Anderson D W, Hwang C C
Health Phys. 1983 Feb;44(2):115-25. doi: 10.1097/00004032-198302000-00002.
Photoneutron dose equivalents and photon doses in the treatment room of a clinical linear accelerator were measured with sets of isotopically enriched LiF thermoluminescent dosimeters and a moderating sphere. Dosimeter neutron calibrations with 252Cf sources were repeated many times during the extended series of measurements because the 6LiF dosimeter sensitivity increased with successive neutron irradiations. Expressed as a fraction of the primary bremsstrahlung beam dose at maximum, the photoneutron background was 2.04 +/- 0.05 mrem/rad (10(-3) Sv/Gy) at 1 m lateral to beam center in the patient midplane at 25 MV. The fraction of this result due to thermal neutrons was found to be only about 2%. The photon background dose was 2.98 +/- 0.04 mrad/rad (10(-3) Gy/Gy). The photoneutron dose equivalent per unit primary dose was found to be nearly independent of the collimator size used but increased by 40% when the bremsstrahlung endpoint energy was increased from 20 to 35 MeV with no change in flattening filters.
利用一组同位素富集的氟化锂热释光剂量计和一个慢化球，测量了临床直线加速器治疗室内的光中子剂量当量和光子剂量。在一系列长时间测量过程中，使用²⁵²Cf源对剂量计进行中子校准的操作重复了多次，因为⁶LiF剂量计的灵敏度会随着连续的中子辐照而增加。在25 MV时，在患者中平面内距束中心横向1 m处，光中子本底以最大初始轫致辐射束剂量的分数表示为2.04±0.05 mrem/rad（10⁻³ Sv/Gy）。发现该结果中由热中子导致的部分仅约为2%。光子本底剂量为2.98±0.04 mrad/rad（10⁻³ Gy/Gy）。发现每单位初始剂量的光中子剂量当量几乎与所使用的准直器尺寸无关，但当轫致辐射端点能量从20 MeV增加到35 MeV且平坦滤波器无变化时，其增加了40%。
