期刊文献+
共找到648篇文章
< 1 2 33 >
每页显示 20 50 100
Binary Phase Shaping and SHG Contrast Ratios
1
作者 Tingyao Xiong 《Journal of Applied Mathematics and Physics》 2024年第8期3026-3035,共10页
Finding binary sequences with Large SHG ratios is very important in the field of ultrafast science, biomedical optics, high-resolution microscopy and label-free imaging. In this paper, we have demonstrated the relatio... Finding binary sequences with Large SHG ratios is very important in the field of ultrafast science, biomedical optics, high-resolution microscopy and label-free imaging. In this paper, we have demonstrated the relation between the SHG contrast ratio and the traditional Merit Factor values. And in the light from known results in Merit Factor Problems, we have shown that Legendre Sequences or Jacobi Sequences, are still the best candidates to obtain binary sequences with large SHG contrast ratios. The authors also discussed the SHG behaviors on some sequences obtained from cyclotomic classes over the finite field GF (2l) . 展开更多
关键词 Binary Phase Shaping Binary Sequences SHG contrast ratio Merit Factor
下载PDF
Colorless to black switching with high contrast ratio via the electrochemical process of a hybrid organic-inorganic perovskite 被引量:1
2
作者 Ming Xu Jianmin Gu +5 位作者 Zixun Fang Yu Li Xing Wang Xiaoyu Zhao Tifeng Jiao Wei Wang 《Carbon Energy》 SCIE EI CAS CSCD 2023年第11期90-100,共11页
Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy.However,it still remains a challenge owing to the t... Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy.However,it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states.Herein,we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr_(3),which shows a high integrated contrast ratio of up to 73%from 400 to 800 nm.The perovskite solution can be used as the active layer to assemble the device,showing superior transmittance over the entire visible region in neutral states.By applying an appropriate voltage,the device undergoes reversible switching between colorless and black,which is attributed to the formation of lead and Br_(2)in the redox reaction induced by the electron transfer process in MAPbBr_(3).In addition,the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage.These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices. 展开更多
关键词 colorless to black switching electrochemical process high integrated contrast ratio hybrid organic-inorganic perovskite switchable devices
下载PDF
Clinical Value of Dual-energy CT in Detection of Pancreatic Adenocarcinoma: Investigation of the Best Pancreatic Tumor Contrast to Noise Ratio 被引量:2
3
