加强放射诊断辐射剂量管理的必要性及应对策略

近年来, 我国放射诊断检查特别是CT检查的频次迅猛增加, 已经成为国民人均辐射剂量的最大人工辐射来源, 并有可能超过天然辐射源的贡献。临床诊疗活动中, 患者和受检者短时间内可能进行多项目、多频次的放射诊断成像, 所接受的累积辐射剂量较高, 甚至一天检查的剂量贡献超过50或100 mSv, 从而对其健康产生潜在风险。因此, 有必要对放射诊断辐射剂量信息进行统计分析与控制管理, 以尽可能降低过高剂量及其辐射危险的发生概率。本文对放射诊断辐射风险的国际认识、我国放射诊断设备和检查频次、放射诊断辐射剂量及其管理现状进行阐述, 并就辐射剂量的管理提出应对策略, 为进一步推进临床实践中的辐射防护提供参考。     

Radimetrics在放射剂量管理中的研究与进展

【摘要】随着CT影像技术的不断发展与进步,CT检查应用越来越广泛,其在临床诊断中起着不可或缺的作用。 但CT的辐射剂量较大,世界各国的医疗辐射特别是CT的辐射剂量仍在持续增加,如何使CT辐射剂量得到合理的管控,同时获得更优的成像质量已经成为大家关注的重点。Radimetrics放射剂量管理软件能够很好地调控与优化剂量管理。本文就Radimetrics在放射剂量管理中的研究与进展进行阐述。     

运用内置化蒙特卡罗模拟对心电触发管电流调节和螺距匹配技术对双源CT冠状动脉成像辐射剂量的思考:

目的评估临床常规接受双源CT冠状动脉成像(CTA)病人所受到的辐射剂量水平。方法运用心电触发管电流调节(TCM)功能和依赖心率的螺距匹配技术,对56例病人行冠状动脉CTA检查。个体化蒙特卡罗(MC)模拟用于剂量评估。固定管电流的回顾性模型(CTC)作为参考。肺组织     

双源CT颈动脉血管造影两种扫描方式的辐射剂量比较

CT的辐射剂量和图像质量一直是生产厂家、放射学工作者关注的重点问题之一~([1]).随着临床CT检查的普及,CT的辐射剂量在所有放射成像影像设备中所占的比重越来越大,这就要求尽量降低受检者的辐射剂量.     

高能光源储存环及同步加速器屏蔽计算与探讨

目的 验证和探讨在高能同步辐射光源辐射屏蔽计算中半经验公式和蒙特卡罗模拟方法的一致性和适用性.方法 分别采用半经验公式和蒙特卡罗模拟独立计算单电子打靶时屏蔽体外产生的周围剂量当量.结果 Jenkins半经验公式计算结果与蒙特卡罗模拟结果比值范围为111％～153％,Sakano半经验公式计算结果与蒙特卡罗模拟结果比值为...     

放射外照射事故剂量重建中的蒙特卡罗模拟方法

目的 建立放射外照射事故剂量重建的计算机系统。方法 基于MIRD的人体及其器官的数学模型，采用蒙特卡罗(MC)方法，结合 放射事故的受照模式，建立放射外照射事故剂量重建的计算机系统。结果 成功研制了放射事故剂量重建的计算机系统。用这个系统计算了河南省^60Co放射事故危重病人的剂量，其计算结果与实验模拟测量和生物剂量检测结果十分一致。结论 本系统方便、快捷，它不但可估算事故受照人员的器官剂量和全身剂量，而且也能用于事故早期剂量的估计。     

应警惕介入手术操作时眼晶状体所受的辐射剂量

目的评估放射介入从业人员眼晶状体在使用放射防护和未使用放射防护状态下所接受的辐射剂量。材料和方法采用模拟模具测量7种放射介入透视系统的散射辐射     

用蒙特卡罗方法估算~(60)Co辐射源事故患者的辐射剂量

目的　计算河南6 0 Co放射源事故中事故患者“梅”受到的辐射剂量。方法　基于MIRD的成人数学模型用蒙特卡罗随机模型方法计算事故患者的辐射剂量 ,并编制了一个用于此计算实用计算机程序。结果　模拟事故患者的具体情况 ,计算了人体主要器官剂量和全身剂量。结论　这种理论模拟的方法与用体模的实验模拟测量结果较为一致 ,说明用这种算法算出的各个器官剂量和全身剂量 ,对于临床治疗有参考价值 ,而且模拟方便 ,快速 ,适用于核事故医学应急中的患者器官剂量估算。     

