基于中国儿童参考体模的X射线摄影剂量评估

目的 建立中国儿童面元参考体模,并将其应用于儿童X射线摄影的剂量评估中。方法 基于不同年龄儿童的CT原始数据,经过器官勾画、器官调整优化等过程建立起5和10岁的中国儿童面元参考体模。基于上述体模,利用蒙特卡罗方法,对X射线摄影进行建模,计算不同照射条件下儿童受检者器官剂量转换系数及有效剂量转换系数。结果 建立的5和10岁中国儿童面元参考体模,体格参数符合国家标准要求,器官质量与中国参考人参考值差异在2%以内。计算得到X射线摄影胸部后前位和腹部前后位、管电压60~90 kVp、总滤过2.5~4 mmAl的器官剂量及有效剂量转换系数数据库,有效剂量转换系数与文献结果差异在3%以内。结论 所建立的中国儿童面元参考体模能广泛应用于放射防护研究,其研究结果能够为我国儿童临床X射线摄影剂量评估提供参考数据。     

河南省X射线摄影成年受检者入射体表剂量调查

目的 调查河南省X射线摄影致成年受检者的入射体表剂量水平,为建立适合我国国民体质特征的放射诊断受检者剂量指导水平提供技术和数据支持。方法 采用非概率抽样方法选取河南省郑州、开封和信阳3个地市14家医院,用热释光剂量测量方法调查普通X射线摄影、计算机X射线摄影（CR）和直接数字化X射线摄影（DR）不同照射部位1 404名受检者入射体表剂量水平。结果 河南省普通X射线摄影、CR摄影和DR摄影致成年受检者入射体表剂量范围分别为0.20~47.71、0.16~6.89和0.10~10.41 mGy。腹部前后位（AP）、骨盆AP、头颅侧位（LAT）、头颅后前位（PA）、胸部LAT、胸部PA、胸椎AP、胸椎LAT、腰椎AP、腰椎LAT摄影入射体表剂量范围分别为0.16~10.05、0.20~10.36、0.11~2.13、0.10~2.92、0.39~5.85、0.12~1.82、0.16~11.67、0.36~29.37、0.25~14.49和1.18~47.71 mGy。普通X射线摄影致受检者入射体表剂量高于CR和DR摄影,差异有统计学意义（Z=-8.709、-9.570,P<0.05）。普通X射线摄影胸部PA、腰椎LAT入射体表剂量高于全国“九五”期间调查结果,差异有统计学意义（Z=3.262、2.538,P<0.05）。结论 河南省普通X射线摄影和CR摄影所致受检者胸部PA和LAT入射体表剂量超过医疗照射指导水平,普通X射线摄影部分照射部位入射体表剂量较全国“九五”期间调查结果有所提高。     

计算机X射线摄影剂量指示值与受检者入射体表剂量的关系

目的 研究计算机X射线摄影(CR)中剂量指示值与受检者入射体表剂量之间的关系,建立受检者入射体表剂量的估算方法。方法 以Kodak的CR系统为研究对象,基于理论推导建立受检者入射体表剂量估算模型,通过实验测量确定模型中的重要参数,建立由剂量指示值估算入射体表剂量的方法,并通过实验验证其有效性。结果 用本研究建立的模型计算出的受检者入射体表剂量与实测值之比的平均值为0.97,95%可信区间为0.77~1.18;在比较不同X射线摄影系统时,发现计算值与实测值之间的差异没有统计学意义。 结论 本研究建立的由剂量指示值估算受检者入射体表剂量的模型,可用于快速评估计算机X射线摄影所致受检者的入射体表剂量。     