作者 Yong-lan He Da-ming Zhang +1 位作者 Hua-dan Xue Zheng-yu Jin 《Chinese Medical Sciences Journal》 CAS CSCD 2012年第4期207-212,共6页
Objective To quantitatively compare and determine the best pancreatic tumor contrast to noise ratio (CNR) in different dual-energy derived datasets. Methods In this retrospective, single center study, 16 patients (9 m... Objective To quantitatively compare and determine the best pancreatic tumor contrast to noise ratio (CNR) in different dual-energy derived datasets. Methods In this retrospective, single center study, 16 patients (9 male, 7 female, average age 59.4±13.2 years) with pathologically diagnosed pancreatic cancer were enrolled. All patients received an abdominal scan using a dual source CT scanner 7 to 31 days before biopsy or surgery. After injection of iodine contrast agent, arterial and pancreatic parenchyma phase were scanned consequently, using a dual-energy scan mode (100 kVp/230 mAs and Sn 140 kVp/178 mAs) in the pancreatic parenchyma phase. A series of derived dual-energy datasets were evaluated including non-liner blending (non-linear blending width 0-500 HU; blending center -500 to 500 HU), mono-energetic (40-190 keV), 100 kVp and 140 kVp. On each datasets, mean CT values of the pancreatic parenchyma and tumor, as well as standard deviation CT values of subcutaneous fat and psoas muscle were measured. Regions of interest of cutaneous fat and major psoas muscle of 100 kVp and 140 kVp images were calculated. Best CNR of subcutaneous fat (CNR F ) and CNR of the major psoas muscle (CNR M ) of non-liner blending and mono-energetic datasets were calculated with the optimal mono-energetic keV setting and the optimal blending center/width setting for the best CNR. One Way ANOVA test was used for comparison of best CNR between different dual-energy derived datasets. Results The best CNR F (4.48±1.29) was obtained from the non-liner blending datasets at blending center -16.6±103.9 HU and blending width 12.3±10.6 HU. The best CNR F (3.28±0.97) was obtained from the mono-energetic datasets at 73.3±4.3 keV. CNR F in the 100 kVp and 140 kVp were 3.02±0.91 and 1.56±0.56 respectively. Using fat as the noise background, all of these images series showed significant differences (P<0.01) except best CNR F of mono-energetic image sets vs. CNR F of 100 kVp image (P=0.460). Similar results were found using muscle as the noise background (mono-energetic image vs. 100 kVp image: P=0.246; mono-energetic image vs. non-liner blending image: P=0.044; others: P<0.01). Conclusion Compared with mono-energetic datasets and low kVp datasets, non-linear blending image at automatically chosen blending width/window provides better tumor to the pancreas CNR, which might be beneficial for better detection of pancreatic tumors. 展开更多
