6 MV光子束有无均整器的剂量学特性研究  

Dosimetric characteristics of 6 MV photon beam of linear accelerator with or without flattening filter

作　　者：曾华驱 黄炽雄 钟敏之 ZENG Huaqu;HUANG Chi-xiong;ZHONG Min-zhi(Radiotherapy Center,Gaozhou People’s Hospital,Gaozhou 525200,Guangdong,China;Department of Medical Equipment Office,Shenzhen Hospital,Southern Medical University,Shenzhen 518110,Guangdong,China;Department of Radiology,Guangzhou Red Cross Hospital,Guangzhou 510220,Guangdong,China)

机构地区：[1]高州市人民医院放疗中心,广东高州525200 [2]南方医科大学深圳医院医务部设备处,广东深圳518110 [3]广州市红十字会医院放射科,广东广州510220

出　　处：《生物医学工程与临床》2022年第4期442-449,共8页Biomedical Engineering and Clinical Medicine

摘　　要：目的 研究直线加速器去掉均整器后6 MV光子束的剂量学特性,并与有均整器的情况下比较,为临床应用提供依据。方法 采集瓦里安Trilogy 6 MV光子束在有均整器(FF)(用6X FF表示)和去掉均整器(FFF)(用6X FFF表示)后的剂量学数据,比较两者百分深度剂量(PDD)、离轴剂量分布(Profile)、表面相对剂量(PDD_(1 mm))、射野外相对剂量、总输出因子(S_(cp))。结果 6X FF的最大剂量深度(d_(max))在3 cm×3 cm至15 cm×15 cm射野时为1.4 cm,在20 cm×20 cm射野后变为1.2 cm,30 cm×30 cm后变为1.0 cm,而6X FFF的d_(max)为1.2 cm且不随射野大小变化。在大于d_(max)后,同一深度6X FFF的PDD比6X FF的小,但两者差距随射野和深度变化不明显,在3 cm×3 cm射野5 cm深度处6X FFF的PDD比6X FF的小2.4,在40 cm×40 cm射野30 cm深度处6X FFF的PDD比6X FF的小4.5。6X FFF和6X FF的PDD_(1 mm)在射野3 cm×3 cm,30 cm×30 cm分别为65.65、75.70和55.95、74.80,在大于30 cm×30 cm射野后两者一致。6X FFF的PDD_(1 mm)随射野增大变化没有6X FF显著,且在小于30 cm×30 cm射野时要大于6X FF的PDD_(1 mm)。6X FFF和6X FF的射线质在射野3 cm×3 cm分别为0.510和0.537,随射野增大两者差距增大,在40 cm×40 cm分别为0.594和0.635。6X FF和6X FFF在4 cm×4 cm、10 cm×10 cm、20 cm×20 cm、30 cm×30 cm、40 cm×40 cm射野、10 cm深度几何野外4 cm处的相对剂量分别为1.83、4.48、8.26、10.91、13.31和1.72、4.08、6.34、7.12、7.43,在10 cm×10 cm射野、5 cm、10 cm、20 cm、30 cm深度几何野外4 cm处的相对剂量分别为2.08、4.48、8.51、12.28和2.24、4.08、8.07、11.46。与6X FF相比,6X FFF的离轴剂量分布随深度增加变化不明显,随射野增大,6X FFF呈现尖峰型更加突出;6X FFF的野外剂量下降快,随射野增大,下降量越大。6X FF和6X FFF在3 cm×3 cm、8 cm×8 cm、10 cm×10 cm、20 cm×20 cm、30 cm×30 cm、40 cm×40 cm射野的S_(cp)分别为0.869、0.975、1.000、1.067、1.104、1.126和0.892、0.984、1.Objective To study dosimetric characteristics of 6 MV photon beam in linear accelerator with flattening filter free(FFF),and further compared with the standard flattened beams,for providing basis for clinical application.Method The dosimetric data of Varian Trilogy 6 MV photon beam with FFF(6X FFF)and flattening filter(6X FF)were collected,and percentage depth dose(PDD),off-axis dose distribution(Profile),surface relative dose(PDD1 mm),external-field dose,and total output factor(S_(cp))of them were compared.Results The maximum dose depth(d_(max))of 6X FF was 1.4 cm from 3 cm×3 cm to 15 cm×15 cm fields,1.2 cm in 20 cm×20 cm fields,and 1.0 cm in 30 cm×30 cm fields,while d_(max)of 6X FFF was 1.2 cm and unchanged with various field size.When the depth exceeded d_(max),PDD of 6X FFF was smaller than that of 6X FF at the same depth,but the difference at field and depth was not obvious.The PDD of 6X FFF was 2.4 smaller than that of 6X FF at5 cm depth in 3 cm×3 cm field,the PDD of 6X FFF was 4.5 smaller than that of 6X FF at 30 cm depth in 40 cm×40 cm field.The PDD1 mmof 6X FFF and 6X FF were 65.65,75.70 and 55.95,74.80 in field of 3 cm×3 cm and 30 cm×30 cm,respectively,and which of them were consistent after field larger than 30 cm×30 cm.The PDD1 mmof 6X FFF was not as significant as that of 6X FF in PDD1mmchanged with field enlargement,and was larger than PDD1mmof 6X FF field smaller than 30 cm×30 cm.The ray qualities of 6X FFF and 6X FF were 0.510 and 0.537 in 3 cm×3 cm field,respectively,and the difference increased with increasing of field,which were 0.594 and 0.635 in 40 cm×40 cm field,respectively.The relative doses of 6X FFand 6X FFF at 4 cm×4 cm,10 cm×10 cm,20 cm×20 cm,30 cm×30 cm,40 cm×40 cm field at 10 cm depth and 4 cm from field edge were 1.83,4.48,8.26,10.91,13.31 and 1.72,4.08,6.34,7.12,7.43,respectively,and relative doses at 5 cm,10 cm,20 cm,30 cm depths of 10 cm×10 cm field and 4 cm from field edge were 2.08,4.48,8.51,12.28 and 2.24,4.08,8.07,11.46,respectively.Compared with 6X FF,the P

关 键 词：非均整器 百分深度剂量 离轴剂量分布 总输出因子 

分 类 号：R730.55[医药卫生—肿瘤]