广西X射线诊断受检者体表入射剂量调查

目的 探讨广西X射线诊断受检者体表入射剂量。方法 分层随机抽样选取25家不同级别医院的2 236例X射线诊断受检者为调查对象,采用热释光剂量测量不同级别的医院、不同类型设备和不同照射部位受检者的体表入射剂量。结果 普通X射线摄影、计算机X射线摄影(CR)和直接数字化X射线摄影(DR)受检者体表入射剂量范围分别为0.08~31.51、0.11~4.25和0.05~35.63 mGy。腹部前后位(AP)、骨盆AP;头颅侧位(LAT)、头颅后前位(PA)、胸部PA、胸部LAT、胸椎AP、胸椎LAT、腰椎AP、腰椎LAT入射剂量范围分别为0.08~19.53、0.15~18.78、0.08~9.87、0.06~9.24、0.05~2.71、0.13~2.93、0.15~19.01、0.07~25.33、0.16~27.23和0.11~35.63 mGy。结论 广西X射线诊断受检者平均入射剂量达标,但部分DR摄影致胸部PA入射剂量超过医疗照射指导水平。     

内蒙古自治区常规X射线诊断患者剂量调查结果分析

目的 分析内蒙古地区常规X射线诊断患者入射体表剂量水平。方法 根据全国医疗照射剂量及频度调查项目方案的要求,完成内蒙古地区30%数量医疗机构常规X射线诊断应用现状调查,按照医疗机构年接诊人数比例抽取内蒙古地区12个盟市24家医疗机构开展普通X射线诊断患者入射体表剂量调查。将不同设备、不同级别医院、不同照射部位间受检者入射体表剂量结果进行比较。结果 在各类诊断设备中,以数字X射线摄影系统（DR）为主。在各类常规X射线诊断检查过程中,腰椎摄影所致患者平均入射体表剂量为3.39 mGy/人,骨盆及髋关节摄影检查所致患者平均入射体表剂量为1.65 mGy/人,颈椎、四肢和胸部摄影所致患者平均入射体表剂量分别为0.90、0.38、0.37 mGy/人。在胸部、腰椎、颈椎3种部位的诊断检查中,使用屏片摄影设备所致受检者入射体表剂量高于DR测量结果,差异具有统计学意义（Z=-3.229、-4.820、-5.265,P<0.05）。结论 屏片摄影设备所致患者的入射体表剂量大于DR,操作人员的操作行为是影响患者入射体表剂量的重要因素。     

X射线胸部摄影曝光剂量与图像质量相关性研究

目的 研究数字化X射线胸部高千伏摄影曝光剂量与图像质量的关系,确定数字化X射线摄影最佳曝光剂量。方法 选择胸部高千伏摄影管电压120 kV,摄影mAs从1 mAs逐档增加至25 mAs,对模拟人体胸部厚度摄影体模与CDRAD 2.0对比度细节体模进行摄影,测量体模表面X射线入射剂量,由5位观察者独立阅读体模影像,比较任意两曝光条件组之间的图像质量因子（IQF）,确定高千伏胸部摄影最佳条件。比较4和10 mAs条件下正常人体胸部摄影图像质量评分。结果 胸部高千伏摄影体模曝光条件从1 mAs增加到25 mAs,体模表面X射线入射剂量从0.067 mGy增加至1.468 mGy。随着X射线入射剂量的增加,影像质量影响因子IQF值不断减小,观察者阅读体模信号的IQF差异有统计学意义（F=31.00,P<0.05）,曝光剂量条件选择在1~4 mAs时所对应的IQF均值差异有统计学意义（F=15.3,P<0.05）,4~10 mAs时所对应的IQF差异无统计学意义,10~25 mAs时所对应的IQF均值差异有统计学意义（F=9.74,P<0.05）。曝光剂量条件选择4和10 mAs所对应的体模表面入射剂量为0.250和0.606 mGy,两种条件下胸部图像质量的综合评分分别为（24.8±1.64）、（25.8±2.05）分,差异无统计学意义。结论 随着数字化X射线摄影剂量的增加所获得图像信息量增加。满足临床诊断的标准人体胸部高千伏数字化X摄影最佳剂量为0.250 mGy左右。     

