Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.
Int J Radiat Oncol Biol Phys. 2012 Aug 1;83(5):1655-60. doi: 10.1016/j.ijrobp.2011.10.019. Epub 2012 May 7.
To evaluate the potential usage of flattening filter-free (FFF) photon beams in the treatment of prostate cancer.
Volumetric-modulated arc therapy (VMAT) treatment planning was performed for 7 patients using TrueBeam(®) linear accelerator and photon beams with (X6, X10) and without (X6FFF, X10FFF) flattening filter. Prescribed dose was 19 × 3 Gy = 57 Gy. One or two 360° arcs with dose rate of 600 MU/min for flattened beams, and 1,200 MU/min for FFF beams were used.
No difference was detected between the four beams in PTV coverage, conformity, and homogeneity. Mean body dose and body volume receiving 50% of the prescribed dose decreased with increasing mean energy (r(2) = 0.8275, p < 0.01). X6FFF delivered 3.6% more dose compared with the X6 (p < 0.01). X10FFF delivered 3.0% (p < 0.01), and the X10 5.8% (p < 0.01) less mean body dose compared with X6. There was a significant increase in the mean dose to the rectum for the X10 compared with X6 (2.6%, p < 0.01). Mean dose to the bladder increased by 1.3% for X6FFF and decreased by 2.3% for X10FFF. Using a single arc and FFF, treatment time was reduced by 35% (2 SD = 10%).
FFF beams resulted in dose distributions similar to flattened beams. X10FFF beam provided the best solution, sparing rectum and bladder and minimizing whole-body dose. FFF beams lead to a time efficient treatment delivery, particularly when combined with hypofractionated VMAT.
评估在前列腺癌治疗中使用非均整过滤（FFF）光子束的潜力。
使用 TrueBeam（®）直线加速器和具有（X6、X10）和不具有（X6FFF、X10FFF）均整过滤器的光子束为 7 名患者进行容积调强弧形治疗（VMAT）计划。规定剂量为 19×3 Gy=57 Gy。使用 1 个或 2 个 360°弧，平坦化束的剂量率为 600 MU/min，FFF 束为 1200 MU/min。
在 PTV 覆盖、适形性和均匀性方面，四种光束之间没有差异。随着平均能量的增加（r（2）=0.8275，p<0.01），体剂量和体体积分别减少了 50%。与 X6 相比，X6FFF 多传递了 3.6%的剂量（p<0.01）。X10FFF 传递的剂量少了 3.0%（p<0.01），X10 传递的剂量少了 5.8%（p<0.01）。与 X6 相比，X10 对直肠的平均剂量显著增加（2.6%，p<0.01）。X6FFF 对膀胱的平均剂量增加了 1.3%，X10FFF 则减少了 2.3%。使用单弧和 FFF，治疗时间减少了 35%（2 SD=10%）。
FFF 束产生的剂量分布与平坦化束相似。X10FFF 束提供了最佳的解决方案，能保护直肠和膀胱，使全身剂量最小化。FFF 束可提高治疗效率，尤其是与适形分割 VMAT 相结合时。