冠状动脉CT血管造影辐射剂量蒙特卡罗软件模拟计算及仿真体模验证

目的 应用蒙特卡罗（Monte Carlo）数学模型计算冠状动脉CT血管造影（CCTA）检查中患者的辐射剂量,并验证其准确性和有效性。方法 采用3组管电压（80、100、120 kV）对人体仿真体模行双源CT检查,使用数学模型软件（ImpactDose 2.0）模拟方法测量CCTA 3组管电压的患者器官吸收剂量并转换有效剂量,采用人体仿真体模置入热释光剂量计实验对数学模型模拟的结果进行验证。结果 除肺部以外,利用蒙特卡罗软件模拟计算的所有器官剂量值均小于利用仿真体模测量的;两种方法的相对误差在±50％以内。结论 利用蒙特卡罗软件模拟计算CCTA患者辐射剂量误差在可接受范围内,可用于估算CCTA检查辐射剂量水平。     

定位像在自动管电流调制技术胸部CT的器官剂量方面的影响

正摘要目的评估定位像对胸部总辐射剂量的影响,包括定位像剂量和随后应用管电流调制技术(TCM)进行胸部CT检查的剂量。材料与方法采用带和不带有不同尺寸乳腺附件的192层CT扫描模拟人体模型,进行前后(AP)或后前位(PA)定位像检查和应用TCM的胸部CT检查。基于获得的CT数据,通过蒙特卡罗模拟得到剂量分布。采用蒙特卡罗模拟的定位像扫描时,球管位置固定在0°和180°;胸部CT采用TCM技术的螺旋扫描。通过采用固定起始角(0°、90°和180°)的TCM曲线和蒙特卡罗模拟来研究球管起始角度对     

Radiation absorbed doses at compact bone-titanium interfaces in diagnostic radiography: a Monte Carlo approach

OBJECTIVES: The aim of this study was to estimate the radiation absorbed dose at cortical tissue-implant interfaces in diagnostic radiology. METHODS: Since our interest was the radiation dose at an interface (cortical bone-implant interface), a Monte Carlo simulation was considered to be the most suitable method for studying the problem. The Monte Carlo code employed was MCNP4B. A phantom consisting of soft tissue, cortical bone, an implant and air, with appropriate chemical compositions and densities, was described in the code. The implant simulated had a commercial name of ASTM67, grade 2 and was 1.9 mm wide. The incident photon beam was divergent of 20 cm x 20 cm at a source-to-phantom distance of 40 cm. Two energy spectra were employed (70 kVp and 100 kVp, 0.5 mm Al internal filtration) and their photon fluence distribution against energy was described in the code with an energy interval of 5 keV. The computations that led to radiation dose calculations had a spatial resolution of 0.01 cm (100 microm) to allow a detailed radiation dose distribution across the cortical bone-titanium interface. Monte Carlo runs took place both with and without an implant in the phantom and, in each case, 120 million photon histories were followed, leading to a radiation dose statistical fluctuation between 5% and 10%. RESULTS: The ratio of radiation dose with implant to dose without implant against depth allows a direct estimate of the effect of the implant on the radiation dose to the cortical bone surrounding the implant. At a distance >or=100 microm there was no radiation dose increase due to the titanium implant. However, in contact with the implant (i.e. the first layers of cells) there was a sharp radiation dose increase as high as 3.5 times the radiation dose compared with when the implant was absent. Also, the newly formed bone inside the implant's tiny hole received a radiation dose close to 50% of the radiation dose without the implant owing to high absorption by the implant itself. CONCLUSIONS: Assuming that the patient received five radiographic images over a 6-month period, the maximum radiation dose at the cortical bone-titanium interface was estimated to be less than 20 mGy (0.02 Gy).     

用蒙特卡罗方法估算60Co辐射源事故患者的辐射剂量

目的：计算河南^60Co放射源事故中事故患者“梅”受到的辐射剂量,方法：基于MIRD的成人数学模型蒙特卡罗随机模型方法计算故忠患者的辐射剂量,并编制了一个用用此计算实用计算机程序,结果：模拟事故患者的具体情况,计算了人体主要器官剂量和全身剂量,结论：这种理论模拟的方法与用模的实验模拟测量结果较为一致,说明用这种算法算出的各个器官剂量和全身剂量,对于临床治疗有参考价值,而且模拟方便,快速,适用于核事故医学应急中的患者器官剂量估算。     

Equivalent dose to the fetus from occupational exposure of pregnant staff in diagnostic radiology

The protection of the unborn children of pregnant women from ionizing radiations is very important because the fetus is particularly vulnerable to the effects of ionizing radiation. From the radiation protection perspective, the International Commission on Radiological Protection regards the unborn child as a member of the public when considering the occupational exposure of pregnant workers. The determination of the equivalent dose to the unborn child in diagnostic radiology is of interest as a basis for risk estimates from occupational exposures of the pregnant worker. In this paper, coefficients for converting dosemeter readings to equivalent dose to the fetus have been calculated using Monte Carlo simulation. X-ray transport was simulated by tracing individual photons through soft tissue phantoms. Equivalent dose to the uterus was used to simulate the equivalent dose to the fetus during the first 2 months of pregnancy. The Monte Carlo model was validated experimentally by direct measurements made in an Alderson female Rando phantom for a range of irradiation conditions. The two sets of data indicated good agreement with the Monte Carlo results, being relatively greater than the experimental results to a maximum of about 15%.     

