Objective To understand the distribution of the average glandular dose(AGD) in mammography by investigating 1,828 exposure parameters of 8 mammography machines in three cities, by using random sampling. Methods A surv...Objective To understand the distribution of the average glandular dose(AGD) in mammography by investigating 1,828 exposure parameters of 8 mammography machines in three cities, by using random sampling. Methods A survey of 8 mammography machines in three different cities, sampled using stratified random sampling methods, was performed, and 1,828 mammography exposure parameters were recorded. Incident air kerma(k) was measured by Quality-Assurance(QA) dosimeters, and AGD was calculated by series conversion coefficients based on a 3D detailed Monte Carlo breast model, published by Wang et al. Results The distribution of compressed breast thickness(CBT) fitted a normal distribution, while that of AGD fitted a skewed distribution. The mean value of CBT in a medio-lateral oblique(MLO) view was about 5.6% higher than that in the craniocaudal(CC) view, with significant statistical difference; mean value of AGD and CBT in the sample was 1.3 mGy and 4.6 cm, respectively. The AGD trended upward with increasing CBT, similar to the results of other researches. Conclusion The mean AGD and CBT levels in our study for mammography practice in China were 1.3 mGy and 4.6 cm, respectively. AGD is influenced by manufacturer-specific variation as machine response to CBT changes and target/filter combination. The present study can provide evidence for establishing a diagnostic reference level in China.展开更多
A survey of 420 exposures of mammography was performed with the parameters recorded. Entrance skin air kerma （ESAK） was measured and the mean glandular dose （MGD） was calculated according to the Dance＇s formula. ...A survey of 420 exposures of mammography was performed with the parameters recorded. Entrance skin air kerma （ESAK） was measured and the mean glandular dose （MGD） was calculated according to the Dance＇s formula. Correlation analysis showed that several factors could affect the MGD level. Mann-whitney test and Non-parametric ANOVA analyses were used to compare the MGD level grouped by view type and radiographic systems, No significant difference was found in MGD between the craniocaudal （CC） group and the mediolateral oblique （MLO） group. The MGD level was higher in the CR group than in the other two groups. MGD was positively correlated with the compressed breast thickness （CBT）. MGD varied with the half value layer （HVL） and increased first then decreased, The mean MGD level in China is about 1.6 mGy and is lower than the guidance level in the International Basic Safety Standards （IBSS）.展开更多
针对电-气-热综合能源系统(integrated energy system,IES),建立了非高斯测量噪声下的量测-状态方程。考虑耦合元件边界条件,将其既作为等式约束又作为虚拟量测方程,基于极大似然鲁棒状态估计方法,提出了一种考虑边界等式约束的电-气-热...针对电-气-热综合能源系统(integrated energy system,IES),建立了非高斯测量噪声下的量测-状态方程。考虑耦合元件边界条件,将其既作为等式约束又作为虚拟量测方程,基于极大似然鲁棒状态估计方法,提出了一种考虑边界等式约束的电-气-热IES鲁棒状态估计方法。在高斯和非高斯噪声下,进行仿真验证。仿真结果证明:所提方法可为IES在线分析和优化调度提供准确的全局状态感知。展开更多
基金supported by the Jiangsu Province’s Outstanding Medical Academic Leader Program [CXTDA2017029]Jiangsu Province's Key Medical Discipline of Epidemiology [ZDXK A 2016008]+1 种基金Science and education strong industry engineering youth talent project [JKRC2016014]Jiangsu Provincial preventive medicine research project [Y2018082]
文摘Objective To understand the distribution of the average glandular dose(AGD) in mammography by investigating 1,828 exposure parameters of 8 mammography machines in three cities, by using random sampling. Methods A survey of 8 mammography machines in three different cities, sampled using stratified random sampling methods, was performed, and 1,828 mammography exposure parameters were recorded. Incident air kerma(k) was measured by Quality-Assurance(QA) dosimeters, and AGD was calculated by series conversion coefficients based on a 3D detailed Monte Carlo breast model, published by Wang et al. Results The distribution of compressed breast thickness(CBT) fitted a normal distribution, while that of AGD fitted a skewed distribution. The mean value of CBT in a medio-lateral oblique(MLO) view was about 5.6% higher than that in the craniocaudal(CC) view, with significant statistical difference; mean value of AGD and CBT in the sample was 1.3 mGy and 4.6 cm, respectively. The AGD trended upward with increasing CBT, similar to the results of other researches. Conclusion The mean AGD and CBT levels in our study for mammography practice in China were 1.3 mGy and 4.6 cm, respectively. AGD is influenced by manufacturer-specific variation as machine response to CBT changes and target/filter combination. The present study can provide evidence for establishing a diagnostic reference level in China.
基金supported in part by Science and Education Health Project of Jiangsu Province during the Twelfth-Five Plan Period(No.ZX201109)National Health Industry Research and Special Project(No.201002009)
文摘A survey of 420 exposures of mammography was performed with the parameters recorded. Entrance skin air kerma （ESAK） was measured and the mean glandular dose （MGD） was calculated according to the Dance＇s formula. Correlation analysis showed that several factors could affect the MGD level. Mann-whitney test and Non-parametric ANOVA analyses were used to compare the MGD level grouped by view type and radiographic systems, No significant difference was found in MGD between the craniocaudal （CC） group and the mediolateral oblique （MLO） group. The MGD level was higher in the CR group than in the other two groups. MGD was positively correlated with the compressed breast thickness （CBT）. MGD varied with the half value layer （HVL） and increased first then decreased, The mean MGD level in China is about 1.6 mGy and is lower than the guidance level in the International Basic Safety Standards （IBSS）.
文摘针对电-气-热综合能源系统(integrated energy system,IES),建立了非高斯测量噪声下的量测-状态方程。考虑耦合元件边界条件,将其既作为等式约束又作为虚拟量测方程,基于极大似然鲁棒状态估计方法,提出了一种考虑边界等式约束的电-气-热IES鲁棒状态估计方法。在高斯和非高斯噪声下,进行仿真验证。仿真结果证明:所提方法可为IES在线分析和优化调度提供准确的全局状态感知。
