Vassiliev Oleg N, Titt Uwe, Pönisch Falk, Kry Stephen F, Mohan Radhe, Gillin Michael T
The University of Texas M D Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA.
Phys Med Biol. 2006 Apr 7;51(7):1907-17. doi: 10.1088/0031-9155/51/7/019. Epub 2006 Mar 21.
Basic dosimetric properties of 6 MV and 18 MV photon beams from a Varian Clinac 21EX accelerator operating without the flattening filter have been measured. These include dose rate data, depth dose dependencies and lateral profiles in a water phantom, total scatter factors and transmission factors of a multileaf collimator. The data are reviewed and compared with measurements for the flattened beams. The unflattened beams have the following: a higher dose rate by factors of 2.3 (6 MV) and 5.5 (18 MV) on the central axis; lower out-of-field dose due to reduced head scatter and softer spectra; less variation of the total scatter factor with field size; and less variation of the shape of lateral dose profiles with depth. The findings suggest that with a flattening filter free accelerator better radiation treatments can be developed, with shorter delivery times and lower doses to normal tissues and organs.
已测量了Varian Clinac 21EX加速器在不使用均整滤过器情况下产生的6兆伏和18兆伏光子束的基本剂量学特性。这些特性包括剂量率数据、水模体中的深度剂量依赖性和侧向剂量分布、多叶准直器的总散射因子和透射因子。对这些数据进行了审查，并与均整后光束的测量结果进行了比较。未均整光束具有以下特点：中心轴上的剂量率分别提高了2.3倍（6兆伏）和5.5倍（18兆伏）；由于头部散射减少和能谱更软，野外剂量更低；总散射因子随射野大小的变化更小；侧向剂量分布形状随深度的变化更小。研究结果表明，使用无均整滤过器的加速器可以开发出更好的放射治疗方法，治疗时间更短，并减少对正常组织和器官的剂量。
