北京市医用X线诊断剂量水平的研究

本文报道了全国医疗照射剂量水平研究北京试点工作概况和主要特点.北京试点研究利用LiF(Mg,Gu,P)热释光剂量计和自制的可布放25～106个热释光剂量计的专用测量衣,分层抽样监测了75所医院的4383例受检者的体表照射量及其分布。同时,还测量和调查了医用诊断X线半值层和平均投照条件.进而通过体模实验求得受检者体表照射量与器官剂量之间的转换系数,得到了26类主要X线诊断1人次检查的器官剂量和加权剂量当量,估算了北京市X线诊断所致公众剂量负担.其中,每人次检查的平均加权剂量当量以消化道造影最高,对男女分别达12.51和12.71mSv;而每人次门诊脚透,对男女分别为0.37和0.31mSv.各种x线诊断所致北京全民的集体加权剂量当量为3631Sv人/年;人均加权剂量当量为0.39mSv/年。     

湖南省居民医用X线诊断检查的集体剂量当量

本文报道了湖南省居民医用X线诊断检查的集体剂量当量.通过分层抽样调查,共调查了X线机123台,51所医院,4787例。测量了七种类型x线诊断检查时病人的年均体表照射量,并估算了病人主要器官或组织的平均剂量当量和有效剂量当量.1986年湖南省七种类型X线诊断检查总集体加权有效剂量当量约为89.43人·Sv,每次X线检查人均加权有效剂量当量为0.64mSv,湖南省X线诊断检查所致居民有遗传意义剂量和居民平均骨髓剂量分别为0.04mGy和0.38mGy。     

核设施流出物照射人体器官的当量剂量和有效剂量的 …

目的 研究在核设施流出物照射条件下ＩＣＲＰ６０喉出版物建议的新辐射量算法和有关参数，建立在核设施防护领域应用新辐射量的剂量学资料。方法 采用ＡＤＡＭ和ＥＶＡ拟人计算模型和组织－经的方法计算器官当量剂量和有效剂量。结果 给出了人核设施正常运行和事故时可能释放的近２００种核素，在空气浸没，水中浸没和地表沉积物３种照射方式下，器官当量剂量率因子和有效剂量率因子，考虑了男性１８种和女性２０种器官；有效剂量     

湖南省X线胸部诊断检查受检者的体表照射量

根据湖南省各种容量x线机及各类医院抽样,通过门诊胸透1934例(男114l侧、女793例),群检胸透适546例(男249例、女297例)、胸片摄影550例(男339例、女211例)受检者的体表照射量测定,得到全省x线胸部诊断检查时受检者的平均体表照射量.门诊胸透一次,受检者参考点处照射量平均值为1.1伦,群检胸透一次为0.7伦,胸片摄影一次为0.07伦.讨论了x线机防护条件对胸透照射量的影响.及胸片摄影条件对照射量的影响.     

中心层左右径在儿童胸部CT体型特异性剂量测量中的应用

【摘要】目的：比较容积CT剂量指数(CTDIvol)与体型特异性剂量估算（SSDE）两种测量方法测得的辐射剂量在儿童胸部CT检查中的差异。方法：回顾性分析2020年1月至2021年8月行胸部CT检查的131例儿童的病例资料，所有患儿图像均能满足诊断要求。根据患儿图像中心层面的左右径（LAT）进行分组：A组LAT＜20cm，22例；B组20≤LAT<23cm,20例；C组23≤LAT<26cm,21例；D组26≤LAT<29cm，25例；E组29≤LAT<32cm，23例；F组LAT≥32cm，20例。测量患儿胸部中心层CT图像的最大左右径，手动勾画体表最小的范围，不包括检查床床板，测量平均CT值、面积，记录患儿的CTDIvol，并计算转换因子fWED和SSDE，比较 CTDIvol与SSDE的差异。结果：各组的左右径（LAT）、转换因子(fWED)、水当量直径(WED)差异均有统计学意义（P值均＜0.05）。6组CTDIvol与SSDE差异度依次为223.06%、213.01%、203.44%、181.58%、173.58%、157.87%。各组CTDIvol与SSDE均呈正相关。结论：儿童胸部CT检查中，CTDIvol较SSDE低估了患儿的辐射剂量，且患儿中心层面左右径越小，被低估的辐射剂量越大。     

