Mobit P N, Nahum A E, Mayles P
Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, UK.
Phys Med Biol. 1998 Aug;43(8):2015-32. doi: 10.1088/0031-9155/43/8/002.
A Monte Carlo simulation of the quality dependence of different TL materials, in the form of discs 3.61 mm in diameter and 0.9 mm thick, in radiotherapy photon beams relative to 60Co gamma-rays has been performed. The beam qualities ranged from 50 kV to 25 MV x-rays. The TL materials were: CaF2, CaSO4, LiF and Li2B4O7. The effects of the dopants on energy deposition in the TL material have also been determined for the highly sensitive LiF:Mg:Cu:P (TLD-100H) and for CaF2:Mn. It was found that there was a significant difference in the quality dependence factor derived from Monte Carlo simulations between LiF and LiF:Mg:Cu:P but not between CaF2 and CaF2:Mn. The quality dependence factors for Li2B4O7 varied from 0.990 +/- 0.008 (1 sd) for 25 MV x-rays to 0.940 +/- 0.009 (1 sd) for 50 kV x-rays relative to 60Co gamma-rays; Monte Carlo simulations were also performed for Li2B4O7 in megavoltage electron beams. For CaF2, the quality dependence factor varied from 0.927 +/- 0.008 (1 sd) for 25 MV x-rays to 10.561 +/- 0.008 (1 sd) for 50 kV x-rays. The figure for CaSO4 ranged from 0.943 +/- 0.008 (1 sd) for 25 MV x-rays to 9.010 +/- 0.008 (1 sd) for 50 kV x-rays. The quality dependence factor for CaF2 increases by up to 5% with depth and by up to 15% with field size for the kilovoltage x-ray beams. For LiF-TLD, however, there was no significant dependence on the field size or depth of irradiation in the kilovoltage energy range.
针对直径3.61毫米、厚0.9毫米的盘状不同热释光（TL）材料，在放疗光子束中相对于60钴γ射线的质量依赖性进行了蒙特卡罗模拟。束流质量范围为50 kV至25 MV的X射线。TL材料有：CaF2、CaSO4、LiF和Li2B4O7。对于高灵敏度的LiF:Mg:Cu:P（TLD - 100H）和CaF2:Mn，还确定了掺杂剂对TL材料中能量沉积的影响。发现通过蒙特卡罗模拟得出的LiF和LiF:Mg:Cu:P之间的质量依赖性因子存在显著差异，但CaF2和CaF2:Mn之间没有。相对于60钴γ射线，Li2B4O7的质量依赖性因子从25 MV X射线时的0.990±0.008（1标准差）变化到50 kV X射线时的0.940±0.009（1标准差）；还对兆伏级电子束中的Li2B4O7进行了蒙特卡罗模拟。对于CaF2，质量依赖性因子从25 MV X射线时的0.927±0.008（1标准差）变化到50 kV X射线时的10.561±0.008（1标准差）。CaSO4的数值范围从25 MV X射线时的0.943±0.008（1标准差）到50 kV X射线时的9.010±0.008（1标准差）。对于千伏级X射线束，CaF2的质量依赖性因子随深度增加可达5%，随射野大小增加可达15%。然而，对于LiF - TLD，在千伏能量范围内对射野大小或照射深度没有显著依赖性。
