125I粒籽植入术人员受照剂量模拟测量与分析

目的 模拟测量¹²⁵I粒籽植入治疗过程中的工作人员受照剂量,为工作人员的防护提供辐射剂量学数据。方法 根据现场调查中接触粒籽源环节,模拟¹²⁵I粒籽植入手术过程,植入前及植入后,分别测量距离其0.05 m及1 m处的周围剂量当量率水平。植入时,分别将10粒、50粒、100粒、150粒¹²⁵I粒籽源置于治疗床上,分别测量0 mm、1 mm、10 mm、20 mm固体水以及0.25 mmPb的铅方巾覆盖粒籽源的条件下,距离床边10 cm处头部、胸部、腹部的周围剂量当量率水平。头部、胸部、腹部分别代表距地高度155 cm、125 cm和105 cm。手部代表距离辐射源0.05 m。结果 粒籽源活度测定时,井型电离室0.05 m处的周围剂量当量率为0.46～0.64 μSv/h。粒籽源装入植入枪后,其表面的周围剂量当量率为15.7～16.3 μSv/h,所检测的其余各阶段的周围剂量当量率均为本底辐射水平。粒籽植入过程中,随着所植入的粒籽数量的增加,工作人员操作位置的周围剂量当量率水平均随头部、腹部、胸部、手部顺序递增。但随着固体水厚度的增加,各操作位置的周围剂量当量率水平顺序递减。当粒籽源覆盖铅方巾后,其表面的周围剂量当量率均为本底辐射水平。结论 操作¹²⁵I的工作人员所接受的辐射剂量虽未超过相关国家法律法规的要求,但处于较高的水平,需引起足够重视。     

125I粒籽植入放射工作人员受照剂量评估

目的 研究¹²⁵I粒籽植入治疗过程中放射工作人员受照剂量水平,并对其辐射风险进行评估,同时提出合理化的辐射防护建议。方法 本次用于场所防护检测采用100粒单粒活度为0.8 mCi的¹²⁵I粒籽源;单粒¹²⁵I粒籽源周围剂量当量率研究采用的单粒粒籽源出厂活度为0.85 mCi;采用点源模型对不同分工的医务人员受照剂量进行理论计算;同时使用TLD对单粒¹²⁵I粒籽源周围剂量当量率进行测量,使用AT1121型X、γ辐射剂量当量率仪对场所进行布点检测,根据检测结果评估医务人员的受照剂量。结果 术前分装人员,在佩戴0.025 mmPb铅防护手套的情况下手部剂量将降低为5.02 mGy/a;术中手术人员手部剂量将降低为3.01 mGy/a;对于术后护理人员而言,100粒粒籽源在植入深度为2 cm,穿戴0.25 mmPb铅衣的情况下,年受照剂量将降低为0.013 mGy/a。单粒¹²⁵I粒籽源周围剂量当量率测量结果表明距离源30 cm以外基本为本底水平。针对单粒粒子源周围剂量率分布,使用点源模型以及TLD实验测量结果表明,点源模型计算结果较TLD实验测量结果较大,距离越近,相差越大;距离越远两者结果越接近。对于治疗场所而言,使用点源模型以及实验测量结果表明,点源模型较实测结果较大。结论 针对单粒¹²⁵I粒籽源,距离较近时需看作线源,而非点源,因此在距离较近时,点源计算模型较实测结果较大;随着距离的增加,点源计算结果与实测结果越来越接近。建议分装、手术人员、护理病患的护士穿戴防护用品;放射性粒籽植入的患者在手术后穿戴铅围裙或在手术部位覆盖铅防护用品。     

125I粒籽植入治疗辐射防护及关键控制技术探讨

目的 探讨碘-125（¹²⁵I）放射性粒籽植入治疗过程中可能存在的放射性职业病危害因素及辐射水平,探讨关键控制技术。方法 以5家开展¹²⁵I粒籽植入治疗项目的医疗机构为研究对象,采用放射卫生学现场调查、工作场所辐射防护水平检测、人员个人剂量监测等方法,调查粒籽植入涉源工作场所及相关人员的辐射水平;结合源项分析及放射卫生管理经验,根据危害分析与关键控制点（HACCP）的原理,探讨¹²⁵I粒籽植入治疗过程的关键控制点。结果 不同涉源场所中粒籽植入源运输包装、粒籽植入治疗室和专用病房工作场所各关注点的周围剂量当量率为本底~1.80 μSv/h（病房门处）,均小于2.5 μSv/h;35名放射工作人员全年个人剂量监测结果为0.20~1.80 mSv,平均为0.42 mSv。结论 不同涉源场所的辐射水平及人员的受照剂量均符合国家标准限值的要求;应根据关键控制措施,对¹²⁵I放射性粒籽植入治疗过程的关键环节予以控制。     