关键词 pancreatic adenocarcinoma DUAL-ENERGY contrast to noise ratio non-linear blending
下载PDF
Relationship of inflammatory indices with left atrial appendage thrombus or spontaneous echo contrast in patients with atrial fibrillation
4
作者 Zhao Wang Bin-Hao Wang +3 位作者 Xiao-Lei Yang Yun-Long Xia Sheng-Min Zhang Ying Che 《World Journal of Clinical Cases》 SCIE 2024年第21期4550-4557,共8页
BACKGROUND Inflammatory indices derived from complete blood tests have been reported to be associated with poor outcomes in patients with atrial fibrillation(AF).The data about the relationship between inflammatory in... BACKGROUND Inflammatory indices derived from complete blood tests have been reported to be associated with poor outcomes in patients with atrial fibrillation(AF).The data about the relationship between inflammatory indices and left atrial appendage thrombus(LAAT)or dense spontaneous echo contrast(SEC)are limited.AIM To explore the value of inflammatory indices for predicting the presence of LAAT or dense SEC in nonvalvular AF patients.METHODS A total of 406 patients with nonvalvular AF who underwent transesophageal echocardiography were included and divided into two groups based on the presence(study group)or absence(control group)of LAAT or dense SEC.Inflammatory indices,including the neutrophil-to-lymphocyte ratio(NLR),platelet–tolymphocyte ratio(PLR),and lymphocyte-to-monocyte ratio(LMR),were calculated from complete blood analysis.The associations of inflammatory indices RESULTS LAAT and dense SEC were detected in 11(2.7%)and 42(10.3%)patients,respectively.The PLR only showed an association with LAAT/dense SEC in the univariate model.Elevated NLR(odds ratio[OR]=1.48,95%confidence interval[CI]:1.11-1.98,P=0.007)and reduced LMR(OR=0.59,95%CI:0.41-0.83,P=0.003)were found to be independent risk factors for the presence of LAAT/dense SEC.The areas under the NLR and LMR curves for predicting LAAT/dense SEC were 0.73(95%CI:0.66-0.80,P<0.001)and 0.73(95%CI:0.65-0.81,P<0.001),respectively,while the cutoff values were 2.8(sensitivity:69.8%;specificity:64.0%)and 2.4(sensitivity:71.7%;specificity:60.6%),respectively.CONCLUSION Increased NLR and decreased LMR may predict LAAT/dense SEC in patients with nonvalvular AF. 展开更多
关键词 Nonvalvular atrial fibrillation Left atrial appendage thrombus Spontaneous echo contrast Neutrophil–lymphocyte ratio Lymphocyte–monocyte ratio
下载PDF
