Clinical Research Papers:
Dosimetric superiority of flattening filter free beams for single-fraction stereotactic radiosurgery in single brain metastasis
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Youqun Lai1, Shanyu Chen1, Changdong Xu1, Liwan Shi1, Lirong Fu1, Huiming Ha1, Qin Lin1 and Zhen Zhang1
1 Department of Radiation Oncology, The First Affiliated Hospital of Xiamen University, Xiamen, PR China
Qin Lin, email:
Keywords: flattenig filter free, volumetric modulated arc therapy, stereotactic radiosurgery, brain metastases
Received: July 10, 2016 Accepted: October 28, 2016 Published: November 03, 2016
For single-fraction stereotactic radiosurgery (SRS) using linac in brain metastases, more accurate treatment delivery with higher tumor absorbed doses and lower absorbed doses to normal tissues remains an enormous challenge. The purpose of this study was to investigate the dosimetric superiority in flattening filter free beams (FFF) for volumetric modulated arc therapy (VMAT) in single brain metastasis. 68 patients with single brain metastasis were included in this study. Every patient was subjected to VMAT treatment plans using 6 MV standard flattened (FF) beams (VMAT_FF) and 6 MV FFF beams (VMAT_FFF) with single fraction doses of 20 Gy. Dosimetric evaluation was performed by analysis of target coverage, dose gradients, beam-on time (BOT), gantry speed and number of monitor units (MU). There were no differences between VMAT_FF and VMAT_FFF plans in conformity and MU. VMAT_FFF plans showed obvious superiority in homogeneity, dose gradients and efficiency. For the mean BOT, VMAT_FFF plans provided a significant decrease by 42.8% compared with VMAT_FF. By the use of FFF beams, brain irradiation was minimized with about 2% reductions in low-dose regions (about 5-10 Gy). FFF beams not only resulted in more efficiency by reducing treatment time, but also provided further brain sparing compared to traditional techniques for SRS in single brain metastasis.
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