CT检查患者的非病变部位防护研究

目的 探讨患者在实施CT检查时,非检查部位特别是敏感器官在防护前、后X射线受照剂量的变化;讨论非检查部位防护的价值及意义。方法 在患者接受CT检查时,随机抽取40位患者,征得同意后将剂量计分别置于非检查区敏感器官的皮肤表面,在一次检查中,测得不同敏感器官表面受照剂量;另选择40位患者,征得同意后,用1.5 mmPb的铅橡皮对非检查部位进行防护,然后测量敏感器官对应皮肤表面受照剂量。结果 防护前非检查部位敏感器官对应皮肤表面接受的射线剂量明显高于防护后敏感器官对应皮肤表面接受的射线剂量(P < 0.001)。结论 患者非检查部位的X射线防护能明显降低患者的辐射剂量,对减少患者辐射损伤具有重要价值。     

患者CT检查非检查部位放射防护的价值和意义

目的 探讨患者在医疗CT检查时,非检查区域特别是敏感器官在防护前、后接受X射线剂量的变化;讨论非检查区域防护的价值及意义。方法 在患者接受CT检查时,随机将抽取40位患者,征得同意后将射线剂量计分别置于非检查区的敏感器官的皮肤表面,在一次检查中,测得不同敏感器官表现的接受剂量;另选择40位患者,征得同意后,用1.5个铅当量的铅橡皮对非检查区域进行防护,然后测量敏感器官对应皮肤表面受照剂量。结果 防护前非检查部位的敏感器官对应皮肤表面接受的射线剂量明显高于防护后敏感器官对应皮肤表面接收的射线剂量(P<0.001)。结论 患者非检查部位的X射线防护能明显降低患者的辐射剂量,对减少患者辐射损伤具有重要价值。     

仿真儿童体模头部CT检查剂量及屏蔽防护效果研究

目的 本研究通过利用仿真儿童人体模型实验来研究儿童头颅CT扫描的各器官和组织的吸收剂量和有效剂量，探讨采取屏蔽防护措施降低剂量的效果。方法 使用GE HD750型CT进行儿童头颅CT扫描，在1岁、10岁两种儿童仿真体模内布放热释光剂量计，获得在非投照部位未防护及采用0.5 mmPb的铅橡胶方巾包裹屏蔽两种条件下儿童组织和器官的吸收剂量，并计算有效剂量，讨论采取铅橡胶方巾包裹屏蔽在儿童头颅CT检查中对辐射的屏蔽效果。结果 1岁儿童体模实验防护组较未防护组的甲状腺、肺、胃、肠和乳腺等敏感组织器官的吸收剂量降低40.4%以上，有效剂量由4.9 mSv降低至2.2 mSv，降低了55.7%；10岁儿童体模敏感器官的吸收剂量降低了39.5%以上，有效剂量由2.4 mSv降低至1.7 mSv，降低了30.5%。结论 采用铅橡胶方巾包裹防护可以明显降低各器官或组织的吸收剂量和有效剂量。     

某医院消化内科介入防护装置效果评价

目的 比较消化内科在使用铅防护屏、床侧防护吊帘和房顶防护吊帘的综合防护措施前后工作人员操作位辐射场分布特征。方法 对介入治疗时操作立位防护平面的13个测试点在防护前后分别进行辐射剂量水平监测。结果 介入治疗人员所接受的辐射剂量未加防护前为(382±113)μSv·h^-1;防护后为(49.7±32.2)μSv·h^-1。结论 射线是可防的,特别是操作时球管在下、不动或基本不动(如消化内科、骨科、碎石机等),采取综合防护措施,能有效降低工作人员受照剂量。     

大中专入校新生X射线胸透检查致工作人员辐射剂量的调查

目的 了解大中专入校新生X射线胸透检查致工作人员所受辐射剂量。方法 运用热释光方法调查25位从事大中专学生入学X射线胸透检查工作人员受照剂量。结果 一个年度入校新生X射线透视检查放射工作人员头部、胸部、背部、左右手部位所受剂量在4.44~5.04mSv之间,最高为头部5.04mSv,右手次之为4.98mSv,最低为左手4.44mSv,高于目前我国放射工作人员的平均年剂量当量水平。结论 建议取消大中专学生在高考前、入校后及毕业前进行X射线胸透普查,可考虑对重点人群进行X射线胸透检查或以拍片代替胸透检查,以降低受检者剂量。     