Spectral-Phase-Modulated Cross-Polarized Wave for Chirped Pulse Amplifier with High Contrast Ratio
5
作者 Shuang Qin Zhao-Hua Wang +3 位作者 Shuai-Shuai Yang Zhong-Wei Shen Quan-Li Dong Zhi-Yi Wei 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第2期43-46,共4页
We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by Well- eompressed spectral-phase fully-compensated fundamental laser lmlses, the filter stretches the pulse bandwi... We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by Well- eompressed spectral-phase fully-compensated fundamental laser lmlses, the filter stretches the pulse bandwidth from 35 nm to 7Ohm with a conversion efficeiency of 20%. 展开更多
关键词 Spectral-Phase-Modulated cross-Polarized Wave for Chirped Pulse Amplifier with High contrast ratio FTL
下载PDF
CHF患者CRP/Alb、PDGF、BUN/Cr水平变化及对预后的评估价值
6
作者 宋鑫 先本婧 刘峥嵘 《河北医药》 CAS 2024年第1期34-38,共5页
目的 探讨慢性心力衰竭(CHF)患者C-反应蛋白与白蛋白比值(CRP/Alb)、血小板源性生长因子(PDGF)联合血尿素氮与肌酐比值(BUN/Cr)水平变化,并分析各指标预测心血管死亡和全因死亡的效能。方法 选取2020年1月至2022年3月收治的109例CHF患者... 目的 探讨慢性心力衰竭(CHF)患者C-反应蛋白与白蛋白比值(CRP/Alb)、血小板源性生长因子(PDGF)联合血尿素氮与肌酐比值(BUN/Cr)水平变化,并分析各指标预测心血管死亡和全因死亡的效能。方法 选取2020年1月至2022年3月收治的109例CHF患者,根据1年内心血管死亡和全因死亡情况分为死亡组(26例)和存活组(83例)。比较2组社会人口学资料和临床特征[美国纽约心脏病学会心功能分级(NYHA)、左心室射血分数、左心室舒张末期内径、左心室收缩末期内径、N-末端脑钠肽前体(NT-proBNP)、临床用药]、CRP/Alb、PDGF、BUN/Cr水平,分析CRP/Alb、PDGF、BUN/Cr水平的相关性,采用Cox回归分析CHF患者心血管死亡和全因死亡的相关影响因素,采用受试者工作特征曲线(ROC)分析预测价值,采用卡普兰-迈耶曲线(K-M)生存曲线分析不同CRP/Alb、PDGF、BUN/Cr水平患者的生存率。结果 死亡组NYHA心功能分级、左心室舒张末期内径、左心室收缩末期内径、NT-proBNP高于存活组,左心室射血分数低于存活组(P<0.05);死亡组CRP/Alb、PDGF、BUN/Cr高于存活组(P<0.05);CHF患者CRP/Alb与PDGF、BUN/Cr呈正相关,PDGF与BUN/Cr呈正相关(P<0.05);在校正了NYHA心功能分级等混杂因素后,CRP/Alb、PDGF、BUN/Cr仍是CHF患者心血管死亡和全因死亡的相关影响因素(P<0.05);CRP/Alb、PDGF、BUN/Cr预测心血管死亡和全因死亡的ROC下面积(AUC)分别为0.712、0.801、0.738,三者联合时的AUC为0.911(P<0.05);CRP/Alb、PDGF、BUN/Cr高水平患者生存率低于低水平患者(P<0.05)。结论 CRP/Alb、PDGF、BUN/Cr与CHF患者心血管死亡和全因死亡有关,联合检测可作为预测患者病情转归的一个方案,为临床评估预后、治疗等提供参考依据。 展开更多
关键词 crP/Alb PDGF BUN/cr 慢性心力衰竭 心血管死亡 全因死亡
下载PDF
化学还原-生物刺激对高质量比Cr(Ⅵ)污染土壤治理及稳定化 被引量:1
7
作者 吴卿 莫文君 +3 位作者 刘洁琼 彭森 李倩男 万芮含 《安全与环境学报》 CAS CSCD 北大核心 2023年第9期3346-3354,共9页
为提高Cr(Ⅵ)污染土壤治理后的稳定性,采用化学还原剂联合乙酸钠生物刺激对高质量比Cr(Ⅵ)污染土壤进行治理和稳定化。通过测定Cr(Ⅵ)质量比、Cr形态及含量并结合XRD分析,同时对生物刺激过程中Cr(Ⅵ)污染土壤的细菌多样性变化进行监测,... 为提高Cr(Ⅵ)污染土壤治理后的稳定性,采用化学还原剂联合乙酸钠生物刺激对高质量比Cr(Ⅵ)污染土壤进行治理和稳定化。通过测定Cr(Ⅵ)质量比、Cr形态及含量并结合XRD分析,同时对生物刺激过程中Cr(Ⅵ)污染土壤的细菌多样性变化进行监测,对比多硫化钙(Calcium polysulfide,CPS)、硫酸亚铁(FeSO4)、零价铁3种化学还原剂以及乙酸钠用量对高质量比Cr(Ⅵ)污染土壤的治理能力及稳定化效果。结果表明:质量分数为10%的FeSO4与质量比为7 g/kg的乙酸钠联用,在生物刺激50 d时对高质量比Cr(Ⅵ)的去除及稳定化效果最佳,还原率为93.58%,且能够将毒性较大的生物有效态铬全部转化为其他稳定形态的铬。XRD结果表明,两种方法联用后土壤中Cr主要以Cr(Ⅲ)的形式存在。生物刺激过程中土壤细菌群落物种分布变化明显,生物刺激50 d时,富集的细菌类群最多。 展开更多
关键词 环境工程学 高质量比cr(Ⅵ)污染土壤 化学还原 生物刺激 细菌多样性
下载PDF
