新型双能医用直线加速器非均整剂量学特性研究  

Dosimetric characterization of a novel dual-energy medical linear accelerator without a flattening filter

作　　者：杨鑫[1] 孙文钊[1] 陈利[1] 罗广文[1] 林茂盛[1] 黄晓延[1] 

机构地区：[1]华南肿瘤学国家重点实验室肿瘤医学协同创新中心 中山大学肿瘤防治中心放疗科,广州510060

出　　处：《中华放射肿瘤学杂志》2017年第2期203-209,共7页Chinese Journal of Radiation Oncology

摘　　要：目的利用新型双能医用直线加速器（医科达，Versa HDTM），研究6、10MV能量的FFF和FF光子束剂量学特点，期望找到FFF射束的剂量学特点及优势，为临床应用提供依据。方法比较FFF、FF射束的深度剂量分布，离轴比剂量分布，辐射野大小、半影宽度与野外剂量，准直器散射因子和总散射因子。结果（1）束流能量匹配后的FFF射束与常规均整射束能量一致，各射野百分深度剂量在10cm深度区域的匹配误差〈1％。（2）FFF射束离轴比剂量分布随深度的变化较小。（3）FFF射束的射野大小、半影宽度均比FF射束的变化小，且FFF射束的射野大小、半影宽度，分别随射野和深度的增加逐渐增大；FFF射束各射野的野外剂量比均整射束更低。（4）FFF射束各射野的准直器散射因子和总散射因子，随射野、深度的变化趋势均比FF射束小。结论去除均整器后可明显提高剂量率、减少放疗时间、降低机头的漏射和散射，故FFF除均整性外的剂量学优势．可用于临床SRT。Objective To study the dosimetric characteristics of flattened and flattening filter free （FFF） beams with 6 MV and 10 MV photon energy using a novel dual-energy medical linear accelerator （Elekta Versa HDTM ）, to identify the dosimetrie characteristics and advantages of FFF beams, and to provide a basis for their clinical application. Methods The percentage depth dose （ PDD）, profiles/dose rate of off-axis ratio （OAR）, field size, penumbral width, dose out of the fields, collimator scatter factor （ Sc ）, and total scatter factor （ Sc,p ） were compared between flattened and FFF beams. Results （ 1 ） After beam energy matching, the FFF beams had the same beam energy with the flattened beams. The matching error of PDD at a depth of 10 cm was less than 1% between fields. （2） The FFF beams had a smaller variation in dose rate of OAR with the depth than the flattened beams. （ 3 ） The FFF beams had smaller variations in field size and penumbral width than the flattened beams. Moreover, the penumbral width of the FFF beams increased with the increasing field size or depth. The FFF beams had a lower dose out of the fields than the flattened beams.（4） The FFF beams had smaller variations in Se and S.p with the field size and depth than the flattened beams. Conclusions Removal of the flattening filter can substantially improve the dose rate, shorten radiotherapy time, and reduce leakage and scattering of the head. The dosimetric advantages make the FFF beams appropriate for clinical treatment.

关 键 词：直线加速器 均整器 非均整射束 

分 类 号：R730.55[医药卫生—肿瘤]