18F-FDG PET/CT心肌代谢显像受检者的周围辐射剂量水平

目的 探索PET/CT心肌代谢显像受检者周围辐射剂量水平,为保证周围人员辐射安全提供数据支持。方法 选取33例行¹⁸F-FDG PET/CT心肌代谢显像患者,在受检者胸部等高位置按照不同体位方向、时间和距离处对其周围剂量当量率进行测量,探索受检者周围剂量当量率的分布规律。结果 在相同测量时间和距离下,受检者身体两侧的周围剂量当量率相比正、背面更低。受检者注射¹⁸F-FDG显像剂后,距离体表1 m处正面的周围剂量当量率为13～21 μSv/h,检查结束后降至5～14 μSv/h,平均降低46%。受检者周围剂量当量率随距离（10～300 cm）的增加呈幂函数趋势降低,其幂指数均值为−1.2。结论 心肌代谢显像受检者注射药物后周围辐射水平较高,周围剂量当量率随时间和距离增加快速降低,建议心肌代谢显像受检者检查当天避免与他人长时间、近距离接触。     

2013年福建省99台核仪表放射防护检测结果分析

目的 为进一步了解和掌握我省含密封源仪表的放射防护情况。方法 依据国家标准GBZ 125-2009《含密封源仪表的放射卫生防护要求》和GB 18871-2002《电离辐射防护与放射源安全基本标准》对核仪表周围的辐射水平进行检测评价。结果 所检测的99台含密封源仪表离源容器外表面5 cm周围剂量当量率检测结果均值为(10.52±24.08)μSv·h^-1,距源容器外表面1 m周围剂量当量率检测结果均值为(2.12±6.11)μSv·h^-1。检测仪表使用场所要求对人员的活动范围不限制的为28台,占28.3%。结论 所检测的工作场所辐射水平符合国家标准中对源容器使用场所的放射防护要求,说明工作人员安全。     

放射性粒子源植入治疗的防护与安全

目的 讨论放射性粒子源植入治疗的辐射防护与安全。方法 测量放射源周围的剂量分布,对操作人员、患者进行剂量监测。结果 在允许范围内。结论 按操作规程及防护要求来治疗是安全的。     

加速器机房周围剂量当量率理论计算和实际测量结果的对比研究

目的 通过对加速器机房周围剂量当量率理论计算结果与实际测量结果的比较,探讨两者之间的关系及成因。方法 采用十分之一层法估算加速器机房主、次屏蔽墙外的周围剂量当量率,根据国家相关标准推荐的检测方法对加速器机房主、次屏蔽墙外的周围剂量当量率进行检测。结果 各加速器机房周围剂量当量率的实际测量结果均小于理论计算结果,主屏蔽墙周围剂量当量率的测量结果较之理论计算结果偏小30.0%~56.0%。结论 应用十分之一层法来估算加速器机房周围剂量当量率是可行的,偏安全的。     

模拟后装放射源卡源处置时放射工作人员受照剂量研究

目的 估算放疗技师在应急处理后装放射源卡源过程中的受照剂量。方法 使用仿真人体盆腔模型替代宫颈癌患者,填充石蜡的假人替代放疗技师,模拟放射源在患者的子宫口位置发生卡源事故的场景,采用热释光剂量仪测量假人的4个敏感器官（晶体、甲状腺、乳腺、睾丸）表面不同时长内的受照剂量,并计算穿戴0.35 mm铅当量的防护用品的防护效果。结果 按¹⁹²Ir源强370 GBq计,无防护情况下各敏感器官在不同处理时间的受照剂量均小于0.12 mGy。在穿戴防护用品之后,各敏感器官的受照剂量减少1.7%~19.8%。结论 放疗技师在没有穿戴防护用品,¹⁹²Ir源强为370 GBq,应急处理时间35 s内的入射体表剂量不超过0.12 mGy,只相当于做一次X线摄影检查的受照剂量。     

医用电子直线加速器感生放射性的测量和分析

目的 通过对医用电子直线加速器感生放射性进行测量,研究感生放射性冷却规律,并为评估患者、医务人员及公众额外受照剂量提供基础数据。方法 采用automess—6150AD6/H+6150AD-b/H型环境监测X-γ辐射周围剂量当量率仪对5台医用电子直线加速器感生放射性进行测量。结果 5台医用电子直线加速器感生放射性水平与测量位置、时间等因素有关：出束停止后10 s,加速器机头外壳表面5 cm周围剂量当量率最大值为5.55 μSv/h,距外壳1 m处固定点的周围剂量当量率最大值为4.07 μSv/h;在出束停止5 min后,加速器机头外壳表面5 cm周围剂量当量率最大值为2.11 μSv/h,距外壳1 m处固定点的周围剂量当量率最大值为1.77 μSv/h。结论 医用电子直线加速器感生放射性测量结果随时间推移逐渐冷却;测量结果维持在一个较为固定的范围,数值的波动范围较窄。     