Optimization of Cr/Mo molar ratio in FeCoCrMoCBY alloys for high corrosion resistance 被引量:3
8
作者 Cheng-jie WANG Qing-jun CHEN Huai-xiao XIA 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2017年第12期2663-2672,共10页
The corrosion behavior of bulk metallic glasses(BMGs)(Fe41Co7Cr15Mo14C15B6Y2)100-xCrx(x=0,4,8,12,molar fraction,%)was investigated in1mol/L HCl aqueous solution with electrochemical tests.The electrochemical measureme... The corrosion behavior of bulk metallic glasses(BMGs)(Fe41Co7Cr15Mo14C15B6Y2)100-xCrx(x=0,4,8,12,molar fraction,%)was investigated in1mol/L HCl aqueous solution with electrochemical tests.The electrochemical measurements demonstrate that the passive current density of Fe-based amorphous alloy is reduced by about one order of magnitude,and meanwhile,the stability of passive film can be guaranteed by the Cr/Mo molar ratio.The Mott–Schottky(M–S)curves show that the passive film is the densest when the molar ratio of Cr/Mo is between1.37and1.69.X-ray photoelectron spectroscopy(XPS)analysis was performed to clarify chemical states of elements in the passive films.The results show that the corrosion resistance of the alloy is related to the molar ratio of Cr/Mo.The stability of passive film is determined by the synergistic action of Cr and Mo elements.The main component of the passive film is Cr3+oxide.When the potential is greater than0.5V(vs SCE),Mo6+ions play an important role in keeping the stability of the passive film.The appropriate molar ratio of Cr/Mo can reduce the dissolution rate of the passive film. 展开更多
关键词 bulk metallic glasses corrosion resistance passive film electrochemical measurement cr/Mo molar ratio
下载PDF
UACR联合血清KIM-1、NGAL对冠心病病人术后并发造影剂肾病的预测分析 被引量:2
9
作者 祁兴敏 安惠旒 +4 位作者 王瑞 曹炜红 焦霞 王世杰 于改革 《蚌埠医学院学报》 CAS 2023年第2期178-181,共4页
目的:探讨尿微量白蛋白/尿肌酐比值水平(urine micro-albumin/urinary creatinine ratio,UACR)联合血清肾损伤分子-1(kidney injury molecule-1,KIM-1)、中性粒细胞明胶酶相关脂质运载蛋白(neutrophil gelatinase-associated lipocalin,... 目的:探讨尿微量白蛋白/尿肌酐比值水平(urine micro-albumin/urinary creatinine ratio,UACR)联合血清肾损伤分子-1(kidney injury molecule-1,KIM-1)、中性粒细胞明胶酶相关脂质运载蛋白(neutrophil gelatinase-associated lipocalin,NGAL)对冠心病病人术后并发造影剂肾病(contrast-induced nephropathy,CIN)的评估价值。方法:选取162例冠心病病人,均行冠状动脉造影、经皮冠状动脉介入术,根据术后是否发生CIN分为CIN组(22例)、非CIN组(140例)。比较2组病人临床基线资料以及术后24 h的UACR、血清KIM-1、NGAL水平,采用多因素logistic回归分析CIN发生的危险因素,采用受试者工作特征曲线(ROC曲线)分析UACR、KIM-1、NGAL预测CIN的诊断价值。结果:CIN病人术后24 h的NGAL、血清KIM-1、UACR水平以及术前尿肌酐均高于非CIN组,而术前肾小球滤过率低于对照组,差异有统计学意义(P<0.05~P<0.01)。多因素logistic回归分析显示,UACR、KIM-1、NGAL升高均是CIN发生的危险因素(P<0.01)。ROC曲线分析显示,NGAL、KIM-1、UACR以及联合诊断预测CIN的曲线下面积分别为0.826、0.801、0.790、0.886,联合诊断的曲线下面积明显高于单独诊断,差异有统计学意义(P<0.05)。结论:UACR以及血清KIM-1、NGAL是冠心病病人术后发生CIN的独立危险因素,发生CIN的高风险病人各指标均处于较高水平,三种指标联合检测可提高CIN的预测价值。 展开更多