Patient radiation exposure in uterine artery embolization of leiomyomata: calculation of organ doses and effective dose

The goal of this study was estimation of patient effective dose from uterine artery embolization of leiomyomata. Parameters and data relevant to patient dose were recorded for 33 consecutive procedures. Using Monte Carlo simulation of radiation transport, organ and effective doses were calculated in detail for a subset of five procedures, to estimate the effective dose for all procedures. Mean dose area product was 59.9, median 23.4, and range 8.8–317.5 Gycm². Mean absorbed ovarian dose was calculated as 51 mGy in the five procedures. Using the dose conversion factor estimated from the Monte Carlo simulation for all procedures a mean estimated effective dose of 34 mSv (median 13 mSv, range 5–182 mSv) results, with a tendency to lower values regarding the succession of the procedures. Patients radiation exposure level is up to twice of that of an abdominal CT examination . Angiographic equipment related dose-reducing features and radiographic technique essentially influence organ doses and effective dose. Consistent application of dose-reducing techniques and awareness of radiation exposure justifies uterine artery embolization as a therapeutic option for the treatment of uterine fibroids.     

蒙特卡罗模拟方法结合不同体模在剂量估算中的应用

随着核与辐射在人们日常生活中的应用越来越广泛,其所带来的危害也备受关注。剂量估算是辐射技术应用的重要一环,估算出人体所受的剂量对评价辐射造成的确定效应与随机效应起着重要作用。蒙特卡罗（MC）模拟与人体参考模型结合可对核事故、医疗照射和环境的辐射剂量进行估算,是一种快速且对硬件要求较少的剂量估算方法,目前正面临模型开发和计算耗时的瓶颈,笔者对此现状进行综述。     

Monte Carlo systems used for treatment planning and dose verification

General-purpose radiation transport Monte Carlo codes have been used for estimation of the absorbed dose distribution in external photon and electron beam radiotherapy patients since several decades. Results obtained with these codes are usually more accurate than those provided by treatment planning systems based on non-stochastic methods. Traditionally, absorbed dose computations based on general-purpose Monte Carlo codes have been used only for research, owing to the difficulties associated with setting up a simulation and the long computation time required. To take advantage of radiation transport Monte Carlo codes applied to routine clinical practice, researchers and private companies have developed treatment planning and dose verification systems that are partly or fully based on fast Monte Carlo algorithms. This review presents a comprehensive list of the currently existing Monte Carlo systems that can be used to calculate or verify an external photon and electron beam radiotherapy treatment plan. Particular attention is given to those systems that are distributed, either freely or commercially, and that do not require programming tasks from the end user. These systems are compared in terms of features and the simulation time required to compute a set of benchmark calculations.     

Monte Carlo simulation for MLC-based intensity-modulated radiotherapy.

This article describes photon beam Monte Carlo simulation for multi leaf collimator (MLC)-based intensity-modulated radiotherapy (IMRT). We present the general aspects of the Monte Carlo method for the non-Monte Carloist with an emphasis given to patient-specific radiotherapy application. Patient-specific application of the Monte Carlo method can be used for IMRT dose verification, inverse planning, and forward planning in conventional conformal radiotherapy. Because it is difficult to measure IMRT dose distributions in heterogeneous phantoms that approximate a patient, Monte Carlo methods can be used to verify IMRT dose distributions that are calculated using conventional methods. Furthermore, using Monte Carlo as the dose calculation method for inverse planning results in better-optimized treatment plans. We describe both aspects and present our recent results to illustrate the discussion. Finally, we present current issues related to clinical implementation of Monte Carlo dose calculation. Monte Carlo is the most recent, and most accurate, method of radiotherapy dose calculation. It is currently in the process of being implemented by various treatment planning vendors and will be available for clinical use in the immediate future.     

Internal radionuclide radiation dosimetry: a review of basic concepts and recent developments.

Internal dosimetry deals with the determination of the amount and the spatial and temporal distribution of radiation energy deposited in tissue by radionuclides within the body. Nuclear medicine has been largely a diagnostic specialty, and model-derived average organ dose estimates for risk assessment, the traditional application of the MIRD schema, have proven entirely adequate. However, to the extent that specific patients deviate kinetically and anatomically from the model used, such dose estimates will be inaccurate. With the increasing therapeutic application of internal radionuclides and the need for greater accuracy, radiation dosimetry in nuclear medicine is evolving from population- and organ-average to patient- and position-specific dose estimation. Beginning with the relevant quantities and units, this article reviews the historical methods and newly developed concepts and techniques to characterize radionuclide radiation doses. The latter include the 3 principal approaches to the calculation of macroscopic nonuniform dose distributions: dose point-kernel convolution, Monte Carlo simulation, and voxel S factors. Radiation dosimetry in "sensitive" populations, including pregnant women, nursing mothers, and children, also will be reviewed.