胸部DR摄影中管电压对影像质量和辐射剂量影响的模体研究

目的 研究胸部数字X射线摄影(DR)中,不同管电压对影像质量以及受检者辐射剂量的影响。方法 管电压在80~130 kV范围内间隔10 kV变化,每种管电压设置下自动曝光控制(AEC)范围在-4~4对成人胸部模体进行曝光。测量模体表面的皮肤入射剂量,计算相对噪声值和对比度噪声比(CNR),并估算每次曝光时受检者的有效剂量。结果 皮肤入射剂量为(0.062 9±0.027 4)mGy,有效剂量为(0.012 7±0.004 5)mSv,有效剂量随着皮肤入射剂量的增加而呈线性增加,两者呈正相关关系(r=0.912,P<0.01)。随着有效剂量的增加,相同管电压下,相对噪声与有效剂量呈负相关关系(r=-0.967、-0.969、-0.968、-0.969、-0.968、-0.970, P<0.01);CNR与有效剂量呈正相关关系(r=0.987、0.987、0.986、0.987、0.988、0.989,P<0.01)。AEC不变时,随着kV值增加,皮肤入射剂量和有效剂量均降低,最大可降低50%和20%;相对噪声值降低,最大可降低23%;CNR增加,最大可增加8%。结论 胸部DR摄影中,在满足影像质量要求的前提下,高kV值可有效降低受检者辐射剂量。     

直接摄影检查患者的照射剂量分析

目的 通过对不同部位直接摄影(DR)检查的医学数字成像和传输(DICOM)文件信息中的患者剂量信息的统计,调查不同投照部位DR摄片的照射剂量分布范围,分析影响DR检查照射剂量的因素。方法 随机选取浙江省某三甲医院2009年1月至4月5160次DR摄片,包括胸部、胸椎及腰椎正、侧位、腹部前后位及骨盆正位。应用软件自动提取每例患者检查中DICOM信息文件中的剂量面积乘积(DAP),并结合照射野的范围,计算各部位DR检查的入射表面剂量(ESD)。结果 腹部前后位、腰椎侧位、胸椎正侧位的变异系数在60%以下;胸部正侧位、腰椎正位、骨盆正位的变异系数为60%~80%。各个部位的DAP最大值与最小值比值,除腹部前后位较小为3倍,其余部位差异较大。其中,腰椎正位最大差别为46倍、腰椎侧位30倍,胸椎侧位、胸部正位、侧位、骨盆正位、胸椎正位分别为23、23、18、16、11倍。通过计算得到ESD值选择75%分位点与现行普通摄片诊断参考水平(DRL)比较后发现,胸部正、侧位分别下降75%和73%;腰椎正侧位下降66%和77%;胸椎正侧位下降85%和84%;骨盆正位下降88%;腹部前后位下降88%。结论 DR检查中各个部位的DAP与ESD值存在较大变动,ESD值与现行的常规摄片的DRL相比有较大下降;有必要回顾分析DR摄片的患者照射剂量,对患者照射剂量与图像质量进行质量管理。     

CR与非晶体硅DR胸部摄影曝光剂量优化的探讨

目的 比较CR与非晶体硅DR在胸部摄影中入射剂量的差异,探讨两者最优化曝光剂量。方法 应用CR、DR分别对胸部模体行不同入射剂量曝光成像,记录模体表面入射剂量,用CDRAD2.0评估软件计算模体影像图像质量因子反数值IQFinv。CR组、DR组图像IQFinv差异用两独立样本t 检验;CR组、DR组各自图像IQFinv与入射剂量的关系应用pearson相关;应用ROC曲线分析获取两组最佳图像IQFinv值,并换算曝光剂量。结果 CR和DR组入射剂量和图像质量IQFinv值之间呈明显的正相关(r =0.893、0.848, P<0.01),并存在线性回归。CR和DR组IQFinv值差异有统计学意义(t =5.455, P<0.05)。ROC曲线分析(曲线下面积AUC＝0.893, P<0.001),最佳IQFinv值为3.55。结论 CR、DR系统对于低对比度细节的检测能力均随着入射剂量的增加而增加。入射剂量相同时,DR系统对于低对比度细节的检测能力优于CR;在获得相同的图像质量时,与CR相比应用DR可大大降低被检者辐射剂量。     