移动CT与普通CT扫描致受检者敏感器官剂量及辐射场分布比较

目的 通过测量移动CT与普通CT扫描所致受检者敏感器官(眼晶体、甲状腺、胸腺、乳腺、小肠、性腺)体表皮肤入射处空气比释动能及辐射场分布情况,了解移动CT和普通CT扫描各自剂量特点,为合理应用及采取防护措施提供科学依据。方法 用热释光剂量计(TLD)测量CT受检者六个敏感器官体表剂量和周围环境剂量。结果 移动CT扫描致受检者剂量具有新特点,头部扫描眼晶体体表剂量平均为66.6mGy,转换为脑部吸收剂量约为61.62mGy,是普通CT的2.8倍,也高于头部CT扫描的医疗照射指导水平50mGy;邻近投照部位的甲状腺和胸腺处剂量高于普通CT,而乳腺、小肠、性腺和周围环境的剂量低于普通CT。加防护后,相应部位的剂量明显降低。结论 应按照移动CT的特性及功能,合理应用,并注重受检者非投照部位的防护。     

PET/CT放射性核素的分装和注射人员受照剂量

目的 测量PET/CT中心分装和注射人员职业受照剂量,为PET/CT中心防护设计和国家防护标准制定提供基本资料。方法 应用普通TLD测量PET/CT中心分装和注射人员胸部、颈部受照剂量,用指环剂量计测量他们手部剂量,每月测量一次,共测量6个月;同时在铅衣内、外相对位置粘贴剂量计,比较两者剂量大小。结果 PET/CT中心分装和注射人员全身剂量较高,他们分担了各自中心集体剂量的64%~94%;甲状腺受照剂量为1.20~1.70mSv/a,个别人员手部剂量超过了500mSv/a;穿铅衣可以将受照剂量减少8%。结论 分装和注射人员是PET/CT中心主要的受照人群,需要采取更多的措施降低他们的受照剂量,尤其是手部剂量。     

儿童CT扫描体表剂量水平与分析

目的 测量分析儿童CT扫描的体表剂量,为儿童CT检查的防护提供依据。方法 利用模体及热释光剂量计进行测量。结果 儿童头部CT扫描其中心体表剂量平均达19.34 mGy,副鼻窦扫描平均可达43.36 mGy,腹部扫描骨盆部位体表剂量为0.51~2.81 mGy。结论 在满足临床诊断的前提下,应尽量降低扫描分析条件,以减少受照剂量,使儿童的CT应用达到最优化。     

广西CT机头部单层扫描剂量的调查

目的 了解CT机使用过程中患者所接受的辐射剂量。方法 将笔型CT专用电离室置于扫描野中心的头部剂量模体中,以常用的头部条件进行单层扫描,记录剂量仪显示值并将其换算为模体中的剂量指数。结果 全部CT机单层头部扫描剂量均低于国家标准。结论 CT机检查过程中广西境内患者所接受的辐射剂量处于合理水平。     

PET-CT诊断项目工作人员受照剂量及相关场所辐射水平测量与分析

目的 了解PET-CT诊断项目工作人员的受照剂量及相关场所的辐射水平,为降低工作人员受照剂量、完善PET-CT诊断项目放射防护措施提供科学依据。方法 依据国家相关标准,对PET-CT工作场所的周围剂量当量率、表面污染水平和人员受照剂量进行测量;根据相关检测结果与最大工作负荷对手部和眼部剂量进行估算。结果 三家医院PET-CT工作场所辐射水平（0.12~6.05 μSv/h）、β表面污染水平（本底~27.3 Bq/cm²）以及工作人员附加最大年有效剂量（1.58 mSv/a）,符合国家标准规定的限值要求,其中一家医院的分装、注射护士手部最大年当量剂量（154 mSv/a）超出管理目标值（125 mSv/a）。结论 医院应建立针对性的防护措施,提高工作人员的辐射防护意识,降低工作人员所受附加剂量。     

A Comparison of reduction in CT dose through the use of gantry angulations or bismuth shields

This study investigated the effect of gantry angulation and eye shielding on radiation dose to the eye lens during brain Computed Tomography (CT), and secondly the effectiveness of thyroid and breast bismuth shielding during routine neck and chest CT. An anthropomorphic 'Rando' phantom was scanned at three commonly used gantry angles using this centre's normal adult brain protocol, and for normal adult neck and chest protocols. Bismuth shields were placed over the appropriate organs and dose measured using thermoluminescent dosimeters (TLD). Angling the gantry along the supraorbital meatal plane could reduce the dose by approximately 88% relative to the hard palate and Reid's base line protocols. Bismuth eye shields reduce dose by up to 48% when using either of the first two angles but gave no significant reduction in the supra-orbital plane. Reduction in thyroid dose for neck and chest scans were 55% and 47% respectively, and dose reduction in breast was 23%. We thus conclude that angling the gantry to avoid the orbits is the more effective method of reducing radiation dose to the eyes, with single use bismuth shields to be used where this is not feasible. Thyroid and breast shields should be used where the resultant artefact is not detrimental to image quality.     