我国辐射防护仪器的应用现状和校准

目的 通过分析辐射防护仪器在我国应用现状和存在问题,确立正确使用防护仪的重要性。方法 用在标准剂量学实验室校准的方法,获得不同类型防护仪的校准因子和测量结果的相互关系。结果 对强贯穿辐射外照射进行区域监测,防护仪的测量结果应采用周围剂量当量表达。结论 当测量的光子外照射辐射水平与防护限值接近时,建议将测量值修正到周围剂量当量加以证实。     

Experimental determination of dosimetry parameters for Sinko 125I seed source using a modified polystyrene phantom

Successful treatment for permanent implant brachytherapy is based on accurate measurement of dosimetry parameters for the seed sources. Literature describes the application of various types of phantom to determine the AAPM TG-43 dosimetry parameters for permanent implant seeds. Previously we created a new type of phantom used to measure the dosimetry parameters of a high dose-rate (192)Ir source. In this study, we modified the phantom to suit to a common type of (125)I seed source (Sinko BT-125-1). The dose-rate constant, radial dose function and anisotropy function of this source were measured in detail and compared with the published values of other similar in-design (125)I seed sources. The experimental results exhibit fairly small measurement uncertainties and good self-consistency. The modified phantom is demonstrated on the measurement of dosimetry parameters for the Sinko BT-125-1 (125)I seed, however, it could easily be used for similar measurements of other permanent implantation seed sources.     

采用体模评价DynaCT成像质量和辐射剂量

目的：对C型臂CT（DynaCT）头部扫描成像质量和辐射剂量进行综合分析,并比较多排螺旋CT（MSCT）和DynaCT成像质量和所致患者辐射剂量差异。方法：采用模拟人体体模测量2种成像所致患者的有效剂量,采用CT图像质量控制体模测量2种成像的高对比分辨率和低对比分辨率。DynaCT成像采用自动曝光控制扫描体模,多排螺旋CT采用临床常规扫描条件进行图像采集。结果：DynaCT头部检查有效剂量为1.10mSv,多排螺旋CT头部扫描有效剂量为2.07mSv。2种成像模式头部扫描所致器官剂量存在显著性差异（P〈0.05）。DynaCT和MSCT成像目测高对比分辨率均为12lp/cm;对于DynaCT,当对比度为0.3%时最小可识别物体直径为6mm,而对于MSCT为4mm。结论：对于头部检查DynaCT成像所致患者有效剂量低于MSCT。采用DynaCT成像可以在保证图像质量的同时降低辐射剂量。     

External doses to humans from 137Cs in soil

Calculations of absorbed doses in organs of the human body and the total effective dose due to Cs in soil as a source of external exposure are presented in this work. Calculations were done using the MCNP-4B software package. The assumption was made that photons with an energy of 662 keV are emitted in a cylindrical volumetric source in soil up to the depth of 20 cm. Depth distributions of Cs at 19 locations around Kragujevac (a city in central Serbia) were measured by a HPGe detector. An ORNL phantom of an adult human standing on the soil above the center of a cylindrical radioactive source was used to calculate the conversion coefficients, i.e., absorbed doses in an organ per unit specific activity. The conversion coefficients in organs are given as a function of the source depth in soil. The largest absorbed dose was found in skin. The annual effective dose in humans was estimated from these calculations and the measured activity depth profile of Cs in soil. The average effective dose was found to be 3.17 microSv y. This value was rather small in comparison with other sources of natural ionizing radiation. One may conclude that Cs was a negligible source of external exposure in the area around the city.     

Calculation of midplane dose for total body irradiation from entrance and exit dose MOSFET measurements

This work is the development of a MOSFET based surface in vivo dosimetry system for total body irradiation patients treated with bilateral extended SSD beams using PMMA missing tissue compensators adjacent to the patient. An empirical formula to calculate midplane dose from MOSFET measured entrance and exit doses has been derived. The dependency of surface dose on the air-gap between the spoiler and the surface was investigated by suspending a spoiler above a water phantom, and taking percentage depth dose measurements (PDD). Exit and entrances doses were measured with MOSFETs in conjunction with midplane doses measured with an ion chamber. The entrance and exit doses were combined using an exponential attenuation formula to give an estimate of midplane dose and were compared to the midplane ion chamber measurement for a range of phantom thicknesses. Having a maximum PDD at the surface simplifies the prediction of midplane dose, which is achieved by ensuring that the air gap between the compensator and the surface is less than 10 cm. The comparison of estimated midplane dose and measured midplane dose showed no dependence on phantom thickness and an average correction factor of 0.88 was found. If the missing tissue compensators are kept within 10 cm of the patient then MOSFET measurements of entrance and exit dose can predict the midplane dose for the patient.     

