清华大学反应堆大动物照射的剂量测定

清华大学游泳池式轻水反应堆1号孔道是国内目前唯一的裂变中子生物辐照场所,通过把不同厚度的铅过滤板横插于入射辐射束中,获得了四种不同中子-γ比释动能比率的混合中子-γ辐射条件,对狗进厅单侧照射。狗体模由TE液体组成,用双电离室方法测量吸收剂量.上述四种混合辐射场的中子-γ比值分别为l 0.6,2.06、1.12和0.16。确定了不同中子-γ比条件下沿水平中心线的深度剂量分布.给出了中心剂量、入射剂量和出射剂量值。按照lCRU10_e报告建议的划分照射均匀程度的指标,四种条件下的大动物(狗)照射都属于非均匀照射.     

细胞遗传学技术在辐射事故生物剂量估算的研究进展

对现有几种生物剂量测定方法如：染色体畸变、微核、早熟染色体凝集及新近开展的荧光原位杂交、ＨＰＲＴ、ＧＰＡ等在辐射事故剂量估算中的应用情况作了介绍。     

快中子（35MeV_（p→Be））单次照射后小鼠骨髓的近期相对生物学效应研究

快中子（３５ＭｅＶ_（ｐ→Ｂｅ））单次照射后小鼠骨髓的近期相对生物学效应研究孙艳，韩树奎，徐博，张淑惠，唐景华，常维克，申文江快中子治癌与光子相比具有一定的优越性，特别是对于那些亚致死性和潜在致死性损伤修复能力强的、再氧合能力差的和乏氧细胞比例高的肿?..     

肿瘤细胞对p(35)Be快中子的辐射敏感性研究

目的 比较肿瘤细胞p(35)Be块中子及γ射线的辐射敏感性,为肿瘤的快中子治疗提供理论依据。方法 用细胞集落在存活方法研究人黑色素瘤细胞（WM9839）、人口 皮癌细胞（KB）、人结肠腺癌细胞（LS－T－117）和人前列腺癌细胞（PC3M）等4种细胞对快中子及γ射线的辐射敏感性,用彗星电泳技术研究WM9839细胞在快中子及γ射线照射后DNA损伤的修复效应。结果 细胞存活实验表明,p(35)Be快中子照射后4种肿瘤细胞的D0值（或SF2值）较γ射线照射后差异减小,即4种肿瘤细胞对快中子的辐射敏感性差异减小;快中子2Gy照射后,WM9839细胞DNA损伤修复曲线整体上下降较γ射线2Gy照射后慢,到180min时,DNA损伤残留率明显高于γ射线2Gy照射。结论 快中子治疗肿瘤可以很好地弥补低LET射线放射治疗的不足,特别是对低LET射线较为耐受的肿瘤细胞,如KB细胞和WM98309细胞。     

国内放射生物学研究中物理剂量报告规范性现状调查

目的 通过文献调查,了解国内放射生物学研究中物理剂量参数的规范性现状。方法 调查国内两本重要的学术期刊——《中华放射肿瘤学杂志》和《中华放射医学与防护杂志》近5年发表的放射生物学论文,针对物理剂量学参数,按照美国国家癌症研究所(NCI)和Desrosiers等推荐的评分系统对其书写的规范性进行评分(满分10分)。结果 两本杂志共纳入222篇文献,中位得分为5.0分。其中,有72.1%的文献得分为4.0~7.0分,有68.0%的文献得分≤5.5分,另有18.5%得分≤3.0分。有90.1%和97.7%的文献分别描述了"射线类型"、"吸收剂量",平均得分最高(0.90和0.98分),"剂量学校准"平均得分最低(0分)。结论 尽管绝大多数文献都描述了"射线类型"和"吸收剂量",但大多数其他细节未被报告。这表明在国内放射生物学研究中物理剂量学报告的规范性存在缺陷,预计可能影响研究结果的可再现性和可解释性,应被重视。     

硼中子俘获治疗的辐射场特点与剂量估算

BNCT（硼中子俘获治疗）基于这样一种思想：^10B的载体化合物会优先选择癌细胞作为靶而后与热中子反应，进而产生高能、短射程裂变产物α粒子和Li粒子。它是一种双重的靶向治疗方法。BNCT的治疗效果依赖于两个主要因素：源于^10B（n,α）^7Li核反应的高LET（传能线密度）粒子的生物效应和在靶细胞及其特异区域内的硼沉积。本总结和探讨了BNCT的发展概况、辐射场的特点以及吸收剂量的计算方法。     