Fifteen years of radiological protection experience in a regional radiopharmacy

Radiological protection experience in a regional radiopharmacy, currently handling 28.5 TBq (770 Ci) 99mTc y-1, is reviewed for the period 1974-1988. The results of personnel monitoring have shown a downward trend (by more than a factor of two) in radiation exposure of individual staff members, despite the workload per person [6000 GBq (162 Ci) 99mTc y-1] remaining virtually constant. Adequate staff selection and training contribute to the reduction in dose. A significant reduction in dose to the eyes was achieved by installing lead glass screens in the radiopharmacy work stations, and tungsten syringe shields reduced radiation dose to the hands. The use of commercially available kits for producing 99mTc radiopharmaceuticals, rather than relying on in-house preparations that require more operator handling, has also contributed to reduction in radiation exposure. Internal contamination of staff members with 125I was markedly reduced when the practice of sub-dispensing high-specific activity solutions of the radionuclide was discontinued. Annual doses from external radiation currently average less than 6 mSv (600 mrem) to the trunk, less than 7 mSv (700 mrem) to the eyes, and 50 mSv (5 rem) to the hands. Internal contamination of personnel with 125I, 131I, and 99mTc, as detected by thyroid and whole-body monitoring, contributed less than 65 mSv y-1 (6.5 rem) to the thyroid gland and less than 0.1 mSv y-1 (10 mrem) to the whole body.     

Effect of bedside shielding on air-kerma rates around gynecologic intracavitary brachytherapy patients containing 226Ra or 137Cs

An anthropomorphic phantom was implanted with 226Ra or 137Cs gynecologic intracavitary brachytherapy sources. Air-kerma rate measurements were taken at 10-cm increments along a horizontal plane from the side of the bed at 50 cm, 87 cm, and 136 cm heights above the floor. Five portable lead shields were placed at the head, at the foot and along one side of the bed and readings were taken again at the corresponding heights above, below and behind the shields. The readings were normalized to 100-mg Ra equivalence, and air-kerma rate curves were drawn allowing for the comparison of 226Ra and 137Cs with and without lead shields. The data demonstrated that the air-kerma rates for 137Cs were reduced more than those for 226Ra with the use of the portable lead shields. There was four times the transmission with 226Ra than with 137Cs. The optimal placement was with the lateral bedside shields proximal to the head and foot closest to the bed, with the middle shield overlapping in back. The shields at the head and foot should extend out and overlap the bedside shields. The level of the sources should be positioned near the bottom of the shields. This information will provide the medical health physicist with an estimate of air-kerma rates for both 226Ra and 137Cs with and without shielding for evaluating personnel exposures as well as the effectiveness of current shielding in relation to radiation protection requirements in adjacent rooms or hallways.     

Evaluation of patient and staff doses during various CT fluoroscopy guided interventions

As CT scanners are more routinely used as a guidance tool for various types of interventional radiological procedures, concern has grown for high patient and staff doses. CT fluoroscopy provides the physician immediate feedback and can be a valuable tool to dynamically assist various types of percutaneous interventions. However, the fixed position of the scanning plane in combination with high exposure factors may lead to high cumulative patient skin doses that can reach deterministic threshold limits. The staff is also exposed to a considerable amount of scatter radiation while standing next to the patient during the procedures. Although some studies have been published dealing with this subject, data of patient skin doses determined by direct in vivo dosimetry remains scarce. The purpose of this study is to quantify and to evaluate both patient and staff doses by direct thermoluminescent dosimetry during various clinical CT fluoroscopy guided procedures. Patient doses were quantified by determining the entrance skin dose with direct thermoluminescent dosimetry and by estimating the effective dose (E). Staff doses were quantified by determining the entrance skin dose at the level of the eyes, thyroid, and both the hands with direct thermoluminescent dosimetry. For a group of 82 consecutive patients, the following median values were determined (data per procedure): patient E (19.7 mSv), patient entrance skin dose (374 mSv), staff entrance skin dose at eye level (0.21 mSv), thyroid (0.24 mSv), at the left hand (0.18 mSv), and at the right hand (0.76 mSv). The maximum recorded patient entrance skin dose stayed well below the deterministic threshold level of 2 Gy. Poor correlation between both patient/staff doses and integrated procedure mAs emphasizes the need for in vivo measurements. CT fluoroscopy doses are markedly higher than classic CT-scan doses and are comparable to doses from other interventional radiological procedures. They consequently require adequate radiation protection management. An important potential for dose reduction exists by limiting the fluoroscopic screening time and by reducing the tube current (mA) to a level sufficient to provide adequate image quality.     

