Hospital Universitario Puerta de Hierro Majadahonda, Madrid, Spain.
Radiother Oncol. 2012 Jan;102(1):135-41. doi: 10.1016/j.radonc.2011.06.012. Epub 2011 Jul 5.
Small radiation beams (<4 cm width) are being increasingly used in the delivery of advanced techniques as Intensity Modulated Radiotherapy (IMRT) and Stereotactic Radiosurgery (SRS). Dose measurements in small beams present challenges not encountered for larger beams. A postal audit with Thermoluminiscent Dosimeters (TLD) was developed to check the doses in small photon beams. A validation test in real conditions was carried out in fourteen centres.
The TLD postal audit employs very small chips (1×1×1 mm(3)) of TLD-100 inserted at 5 and 10 cm of depth in a cylindrical PMMA phantom designed for this purpose. This experimental system is mailed to the audited centres to be irradiated with beams of 1 and 3 cm of side or diameter. The prescribeddose is 1.5 Gy at 10 cm. The properties of this system were studied experimentally and by Monte Carlo (MC) simulation, before the external test.
Deviations between the prescribed and measured absorbed doses are below 5% for 69% (1×1 cm(2) beam) and 64% (3×3 cm(2) beam) of the audited centres. When deviations are above 5%, their causes have been investigated and led to corrections.
The developed postal audit is suitable to verify the absorbed doses in small photon beams with an accuracy of 2.9% (1 s).
小射线束（<4cm 宽）越来越多地应用于先进技术的传递，如强度调制放射疗法（IMRT）和立体定向放射外科（SRS）。在小射束中进行剂量测量会遇到与大射束不同的挑战。本文开发了一种使用热释光剂量计（TLD）的邮寄审核方法，以检查小光子射束中的剂量。在 14 个中心进行了真实条件下的验证测试。
TLD 邮寄审核采用非常小的 TLD-100 芯片（1×1×1mm³），插入为此目的设计的圆柱形 PMMA 体模中 5cm 和 10cm 深处。将该实验系统邮寄到审核中心，用 1cm 和 3cm 边长或直径的射束照射。规定剂量为 10cm 处的 1.5Gy。在外部测试之前，通过实验和蒙特卡罗（MC）模拟研究了该系统的特性。
对于 69%（1×1cm² 射束）和 64%（3×3cm² 射束）的审核中心，规定剂量和测量吸收剂量之间的偏差低于 5%。当偏差超过 5%时，已经调查了其原因，并进行了校正。
开发的邮寄审核适用于验证小光子射束中的吸收剂量，精度为 2.9%（1s）。