基于人体体素模型的光子外照射事故剂量重建方法研究

目的 研究光子外照射事故下人体的剂量重建方法,并在局部剂量分布层面上验证方法的准确性。方法 基于开源蒙特卡罗代码Geant4,使用国际辐射防护委员会（ICRP）103号建议书推荐的人体体素模型,研究外照射事故照射条件下的剂量重建方法,实现全身平均吸收剂量、器官吸收剂量和局部剂量分布的评价。为了对建立的方法进行验证,使用组织等效的物理仿真模型ART;通过CT扫描,建立起其分辨率为1.57 mm×1.57 mm×10.00 mm的体素模型;在标准辐射场下进行一系列热释光剂量计（TLD）照射实验,比较实验和剂量重建模拟的结果。结果 实验测量值的综合相对不确定度为10.9%,剂量重建模拟值的综合相对不确定度在非组织交界面处为7.10%,在组织交界面处为16.6%。对451个测量点位进行统计分析,模拟值除以测量值的均值为0.972,标准差为0.083 8,在0.95~1.05,0.90~1.10和0.80~1.20范围内的比例分别为49.2%,79.4%和96.4%。结论 基于人体体素模型的蒙特卡罗剂量重建方法无论在全身或器官层面,还是在局部剂量分布层面都满足实际使用的精度要求,可作为外照射事故下对受照者进行剂量评估的有力工具,为诊断和救治提供支持。     

Comparison of internal radiation doses estimated by MIRD and voxel techniques for a "family" of phantoms

The aim of this study was to use a new system of realistic voxel phantoms, based on computed tomography scanning of humans, to assess its ability to specify the internal dosimetry of selected human examples in comparison with the well-established MIRD system of mathematical anthropomorphic phantoms. Differences in specific absorbed fractions between the two systems were inferred by using organ dose estimates as the end point for comparison. A "family" of voxel phantoms, comprising an 8-week-old baby, a 7-year-old child and a 38-year-old adult, was used and a close match to these was made by interpolating between organ doses estimated for pairs of the series of six MIRD phantoms. Using both systems, doses were calculated for up to 22 organs for four radiopharmaceuticals with widely differing biodistribution and emission characteristics (technetium-99m pertechnetate, administered without thyroid blocking; iodine-123 iodide; indium-111 antimyosin; oxygen-15 water). Organ dose estimates under the MIRD system were derived using the software MIRDOSE 3, which incorporates specific absorbed fraction (SAF) values for the MIRD phantom series. The voxel system uses software based on the same dose calculation formula in conjunction with SAF values determined by Monte Carlo analysis at the GSF of the three voxel phantoms. Effective doses were also compared. Substantial differences in organ weights were observed between the two systems, 18% differing by more than a factor of 2. Out of a total of 238 organ dose comparisons, 5% differed by more than a factor of 2 between the systems; these included some doses to walls of the GI tract, a significant result in relation to their high tissue weighting factors. Some of the largest differences in dose were associated with organs of lower significance in terms of radiosensitivity (e.g. thymus). In this small series, voxel organ doses tended to exceed MIRD values, on average, and a 10% difference was significant when all 238 organ doses were considered as a single group. In 12 comparisons of effective dose, the mean voxel to MIRD ratio was 1.07 (range 0.72-1.32). It was shown for the majority of cases that, whereas some large differences in SAF values exist, differences in source organ and effective dose values between the MIRD and voxel methods were largely accounted for by the respective organ mass differences. The reasons for various organ dose differences with the selected radiopharmaceuticals are discussed. Taking biological variation into account, there is reasonable agreement between the two methods but some significant differences exist that warrant further investigation. More extensive comparisons involving a wide variety of voxel phantoms are required to establish whether realistic voxel phantoms should eventually replace the MIRD system.     