某医院心内科介入术者受照剂量监测分析

目的 了解某院心血管内科介入手术第一术者在手术过程中的受照剂量,为提高介入术者的辐射防护提供参考依据。方法 选择广西某院心血管内科5名介入手术第一术者为研究对象,按照国家标准《职业性外照射个人监测规范》（GBZ 128—2016）,用热释光剂量计（TLD）监测介入术者的眼晶状体、左小手指、右小手指、左脚踝、甲状腺、左胸、会阴等共7个部位,记录每名术者的受照时间、手术例数、受照剂量,分别计算铅防护衣对X射线的衰减率,评估铅防护衣的屏蔽防护效果。结果 各监测部位受照剂量最高值分别为：眼晶状体2.04 mSv,左小手指为7.22 mSv,右小手指2.40 mSv,左脚踝为0.736 mSv,甲状腺为0.204 mSv,左胸0.054 mSv,会阴0.032 mSv;甲状腺、左胸部、会阴等部位铅防护衣对X射线衰减率平均值由高到低排序为：会阴（91.4%）、左胸部（85.1%）、甲状腺（71.2%）。结论 预估算,眼晶状体年受照剂量为24.5 mSv;除眼晶状体外,其余监测部位的年受照剂量均不超过国家标准限值,介入术者使用个人防护用品,可有效降低其受照剂量,应强化术者自身防护意识,正确使用个人防护用品,提高介入手术操作技术水平,减少不必要的照射。     

某医院SPECT/CT建设项目职业病危害放射防护控制效果评价

目的评价某医院Precedence 16 SPECT/CT建设项目职业病危害放射防护的控制效果。方法依据国家相关放射卫生防护标准和方法,考虑建设项目涉及的2种辐射源:放射性药物(99mTc)产生的γ射线和CT中的X射线,对建成后项目工作场所的周围辐射水平进行检测评价和防护效果进行综合评估。结果不同岗位放射工作人员受照剂量不同,注射室护士手部(4 mSv/a),扫描室操作技师(0.1 mSv/a),给病人摆位技师(2.5 mSv/a)。结论该项目放射防护屏蔽效果良好,符合国家相关标准的要求。     

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。     

CT扫描野内表面防护不同材料的防护效果以及对图像质量的影响

目的 评价两种表面防护材料在CT扫描野内的辐射防护效果和扫描野的图像质量。方法 使用CTDI模体测量颈部扫描时周边的辐射量及CTDI_w,采用铋屏蔽和硫酸钙屏蔽为辐射防护材料的辐射量及CTDI_w,比较有无屏蔽以及两种屏蔽的防护效果差异。低剂量CT筛查60例,随机分为3组,分别为无屏蔽组以及使用铋屏蔽和硫酸钙屏蔽防护组,自动曝光控制扫描,管电压100 kV,参考管电流为23 mAs。对患者甲状腺和肺尖层面的图像质量评分,比较屏蔽对图像质量的影响。结果 模型研究中,无屏蔽组的探测点辐射量为6.17±0.21 mGy;小于床板侧（7.61±0.14）mGy和中心侧为（7.14±0.11）mGy（P<0.01）;而屏蔽组CTDI_w均小于无屏蔽组,且铋屏蔽组和硫酸钙屏蔽组与无屏蔽组CTDI_w分别为5.78、5.02、6.92 mGy（P<0.05）。临床研究中,3组低剂量筛查的有效剂量分别为（0.92±0.05）、（0.90±0.06）、（0.90±0.05）mSv（P>0.05）。3组甲状腺和肺尖成像质量均可满足诊断要求,且屏蔽组的甲状腺成像质量评分明显低于无屏蔽组（F=14.69,P<0.01）,其中硫酸钙屏蔽组评分最低;3组肺尖图像质量评分间差异没有统计学意义（F=1.57,P>0.05）。结论 铋屏蔽与硫酸钙屏蔽均可以作为肺癌CT筛查的甲状腺表面屏蔽使用,不影响肺组织诊断。     

CT非扫描区域防护方法的研究

目的 对CT检查中非扫描区域敏感组织器官的防护方法进行分析和研究。方法 通过分析非扫描区域受到辐射的原因,针对受到辐射的原因逐一提出防护方案。结果 放射卫生管理方面应增强人员防护意识,规范机房内外环境,完善规章制度。使用先进技术进行操作扫描,防护方式分为体表屏蔽、源项屏蔽和体内屏蔽三种。体表屏蔽需要选择先进的屏蔽材料,使用大于0.5 mm铅当量的个人防护用品。源项屏蔽的方法在CT机架孔径正反两侧架设屏蔽,极大地降低了到达非扫描区域的漏射线和外散射线。体内屏蔽通过口服硫酸钡增加人体消化道内局部密度衰减体内的内散射线。源项屏蔽和体内屏蔽的可行性与实用性需进一步通过实验验证。结论 对于CT检查时非扫描部位敏感组织器官的防护应当以"重视操作和防护技术,加强放射卫生管理"的原则为指导;在CT操作方面,在满足影像质量的条件下,选择低剂量扫描方式。在防护技术方面,应依照"衰减漏射线,屏蔽散射线"的理念进行防护。