filter, and the isocenter locations for FFF beams on the treatment of a large irradiated volume for tumours. BACKGROUND: The increase of dose rate and the decrease of out-of-field dose can be expected for FFF beams and lead to effective and safety radiotherapy. On the other hand, the bell-shaped dose profile is thought to be a factor of negating these advantages. MATERIALS AND METHODS: Treatment plans for 15 patients with head and neck cancer were created using XiO (Elekta, Stockholm AB, Sweden) in fixed-gantry step-and-shoot delivery under the same dose constraints. Seven fields of FFF beams with 7 MV and flat beams with 6 MV were used with the technique of intensity-modulated radiation therapy (IMRT). We compared the dose homogeneity and conformity of targets and dose constraints for organs as the plan quality and evaluated physical parameters: monitor unit (MU) values, number of segments and their locations from the isocenter in beam's-eye-view. RESULTS: No significant differences were found in the plan quality. The isocenter locations do not affect the physical parameters for FFF beams. It has been confirmed that the number of segments and MU values were 40% higher with FFF beams than with flat beams (p < 0.05). CONCLUSION: This study demonstrates flat dose distribution is more suitable for IMRT with large and complex targets.
Authors: Kees H Spruijt; Max Dahele; Johan P Cuijpers; Marloes Jeulink; Derek Rietveld; Ben J Slotman; Wilko F A R Verbakel Journal: Int J Radiat Oncol Biol Phys Date: 2012-06-05 Impact factor: 7.038
Authors: Daniel R Zwahlen; Stephanie Lang; Jan Hrbacek; Christoph Glanzmann; Stephan Kloeck; Yousef Najafi; Tino Streller; Gabriela Studer; Kathrin Zaugg; Urs M Luetolf Journal: Int J Radiat Oncol Biol Phys Date: 2012-05-07 Impact factor: 7.038
Authors: Yvonne Dzierma; Frank G Nuesken; Jochen Fleckenstein; Patrick Melchior; Norbert P Licht; Christian Rübe Journal: PLoS One Date: 2014-04-10 Impact factor: 3.240