Comparison of internal radiation doses estimated by MIRD and voxel techniques for a "family" of phantoms

The aim of this study was to use a new system of realistic voxel phantoms, based on computed tomography scanning of humans, to assess its ability to specify the internal dosimetry of selected human examples in comparison with the well-established MIRD system of mathematical anthropomorphic phantoms. Differences in specific absorbed fractions between the two systems were inferred by using organ dose estimates as the end point for comparison. A "family" of voxel phantoms, comprising an 8-week-old baby, a 7-year-old child and a 38-year-old adult, was used and a close match to these was made by interpolating between organ doses estimated for pairs of the series of six MIRD phantoms. Using both systems, doses were calculated for up to 22 organs for four radiopharmaceuticals with widely differing biodistribution and emission characteristics (technetium-99m pertechnetate, administered without thyroid blocking; iodine-123 iodide; indium-111 antimyosin; oxygen-15 water). Organ dose estimates under the MIRD system were derived using the software MIRDOSE 3, which incorporates specific absorbed fraction (SAF) values for the MIRD phantom series. The voxel system uses software based on the same dose calculation formula in conjunction with SAF values determined by Monte Carlo analysis at the GSF of the three voxel phantoms. Effective doses were also compared. Substantial differences in organ weights were observed between the two systems, 18% differing by more than a factor of 2. Out of a total of 238 organ dose comparisons, 5% differed by more than a factor of 2 between the systems; these included some doses to walls of the GI tract, a significant result in relation to their high tissue weighting factors. Some of the largest differences in dose were associated with organs of lower significance in terms of radiosensitivity (e.g. thymus). In this small series, voxel organ doses tended to exceed MIRD values, on average, and a 10% difference was significant when all 238 organ doses were considered as a single group. In 12 comparisons of effective dose, the mean voxel to MIRD ratio was 1.07 (range 0.72-1.32). It was shown for the majority of cases that, whereas some large differences in SAF values exist, differences in source organ and effective dose values between the MIRD and voxel methods were largely accounted for by the respective organ mass differences. The reasons for various organ dose differences with the selected radiopharmaceuticals are discussed. Taking biological variation into account, there is reasonable agreement between the two methods but some significant differences exist that warrant further investigation. More extensive comparisons involving a wide variety of voxel phantoms are required to establish whether realistic voxel phantoms should eventually replace the MIRD system.     

Equivalent dose to organs and tissues in hysterosalpingography calculated with the FAX (Female Adult voXel) phantom

Hysterosalpingography (HSG) is a radiological examination indicated for investigating infertility or uterine and tubal pathologies. Women who undergo HSG are relatively young, typically between 20 years and 40 years, and equivalent doses to the ovaries are usually reported to be around 4 mSv per examination. A review of studies on patient dosimetry in HSG revealed that almost all absorbed doses to organs and tissues had been calculated with conversion coefficients (CCs) based on hermaphrodite versions of MIRD5-type phantoms. The CCs applied had been taken from data sets for abdominal or pelvic examinations because CCs for HSG examination were not available. This study uses the FAX (Female Adult voXel) phantom in order to calculate equivalent doses to radiosensitive organs and tissues especially for exposure conditions used in HSG. The calculations were also performed for the MIRD5-type EVA phantom to demonstrate the influence of anatomical differences on organ equivalent dose. The results show organ and tissue equivalent doses as a function of the variations of the exposure conditions. At 4.56 mSv the ovarian equivalent dose calculated for the FAX phantom is about 21% greater than the average ovarian equivalent dose reported in the literature, which reflects the anatomical differences between the FAX and the MIRD5-type phantoms.     

Patient absorbed doses in digital grey-scale fluorography

This article describes a preliminary comparison between the levels of patient dose used in digital grey-scale fluorography (DGF) and screen-film radiography. Patient doses were measured in three common radiographic examinations, postero-anterior chest, antero-posterior lumbar spine and lateral lumbo-sacral junction, using thermoluminescent dose-meters and an anthropomorphic phantom. Within the limitations of the image quality currently available in DGF, the findings indicate that digital radiography with the large-field X-ray image intensifier promises significant savings in patient dose compared with conventional radiography.     