硼中子俘获治疗的辐射场特点与剂量估算

BNCT(硼中子俘获治疗)基于这样一种思想:10B的载体化合物会优先选择癌细胞作为靶而后与热中子反应,进而产生高能、短射程裂变产物α粒子和Li粒子。它是一种双重的靶向治疗方法。BNCT的治疗效果依赖于两个主要因素:源于10B(n,α)7Li核反应的高LET(传能线密度)粒子的生物效应和在靶细胞及其特异区域内的硼沉积。本文总结和探讨了BNCT的发展概况、辐射场的特点以及吸收剂量的计算方法。     

染色体畸变分析作为生物剂量估计的研究进展

介绍染色体畸变分析作为放射生物剂量测定方法在事故中的应用概况，重点介绍对当前分子细胞遗传学方法主要是ＦＩＳＨ技术在生物剂量学中的研究。     

细胞遗传学技术在辐射事故生物剂量估算的研究进展

对现有几种生物剂量测定方法如:染色体畸变、微核、早熟染色体凝集及新近开展的荧光原位杂交、HPRT、GPA等在辐射事故剂量估算中的应用情况作了介绍。迄今,染色体畸变仍是各种生物剂量测定方法中研究最多、较为可靠的一种。分子细胞遗传学方法,主要是FISH的建立和应用,对解决慢性长期照射和早先照射的剂量估算将是一种具有实用前景的方法。     

放射生物剂量学研究的新进展

放射生物剂量学方法在历次放射事故应急处置中起到非常重要的作用,主要采用非稳定性染色体畸变和微核分析。最近的研究关注快速高通量的生物剂量计的探索,不仅涉及上述方法的自动化,还涉及DNA双链断裂、基因表达等分子生物学剂量计的研究以及代谢组学和血清学指标的筛选。笔者主要就2012-2014年放射生物剂量学研究的新进展进行综述。     

Revisiting the 7Li(p,n)7Be reaction near threshold

In this work we review all the available experimental neutron data for the ⁷Li(p,n) reaction near threshold which is necessary to obtain an accurate source model for Monte Carlo simulations in Boron Neutron Capture Therapy. Scattered published experimental results such as cross sections, differential neutron yields and total yields were collected and analyzed, exploring the sensitivity of the fitting parameters to the different possible variables and deriving a consistent working set of parameters to evaluate the neutron source near threshold.     

~(125)Ⅰ植入治疗源的剂量学参数的Monte Carlo模拟

放射性粒子源125I已被广泛用于前列腺和眼睛的植入治疗中。本文采用EGS5蒙特卡罗代码计算了美国医用物理学协会（AAPM）TG-43U1报告中推荐的型号为6711125I近距治疗源（活性区长取0.28cm）的剂量学参数,如剂量率常数、径向剂量函数和各向异性函数。剂量率常数为0.959cGy/h/U,与TG-43U1推荐值和Dolan等已发表的值相差在2.0%以内 径向剂量函数数值与二者均符合较好 随着角度和距离的增加,各向异性函数值数值与二者的复合程度趋佳。并给出了实用性较强的径向剂量函数的拟合公式。     

Semi-empirical systematics of (n, p) reaction cross sections for 14.5 MeV neutrons

A new semi-empirical formula for the calculation of the (n, p) cross section at 14.5 MeV neutron energy is obtained. Derived from the evaporation statistical model, the new formula includes five parameters and shows for the first time a strong dependence of the (n, p) cross section on terms of the parameter (2Z−1)/A. Fitting this formula to the existing cross section data on 161 nuclei with 40≤A≤209, the adjustable parameters have been determined and the systematics of the (n, p) reaction have been studied. The predictions of this formula are compared with those of the existing formulae and with the experimental data. The formula with five parameters is found to give a better fit to the data than the previous comparable formulae.     

Near-threshold 7Li(p,n)7Be neutrons on the practical conditions using thick Li-target and Gaussian proton energies for BNCT

The near threshold ⁷Li(p,n)⁷Be neutrons generated by incident proton energy having Gaussian distribution with mean energies from 1.85 to 1.95 MeV, were studied as a practical neutron source for BNCT wherein an RFQ accelerator and a thick Li-target are used. Gaussian energy distributions with the standard deviation of 0, 10, 20 and 40 keV for mean proton energies from 1.85 to 1.95 MeV were surveyed in 0.01 MeV increments. A thick liquid Li-target whose dimensions were established in our previous experiments (i.e., 1 mm-thick with 50 mm width and 50 mm length) was considered in this study. The suitable incident proton energy and physical dimensions of Pb layer which serves as a gamma absorber and a Polyethylene layer which is used as a BDE were surveyed by means of the concepts of TPD. Dose distribution were calculated by using MCNP5. A proton beam with mean energy of 1.92 MeV and a Gaussian energy distribution with a standard deviation of 20 keV at a current of 10 mA was selected from the viewpoint of irradiation time and practically achievable proton current. The suitable thicknesses of Pb gamma absorber was estimated to be about 3 cm. The estimated thickness of the polyethylene BDE was about 24 mm for an ideal proton current of 13 mA, and was 18 mm for a practical proton current of 10 mA.     

Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC)

Objectives:

To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography.

Methods:

Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO^® head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC).

Results:

The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4.

Conclusions:

The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.     

Optimization parameters for BDE in BNCT using near threshold 7Li(p,n)7Be direct neutrons.

The dose contribution of (10)B(n,alpha)(7)Li reaction in BNCT using near threshold (7)Li(p,n)(7)Be direct neutrons can be increased through the use of materials referred to as boron-dose enhancers (BDE). In this paper, possible BDE optimization criteria were determined from the characteristics of candidate BDE materials namely (C(2)H(4))(n), (C(2)H(3)F)(n), (C(2)H(2)F(2))(n), (C(2)HF(3))(n), (C(2)D(4))(n), (C(2)F(4))(n), beryllium metal, graphite, D(2)O and (7)LiF. The treatable protocol depth (TPD) was used as the assessment index for evaluating the effect of these materials on the dose distribution in a medium undergoing BNCT using near threshold (7)Li(p,n)(7)Be direct neutrons. The maximum TPD (TPD(max)) did not exhibit an explicit dependence on material type as evidenced by its small range and arbitrary variations. The dependence of TPD on BDE thickness was influenced by the BDE material used as indicated by the sharply peaked TPD versus BDE thickness curves for materials with hydrogen compared to the broader curves obtained for those without hydrogen. The BDE thickness required to achieve TPD(max) (BDE(TPD(max))) were also found to be thinner for materials with hydrogen. The TPD(max), the dependence of TPD on BDE thickness, and the BDE(TPD(max)) were established as appropriate BDE optimization parameters. Based on these criteria and other practical considerations, the suitable choice as BDE among the candidate materials considered in this study for treatments involving tumors located at shallow depths would be (C(2)H(4))(n) while beryllium metal was judged as more appropriate for treatment of deep-seated tumors.     

核查放射治疗非参考条件下光子和电子线束剂量学参数方法研究

目的 研究用热释光剂量计（TLD）核查非参考条件下光子线束和电子线束剂量学参数方法。方法 用⁶⁰Co γ线束,高能X射线束和电子线束,开展TLD分散性、非线性剂量响应、衰退、能量和有机玻璃支架（IAEA提供）等校正实验,建立估算TLD水中光子线束和电子线束吸收剂量方法。选择了⁶⁰Co,6、10、15和18 MV光子线束（离轴）,剂量随着照射野和30°楔形角度变化研究;选择了6和10 MV光子线,剂量随着源皮距,照射野和楔形角度变化进行可靠性研究;选择了9和15 MeV电子线,剂量随着源皮距离变化进行可靠性研究。结果 用建立的TLD方法,估算非参考条件下光子线束（离轴）研究结果,相对偏差在-0.1%~7.2%（IAEA要求不大于±7.0%）范围内。非参考条件光子线束（轴上）验证研究结果,相对偏差在0.1%~7.0%范围内;参考和非参考条件电子线束验证研究结果,相对偏差为0~4.7%（IAEA要求不大于±5.0%）范围内。结论 用TLD核查放射治疗非参考条件临床的剂量学参数方便准确,经在医院做可靠性验证,对高能电子线束,用平行板电离室校准吸收剂量,用TLD验证,效果很好。     

Experimental verification of beam characteristics for cyclotron-based epithermal neutron source (C-BENS)

A cyclotron-based epithermal neutron source has been developed for boron neutron capture therapy. This system consists of a cyclotron accelerator producing 1.1-mA proton beams with an energy of 30 MeV, a beam transport system coupled with a beryllium neutron production target, and a beam-shaping assembly (BSA) with a neutron collimator. In our previous work, the BSA was optimized to obtain sufficient epithermal neutron fluxes of using a Monte Carlo simulation code. In order to validate the simulation results, irradiation tests using multi-foil activation at the surface of a gamma-ray shield located behind the collimator and water phantom experiments using a collimated epithermal neutron beam were performed. It was confirmed experimentally that the intensity of the epithermal neutrons was 1.2×10⁹ cm⁻² s⁻¹.