125Ⅰ粒子装载过程中工作人员受照剂量的研究

目的:研究125I粒子装载过程中工作人员受照剂量。方法:选择测量粒子为前列腺癌治疗所用的14.8MBq的125I粒子,测量粒子周围的剂量率,按照平均装载速度及前列腺癌平均的植入粒数86粒,评估125I粒子装载过程中工作人员的受照剂量。结果:在无屏蔽防护情况下,操作人员全身有可能受到高于剂量限值的照射。不同的操作方式,操作人员手部的受照剂量不同,分批倒出粒子装载可以降低手部的受照剂量,分批装载次数越多,手部的受照剂量越低。结论:建议在125I粒子装载中,在L型铅防护屏下或防护通风橱中进行,以降低全身剂量;采用分多次装载的方法,以降低手部的剂量。     

不同水模体直径和不同重建层厚对CT图像噪声的影响

目的 研究不同水模体直径和重建层厚等因素对CT图像噪声的影响，探讨CT质量控制检测中水模体合理的直径范围，为完善我国CT质量控制检测规范提供数据支持。方法 采用GE公司的Revolution型CT机，在两档剂量水平，即CTDI_W分别为30.20 mGy（120 kV、200 mAs）和49.82 mGy（120 kV、330 mAs）、图像重建层厚为5 mm和10 mm的条件下，分别对直径为16、18、20、22、24 cm的圆柱型均质水模体轴向扫描一圈，测量其CT值（水）和噪声等指标。比较不同水模体直径、不同层厚和不同剂量等条件下噪声测量值的差异。结果 噪声测量值随水模体直径增大而增大，随剂量增大而减小，在大小两档剂量水平下水模体直径分别为24、22 cm时的噪声值已超过现有检测标准；噪声随重建层厚的增大而减小。结论 噪声的测量结果与剂量、水模体直径、重建层厚等因素有关，在进行CT质量控制噪声项目的检测时，需规定所选择的剂量水平和层厚大小，并规定所选择水模体的直径大小。本研究结果提示CTDI_W在接近50 mGy的条件下，18~22 cm可能是比较合理的水模体直径范围。     

Extracorporeal irradiation--novel use of a blood product irradiator

A Cs-137 blood product irradiator (BPI) is used for extracorporeal irradiation of bone grafts. For dose verification purposes two bone phantoms were constructed of plaster of Paris and irradiated in the BPI. The first was a hollow cylinder measuring 15 cm x 3.3 cm to simulate cortical bone, filled with paraffin wax to simulate yellow bone marrow. The second was a concave ellipse 11.5 cm x 9.5 cm x 2.5 cm to simulate a section of ilium. The absorbed dose was measured with radiochromic film in the phantoms and in water for comparison with the manufacturer's calibration certificate. The relative dose distribution in the bone phantoms was measured using Li-F thermoluminescent dosimeters and normalized to a reference point near the centre of each phantom. The doses measured in water matched the calibration certificate within 4%. The doses measured at the cylindrical and elliptical phantom reference points were 49.9 Gy and 52.3 Gy respectively, compared to the nominal dose of 50.0 Gy. The relative doses within the cylindrical phantom ranged from 88% to 100% along the central axis of the wax cylinder, from 89% to 100% along the plaster/wax interface, and from 90% to 103% along the outer surface of the plaster cylinder. The relative doses within the elliptical phantom ranged from 100% to 108% along the inside surface, from 99% to 107% along the outer surface, and from 98% to 103% through the centre of the plaster ellipse. These data agree well with the isodose plot provided by the manufacturer.     

Dose distribution from a degraded 60Co gamma field

Dose distribution in two cylindrical phantoms, a small phantom (12.8 cm in diameter and 39.4 cm in length) and a large phantom (25.2 cm and 35.1 cm in length), exposed to a degraded 60Co gamma field was studied. The angular distribution and energy spectrum of the 60Co radiation was changed by ground and air scattering. The dose was measured using thermoluminescent dosimeters (LiF and CaF2). The energy-dependent responses of the dosimeters were corrected using a method developed by Momeni et al. which is based on differential responses of the two types of dosimeters. The dose distribution was calculated from a three-dimensional interpolation-extrapolation of the measured doses. Analysis of the data suggests that the half-value layer concept for a determination of depth dose is not applicable to exposures where the angular distributions and the energy spectra are field variables. Application of thermoluminescent dosimeters for personnel dosimetry in compliance with federal regulations requires correction for the energy dependence of the dosimeters. In exposure cases where the radiation field is nonuniform, use of multiple badges should be considered.