Strategies for formulating appropriate MDCT techniques when imaging the chest, abdomen, and pelvis in pediatric patients

OBJECTIVE: Our aim was to formulate appropriate MDCT chest and abdominopelvic CT scan protocols for pediatric patients. MATERIALS AND METHODS: Surface radiation dose measurements from a set of anthropomorphic phantoms (nominal 1 year old, 5 year old, and 10 year old) and an adult phantom were compared with standard CT dose index measurements. Image-noise values on axial 5-mm-thick anthropomorphic phantom images were obtained as a measure of image quality. RESULTS: Peripheral CT dose index values obtained with the standard 16-cm acrylic phantom were within approximately 10% of the CT surface dose measurements for the pediatric anthropomorphic phantoms for both chest and abdominopelvic scan protocols. The noise value for the adult phantom image acquired using a typical clinical CT technique was identified, and targeting this level of noise for pediatric CT examinations resulted in a decrease in dose of 60-90%. Initially, 80 kVp was selected for use with very small children; however, beam-hardening artifacts were severe enough to cause us to abandon this option. Current pediatric protocols at M. D. Anderson Cancer Center rely on 100- and 120-kVp settings. The display field-of-view parameter can be used as a surrogate for patient size to develop clinical pediatric CT protocol charts. CONCLUSION: CT dose index measurements obtained using the 16-cm standard acrylic phantom are sufficiently accurate for estimating chest and abdominopelvic CT entrance exposures for pediatric patients of the same approximate size as the anthropomorphic phantoms used in this study. Image-noise measurements can be used to adjust chest and abdominopelvic CT techniques for pediatric populations, resulting in a decrease in measured entrance dose by 60-90%.     

Organ and effective dose conversion coefficients for radiographic examinations of the pediatric skull estimated by Monte Carlo methods

The objective of the present work was to provide precise effective and organ dose data for radiographic examinations of the skull performed on pediatric patients. To accomplish this, the MCNP4C2 transport code was utilized and 18 mathematical anthropomorphic phantoms, representing ages from a newborn child to a 17-year-old adolescent, were developed. Three common projections, anterior–posterior, posterior–anterior and lateral, were considered. The results consist of effective and organ radiation doses normalized to the entrance surface dose. Normalized data are presented for a wide range of peak kilovoltages and beam filtration values so that doses for any X-ray unit can be calculated. Both organ and effective dose values showed an inverse correlation with age. Good agreement was observed between the normalized effective doses produced in this study and values derived from calculations based on the National Radiological Protection Board coefficients for specific mathematical phantoms representing 1-, 5-, 10- and 15-year-old children. In the present work, dose data for nine mathematical phantoms representing 0-, 1-, 2-, 3-, 4-, 5-, 6-, 9- and 14-year-old pediatric patients were provided for estimation of organ and effective doses delivered to pediatric patients from radiographic examinations of the skull.     

Analysis of effective and organ dose estimation in CT when using mA modulation: A single scanner pilot study

IntroductionEffective dose (ED) estimation in CT examinations can be obtained by combining dose length product (DLP) with published ED per DLP coefficients or performed using software. These methods do not account for tube current (mA) modulation which is influenced by patient size. The aim of the work was to compare different methods of organ and ED estimation to measured values when using mA modulation in CT chest, abdomen and pelvis examinations.MethodOrgan doses from CT of the chest, abdomen and pelvis were measured using digital dosimeters and a dosimetry phantom. ED was calculated. Six methods of estimating ED accounting for mA modulation were performed using ImPACT CTDosimetry and Dose Length Product to ED coefficients. Corrections for the phantom mass were applied resulting in 12 estimation methods. Estimated organ doses from ImPACT CTDosimtery were compared to measured values.ResultsCalculated EDs were; chest 12.35 mSv (±1.48 mSv); abdomen 8.74 mSv (±1.36 mSv) and pelvis 4.68 mSv (±0.75 mSv). There was over estimation in all three anatomical regions. Correcting for phantom mass improved agreement between measured and estimated ED. Organ doses showed overestimation of dose inside the scan range and underestimation outside the scan range.ConclusionReasonable estimation of effective dose for CT of the chest and abdomen can be obtained using ImPACT CTDosimetry software or k-coefficients. Further work is required to improve the accuracy of ED estimation from CT of the pelvis. Accuracy of organ dose estimation has been shown to depend on the inclusion or exclusion of the organ from the scan range.