Mobit Paul, Agyingi Ephraim, Sandison George
Medical Physics Department and Oncology Tom Baker Cancer Centre, 1331-29 Street N W, Calgary, Alberta, Canada T2N 4N2.
Radiat Prot Dosimetry. 2006;119(1-4):497-9. doi: 10.1093/rpd/nci676. Epub 2006 May 30.
A Monte Carlo study of the energy-response factor of aluminium oxide (Al2O3) and lithium fluoride (LiF) TLDs in kilovoltage and megavoltage photon beams relative to 60Co gamma rays has been performed using EGSnrc Monte Carlo simulations. The sensitive volume of the detector was simulated as a disc of diameter 2.85 mm and thickness 1 mm. The phantom material was water and the irradiation depth was 2.0 cm in kilovoltage photon beams and 5.0 cm for megavoltage photon beams. The results show that the energy-response of the Al2O3 and LiF-TLDs is constant within 3% for photon beam energies in the energy range of 60Co gamma rays to 25 MV X rays. However, both detectors show an enhanced response for kilovoltage photon beams, which in the case of 50 kV X rays is 3.2 times higher than that for 60Co gamma rays. The energy-response factor was 1.46 for LiF irradiated in 50 kV X rays. The Al2O3 detector has an energy-response that is 2.2 times higher than that of LiF in 50 kV X rays decreasing to 1.19 for 250 kV X rays. The results show that the addition of 0.1 or 1% of carbon by weight (as dopant) into the Al2O3 does not change the Monte Carlo determined energy-response factor by more than 1%.
利用EGSnrc蒙特卡罗模拟，对千伏和兆伏光子束中氧化铝（Al2O3）和氟化锂（LiF）热释光剂量计相对于60Coγ射线的能量响应因子进行了蒙特卡罗研究。探测器的灵敏体积被模拟为直径2.85毫米、厚度1毫米的圆盘。模体材料为水，在千伏光子束中的照射深度为2.0厘米，在兆伏光子束中的照射深度为5.0厘米。结果表明，对于能量范围在60Coγ射线至25 MV X射线的光子束能量，Al2O3和LiF热释光剂量计的能量响应在3%以内是恒定的。然而，两种探测器对千伏光子束均表现出增强的响应，在50 kV X射线情况下，其响应比60Coγ射线高3.2倍。在50 kV X射线中照射的LiF的能量响应因子为1.46。Al2O3探测器在50 kV X射线中的能量响应比LiF高2.2倍，在250 kV X射线中降至1.19。结果表明，向Al2O3中添加0.1%或1%重量的碳（作为掺杂剂），蒙特卡罗确定的能量响应因子变化不超过1%。