腹部透视病人体表剂量与器官吸收剂量关系的研究

本文介绍了用实验方法得出不同照射条件下的腹部透视器官典型位置皮肤剂量到吸收剂量转换系数值.典型照射条件下的转换系数(mSv/mGy)为:辜丸0.002,卵巢0.019、乳腺<0001、红骨髓0.043,肺<0.001,骨表面0.0079、甲状腺<0.001、其余组织0.012;并采用Drexler等人给出的权重因子得出了加权剂量当量转换系数.本文结果认为,在用体表受照剂量估算器官吸收剂量时,应考虑到照射条件的因素,以免高估或低估器官吸收剂量。     

X射线诊断所致受检者体表剂量分布特性研究

目的　调查常用X射线诊断所致受检者体表剂量 (ESD)的现状 ,为探索建立放射诊断的医疗照射指导水平提供依据。方法　用聚甲基丙烯酸甲酯塑料模体和平板型电离室对 14种检查的ESD进行普查。结果　 14种X射线诊断所致受检者ESD的平均值均未超过IBSS的相应值 ,有 8种投照的剂量分布为对数正态分布。结论　控制受检者入射体表剂量是医疗照射防护最优化的重要内容 ,应尽快建立适合我国国情的指导水平     

基于中国参考人的典型CT扫描患者剂量模拟与分析

目的 基于中国参考人体模,对典型CT患者剂量进行模拟与分析。开发一款在线评估CT扫描所致受检者器官吸收剂量和有效剂量的软件,为快速评估CT扫描辐射剂量提供工具。方法 采用蒙特卡罗方法,对GE LightSpeed 16型号CT进行建模,基于中国参考人体模计算中国成年男性、女性和1岁儿童受CT扫描照射后各组织器官的剂量,建立单层轴扫器官剂量数据库。开发基于web的CT剂量评估软件,根据用户输入的CT扫描参数,从器官剂量数据库中读取数据并快速计算器官吸收剂量和有效剂量。结果 开发了一款新的CT扫描剂量评估软件,可用于评估中国成年男女和1岁儿童在不同型号CT检查中,不同管电压、管电流、准直器宽度等CT参数下的器官剂量。CT扫描剂量评估软件的计算结果与两个文献数据进行对比,对于完全包含在扫描范围内的器官剂量差异较小,相对差异分别在15%和25%以内。结论 CT扫描剂量评估软件为简单快速评估CT扫描辐射剂量提供了有力的工具。     

X射线诊断所致受检者体表剂量分布特性研究

目的　调查常用X射线诊断所致受检者体表剂量 (ESD)的现状 ,为探索建立放射诊断的医疗照射指导水平提供依据。方法　用聚甲基丙烯酸甲酯塑料模体和平板型电离室对 14种检查的ESD进行普查。结果　 14种X射线诊断所致受检者ESD的平均值均未超过IBSS的相应值 ,有 8种投照的剂量分布为对数正态分布。结论　控制受检者入射体表剂量是医疗照射防护最优化的重要内容 ,应尽快建立适合我国国情的指导水平     