关键词 造影剂肾病 尿微量白蛋白/尿肌酐比值水平 肾损伤分子-1 中性粒细胞明胶酶相关脂质运载蛋白
下载PDF
基于长裂纹扩展阈值的渗碳Cr-Ni合金钢超高周疲劳极限评估
10
作者 杨溥 刘兵 +3 位作者 邓海龙 陈雨 孔建行 于欢 《制造技术与机床》 北大核心 2023年第10期98-103,共6页
文章旨在构建渗碳Cr-Ni合金钢的超高周疲劳极限预测模型。在两种应力比下对渗碳Cr-Ni合金钢开展超高周疲劳试验,结果表明,渗碳Cr-Ni合金钢的S-N特性呈现持续下降的趋势。通过扫描电镜对断口表面裂纹形貌的观测,当疲劳寿命低于5×10^... 文章旨在构建渗碳Cr-Ni合金钢的超高周疲劳极限预测模型。在两种应力比下对渗碳Cr-Ni合金钢开展超高周疲劳试验,结果表明,渗碳Cr-Ni合金钢的S-N特性呈现持续下降的趋势。通过扫描电镜对断口表面裂纹形貌的观测,当疲劳寿命低于5×10^(5)周次时,表面失效是疲劳试样主要失效形式,当寿命高于1×10^(6)周次时,内部夹杂-FGA-鱼眼诱发失效成为渗碳Cr-Ni合金钢的主要失效方式。利用裂纹扩展阈值对FGA尺寸进行了评估,结合El-Haddad模型,构建了基于长裂纹扩展应力强度因子阈值的疲劳极限预测模型。与他人模型预测的疲劳极限对比,得出构建的阈值应力模型预测的疲劳极限误差最小,预测结果更保守。 展开更多
关键词 渗碳cr-Ni合金钢 变应力比 S-N曲线 应力强度因子 疲劳极限预测
下载PDF
Applications of Compliance to Cost Ratio (C-CR) Analysis in the Determination of Optimum Mix of Insulating Bricks in Masonry
11
作者 Davies Oladayo Folorunso Abayomi Adewale Akinwande 《Journal of Minerals and Materials Characterization and Engineering》 2021年第2期134-147,共14页
The scarcity of housing increases as population continues to rise all over the world. Despite government efforts at providing houses, yearly demand keeps on exceeding available houses and hence the hike in rent, the c... The scarcity of housing increases as population continues to rise all over the world. Despite government efforts at providing houses, yearly demand keeps on exceeding available houses and hence the hike in rent, the cost of erecting houses and the cost of building materials. This ultimately calls for a decisive solution. This study therefore applied compliance to cost ratio (C-CR) analysis in evaluating the optimum properties of fired ceramic bricks. The optimum mix proportions of waste glass (WG) and wood saw dust (WSD) in fired bricks, that will be suitable for housing constructions were hence determined. Fired clay brick samples which contained varied proportions of WG and WSD were examined for physical, mechanical and thermal properties in line with standard procedures. The results were compared with existing standards and property evaluation index, compliance level and C-CR were applied in analyzing the results obtained. It was observed that with increasing WG content, compliance level increased. Also, cost ratio and experimental cost of each brick sample trended upward. Sample with mix proportion;20 wt% WG, 5 wt% WSD and 75 wt% clay had compliance level of 94% and C-CR index of 7.81, hence chosen as optimum mix proportion for masonry bricks. 展开更多
关键词 Properties Evaluation HOUSING Fired Clay Bricks Compliance to Cost ratio (C-cr) and Masonry
下载PDF
