Kumar Lalit, Yadav Girigesh, Samuvel Kothanda Raman, Bhushan Manindra, Kumar Pawan, Suhail Mahammood, Pal Manoj
Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India.
Rep Pract Oncol Radiother. 2017 Jan-Feb;22(1):10-18. doi: 10.1016/j.rpor.2016.09.010. Epub 2016 Oct 17.
To investigate the dosimetric influence of filtered and flattening filter free (FFF) photon beam of 6 and 10 MV energies on cervix RA radiotherapy planning and to find possibilities to develop the clinically acceptable RA plans with FFFB photon beam and explore their potential benefits to cervix cancer patients.
FFF photon beams enhances the treatment delivery by increased dose rate which results in shorter treatment time, this shorter treatment time reduces intrafraction motion and enhance comfort to the patients.
RA plans were generated for filtered and flattening filter free photon beams of 6 and 10 MV energies using same dose-volumes constraints. RA plans were generated to deliver a dose of 50.4 Gy in 28 fractions, for a cohort of eleven patients reported with cervix carcinoma. RA plans were evaluated in terms of PTV coverage, dose to OAR's, CI, HI, total no. of monitor units (MUs) and NTID and low dose volume of normal tissues.
Clinically acceptable and similar plans were generated for filtered and flattening filter free photon beams. FFFB delivered slightly higher mean target dose (52.28 Gy vs. 52.0 Gy, = 0.000 for 6 MV and 52.42 Gy vs. 52.0 Gy, = 0.000 for 10 MV) less homogeneous (1.062 vs. 1.052, = 0.000 for 6 MV and 1.066 vs. 1.051, = 0.000 for 10 MV) and less conformal (1.007 vs. 1.004, = 0.104 for 6 MV and 1.012 vs. 1.003, = 0.010 for 10 MV) RA plans compared to FB. FFFB delivered more doses to the bladder and rectum, also required more numbers of MUs in comparison to FB.
This study concludes that FB is more beneficial for cervix RA planning in comparison to FFFB, as FB generates more conformal and homogenous rapid arc plans and offers better OAR's sparing.
研究6兆伏和10兆伏能量的滤过及无均整器（FFF）光子束对宫颈癌容积调强弧形放疗（RA）计划的剂量学影响，寻找制定临床可接受的FFF光子束RA计划的可能性，并探索其对宫颈癌患者的潜在益处。
FFF光子束通过提高剂量率增强了治疗效率，这使得治疗时间缩短，减少了分次治疗期间的运动并提高了患者的舒适度。
使用相同的剂量-体积限制条件，为6兆伏和10兆伏能量的滤过及FFF光子束生成RA计划。针对11例报告患有宫颈癌的患者群体，生成的RA计划为28次分割给予50.4戈瑞的剂量。从计划靶体积（PTV）覆盖度、危及器官（OAR）剂量、适形指数（CI）、均匀性指数（HI）、监测单位总数（MUs）、正常组织积分剂量（NTID）和低剂量体积等方面对RA计划进行评估。
为滤过及FFF光子束生成了临床可接受的相似计划。与滤过光子束（FB）相比，FFF光子束的平均靶区剂量略高（6兆伏时为52.28戈瑞对52.0戈瑞，P = 0.000；10兆伏时为52.42戈瑞对52.0戈瑞，P = 0.000），均匀性较差（6兆伏时为1.062对1.052，P = 0.000；10兆伏时为1.066对1.051，P = 0.000），适形性也较差（6兆伏时为1.007对1.004，P = 0.104；10兆伏时为1.012对1.003，P = 0.010）。与FB相比，FFF光子束给予膀胱和直肠的剂量更多，所需的MUs数量也更多。
本研究得出结论，与FFF光子束相比，FB对宫颈癌RA计划更有益，因为FB能生成更适形和均匀的容积调强弧形计划，并能更好地保护OAR。