儿童胸部和腹部CT:基于42例病人模型的器官剂量评估

正目的评估儿童胸部和腹、盆腔CT检查时器官所受剂量,并评估器官剂量系数对病人体积大小和CT扫描模式的依存度。材料与方法本研究符合HIPAA法案并由机构     

有效剂量与有效剂量当量的异同

本文作者主要讨论ＩＣＲＰ６０号出版物中提出的有效剂量，与ＩＣＲＰ２６号出版物中的有效剂量当量，在概念和使用上比较它们的异同。     

多层螺旋CT肺部低剂量与常规剂量检查的放射剂量评估

目的比较多层螺旋CT肺部低剂量与常规剂量检查的X线辐射剂量,为低剂量多层螺旋CT普查早期肺癌提供剂量参数. 资料与方法肺部低剂量与常规剂量多层螺旋CT扫描共54例.其中,低剂量扫描24例,扫描参数为:120 kV,20 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周;常规剂量扫描30例,扫描参数为:120 kV,90 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周.观察并计算两种扫描剂量的权重CT剂量指数(CTDIw),有效mAs,总mAs,剂量长度乘积(DLP)及有效辐射剂量. 结果肺部低剂量扫描的CTDIw为1.38 mGy,是常规剂量扫描(6.21 mGy)的22.2%;低剂量扫描的DLP为44 mGy*cm,明显低于常规剂量扫描的189 mGy*cm(P＜0.01);低剂量扫描的总mAs为459,是常规剂量扫描(1 308)的35.1%;低剂量扫描的X线最大有效辐射剂量为0.9 mSv,明显低于常规剂量扫描的4.2 mSv(P＜0.01). 结论多层螺旋CT肺部低剂量扫描(20 mAs)的有效辐射剂量为常规剂量扫描的21.4%,适用于高危人群普查早期肺癌.     

Radiation exposure to premature infants in a neonatal intensive care unit in Turkey

OBJECTIVE: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. MATERIALS AND METHODS: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESD(TO)) (n = 23) and from the use of thermoluminescent dosimetry (ESD(TLD)) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESD(TO) by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESD(TO) and ESD(TLD) were correlated using linear regression analysis. RESULTS: The mean ESD(TO) for the chest and abdomen were 67 microGy and 65 microGy per procedure, respectively. The mean ESD(TLD) per radiograph was 70 microGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 microGy) per radiograph. Mean effective doses were 16 and 27 microSv per procedure for the chest and abdomen, respectively. ESD(TLD) was well correlated with ESD(TO) obtained from the total chest and abdomen radiographs for each infant (R(2) = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 x 10(-6) to 2 x 10(-6) and 0.6 x 10(-6) to 2.9 x 10(-6) for chest and abdomen radiographs, respectively. CONCLUSION: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.     

Size-specific dose estimates: Localizer or transverse abdominal computed tomography images?

AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography (CT) images on Size Specific Dose Estimate.METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations (58 ± 13 years, Male:Female 28:22) were included in this study. Anterior-posterior (AP) and lateral (Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph (simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter (√ AP * Lat) to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDI_vol) recorded from the dose reports. Data were analyzed using SPSS v19.RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11% (278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm (range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3% (80/2488) of measurements. SSDE values were significantly different compared to CTDI_vol, ranging from 32% lower to 74% greater than CTDI_vol.CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDI_vol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.     

A review of dosimetry used in epidemiological studies considered to evaluate the linear no-threshold (LNT) dose-response model for radiation protection

Abstract

Background: Accurate dosimetry is key to deriving the dose response from radiation exposure in an epidemiological study. It becomes increasingly important to estimate dose as accurately as possible when evaluating low dose and low dose rate as the calculation of excess relative risk per Gray (ERR/Gy) is very sensitive to the number of excess cancers observed, and this can lead to significant errors if the dosimetry is of poor quality. By including an analysis of the dosimetry, we gain a far better appreciation of the robustness of the work from the standpoint of its value in supporting the shape of the dose response curve at low doses and low dose rates. This article summarizes a review of dosimetry supporting epidemiological studies currently being considered for a re-evaluation of the linear no-threshold assumption as a basis for radiation protection. The dosimetry for each study was evaluated based on important attributes from a dosimetry perspective. Our dosimetry review consisted of dosimetry supporting epidemiological studies published in the literature during the past 15 years. Based on our review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. The article describes the results of our review, explaining which studies clearly stand out for their strengths as well as common weaknesses among all investigations.

Purpose: To summarize a review of dosimetry used in epidemiological studies being considered by the National Council on Radiation Protection and Measurements (NCRP) in an evaluation of the linear no-threshold dose-response model that underpins the current framework of radiation protection.

Materials and methods: The authors evaluated each study using criteria considered important from a dosimetry perspective. The dosimetry analysis was divided into the following categories: (1) general study characteristics, (2) dose assignment, (3) uncertainty, (4) dose confounders (5) dose validation, and (6) strengths and weaknesses of the dosimetry. Our review focused on approximately 20 studies published in the literature primarily during the past 15 years.

Results: Based on the review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. This paper describes the results of our review, identifies common weaknesses among all investigations, and recognizes studies that clearly stand out for their overall strengths.

Conclusions: The paper concludes by offering recommendations to investigators on possible ways in which dosimetry could be improved in future epidemiological studies.     

大剂量增强MR检查对脑部病变的诊断价值

探讨大剂量增强ＭＲ检查对显示脑部隐匿性小病灶以及改善病灶的显示和诊断的准确性。材料与方法：７４例脑部病变包括肺癌脑转移,乳腺癌脑转移,爱滋病脑弓形体病,胶质母细胞瘤,脑膜瘤,分别进行标准剂量和大剂量增强ＭＲ检查,两次查间隔时间不超过３天。     

CT Radiation Dose Optimization and Estimation: an Update for Radiologists

In keeping with the increasing utilization of CT examinations, the greater concern about radiation hazards from examinations has been addressed. In this regard, CT radiation dose optimization has been given a great deal of attention by radiologists, referring physicians, technologists, and physicists. Dose-saving strategies are continuously evolving in terms of imaging techniques as well as dose management. Consequently, regular updates of this issue are necessary especially for radiologists who play a pivotal role in this activity. This review article will provide an update on how we can optimize CT dose in order to maximize the benefit-to-risk ratio of this clinically useful diagnostic imaging method.     

Strategies for reduction of radiation dose in cardiac multislice CT

Because cardiac computed tomography (CT) (mainly coronary CT angiography) is a very promising technique, used more and more for coronary artery evaluation, the benefits and risks of this new low-invasive technique must be balanced. Radiation dose is a major concern for coronary CT angiography, especially in case of repeated examinations or in particular subgroups of patients (for example young female patients). Radiation dose to patient tends to increase from 16- to 64-slice CT. Radiation exposure in ECG-gated acquisitions may reach up to 40 mSv; considerable differences are attributable to the performance of CT machines, to technical dose-sparing tools, but also to radiological habits. Setting radiation dose at the lowest level possible should be a constant goal for the radiologist. Current technological tools are detailed in regard to their efficiency. Optimisation is necessary, by a judicious use of technological tools and also by individual adaptation of kV or mAs. This paper reviews the different current strategies for radiation dose reduction, keeping image quality constant. Data from the literature are discussed, and future technological developments are considered in regards to radiation dose reduction. The particular case of paediatric patients with congenital heart disease is also addressed.     

数字乳腺X射线摄影中管电流量优化的实验研究

目的:探讨数字乳腺X射线摄影中不同靶/滤过组合时降低管电流量(mAs)对图像质量与辐射剂量的影响。方法:不同靶/滤过组合时,以自动曝光模式(AEC)的mAs为基础,分别降低10%、20%、30%、40%、50%时对厚度为4.4 cm的模体进行曝光,测量所得图像的对比噪声比(CNR)、信噪比(SNR)、品质因子(FOM)...     

加速器机载kV锥形束CT有效剂量的分析

目的 分析医用直线加速器机载kV锥形束CT扫描过程中患者的有效剂量随扫描条件的变化.方法 用PTW TM30009电离室分别在T40017头模和T40016躯干模体中,改变XVI锥形柬CT的管电压、毫安秒、准直器以及机架旋转范围等参数测量加权CT剂鼍指数,计算相应的剂量长度乘积和有效剂量.结果 kV锥形束CT的加权剂量指数和有效剂量随管电压呈二次方变化,随毫安秒线性变化,与准直器以及机架旋转范围密切相关.临床常用条件下,kV锥形束CT单次扫描的剂最长度乘积和有效剂量低于参考剂量水平.结论 锥形束CT扫描过程中患者接受的有效剂量与扫描条件密切相关.锥形束CT扫描时,应该根据患者的解剖部位合理选择成像参数,最大限度减少患者接受剂量.