自主研发高分辨盆腔专用线圈在3.0 T磁共振设备成像价值的评估
12
作者 王晓 郑福玲 +8 位作者 陆晓平 李娟 张鹏 刘梦超 金川 张宏宇 王天娇 王沄 薛华丹 《磁共振成像》 CAS CSCD 北大核心 2024年第1期158-162,178,共6页
目的探讨自主研发的16通道高分辨盆腔专用线圈(16C)在3.0 T盆腔MRI中的应用价值。材料和方法前瞻性招募35例行盆腔MRI的患者,分别用16C线圈和32通道的体部线圈(32C)采集相同的轴位和矢状位T2WI序列。比较相同序列图像中第三骶椎、子宫... 目的探讨自主研发的16通道高分辨盆腔专用线圈(16C)在3.0 T盆腔MRI中的应用价值。材料和方法前瞻性招募35例行盆腔MRI的患者,分别用16C线圈和32通道的体部线圈(32C)采集相同的轴位和矢状位T2WI序列。比较相同序列图像中第三骶椎、子宫肌层、前列腺外周带、直肠壁和闭孔内肌的信噪比(signal to noise ratio,SNR)及对比噪声比(contrast to noise ratio,CNR)。由两位诊断医师各自对两组图像质量和直肠轴位图像直肠壁分层结构的显示度进行主观评分。结果两组线圈相同序列的T2WI矢状位第三骶椎、子宫肌层、前列腺外周带和轴位闭孔内肌的SNR差异具有统计学意义(P<0.05),矢状位第三骶椎、子宫肌层和轴位直肠壁对肌肉的CNR差异具有统计学意义(P<0.05),16C组高于32C组。两组线圈相同序列的T2WI图像质量主观评价差异具有统计学意义(P<0.05),16C组图像质量更优。在轴位T2WI直肠壁分层结构的显示度评价方面两组图像差异具有统计学意义(P<0.05),16C组更优。结论16C线圈在3.0 T磁共振设备上成像质量更好,更有利于盆腔疾病的诊断。 展开更多
关键词 磁共振成像 线圈 信噪比 对比噪声比 图像质量
下载PDF
基于RCC-M规范要求的CR技术等价性分析
13
作者 张亮 谭素平 +1 位作者 臧功志 付凯中 《集成电路应用》 2023年第2期61-63,共3页
阐述RCC-M规范要求,分析了胶片照相技术中图像质量对比度、不清晰度和颗粒度的要求,等价得出数字射线技术图像质量的技术要求。通过典型厚度平板试块和自然缺陷管道试块的透照试验,验证CR技术与胶片照相技术的图像质量差异性,得出在一... 阐述RCC-M规范要求,分析了胶片照相技术中图像质量对比度、不清晰度和颗粒度的要求,等价得出数字射线技术图像质量的技术要求。通过典型厚度平板试块和自然缺陷管道试块的透照试验,验证CR技术与胶片照相技术的图像质量差异性,得出在一定透照厚度范围内CR技术能够与胶片照相技术达到相同的检测能力。 展开更多
关键词 RCC-M规范 cr技术 信噪比 图像不清晰度
下载PDF
三维多回波聚合梯度回波序列在腰骶丛成像中的初步应用
14
作者 李运运 彭传勇 +2 位作者 吴宗山 徐启兰 陈琪 《分子影像学杂志》 2024年第4期403-406,共4页
目的 探讨3D多回波聚合梯度回波序列(3D GEMEC)在腰骶丛神经成像中的应用价值。方法 回顾性分析2022年8~9月六安市人民医院以腰腿疼为主诉的32例住院患者的影像学资料,男15例,女17例,年龄28~78(60.1±15.8)岁。在不同1.5T平台上分... 目的 探讨3D多回波聚合梯度回波序列(3D GEMEC)在腰骶丛神经成像中的应用价值。方法 回顾性分析2022年8~9月六安市人民医院以腰腿疼为主诉的32例住院患者的影像学资料,男15例,女17例,年龄28~78(60.1±15.8)岁。在不同1.5T平台上分别完成腰骶丛3D GEMEC序列和三维T2加权快速梯度回波(3D T2 FFE)序列,比较两种序列腰骶丛神经的信噪比、对比噪声比和主观显示效果。结果 3D GEMEC序列腰骶丛神经的信噪比、对比噪声比以及主观显示效果与3D T2 FFE序列的差异均无统计学意义(P=0.250、0.146、0.083)。结论 3D GEMEC序列可以清晰地显示腰骶丛神经的解剖结构并抑制背景信号,在腰骶丛神经病变的诊断方面具有一定的临床应用前景。 展开更多
关键词 腰骶丛神经 磁共振成像技术 3D多回波聚合梯度回波序列 信噪比 对比噪声比
下载PDF
磁共振AIR-魔毯线圈在胸椎结核扫描中的应用价值
15
作者 徐冬 王玉群 +1 位作者 孙萌萌 侯代伦 《医学影像学杂志》 2024年第6期118-120,共3页
目的探讨联合应用AIR-魔毯线圈磁共振成像(MRI)对胸椎结核扫描图像信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和脂肪抑制成像效果的价值。方法选取我院80例经手术病理证实为胸椎结核患者,按1:1随机... 目的探讨联合应用AIR-魔毯线圈磁共振成像(MRI)对胸椎结核扫描图像信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和脂肪抑制成像效果的价值。方法选取我院80例经手术病理证实为胸椎结核患者,按1:1随机分为两组,应用常规线圈(脊柱相控阵线圈,头颈联合线圈)、常规线圈联合AIR魔毯线圈对两组患者分别进行扫描。扫描序列包括胸椎矢状位T_(2)WI,T_(1)WI,T_(2)FLEX,进一步测量、比较SNR,CNR及脂肪抑制效果,分析MRI多序列诊断胸腰椎结核的准确率、特异度和灵敏度。结果常规线圈联合AIR-魔毯线圈扫描组,胸椎矢状位图像的SNR、CNR及压脂效果优于常规线圈组。结论联合应用AIR-魔毯线圈的图像SNR、CNR得到提高,脂肪抑制效果稳定良好。 展开更多
关键词 胸椎结核 磁共振成像 AIR-魔毯线圈 信噪比 对比噪声比
下载PDF
低对比剂摄入量能谱肺动脉成像虚拟平扫代替胸部平扫的可行性
16
作者 方鑫 刘义军 +3 位作者 王旭 李贝贝 姜健 张竞颐 《中国医学影像学杂志》 CSCD 北大核心 2024年第9期956-960,共5页
目的 探讨能谱CT虚拟平扫技术在肺动脉成像(CTPA)中代替胸部平扫降低患者辐射剂量的可行性。资料与方法 前瞻性收集2022年2—11月于大连医科大学附属第一医院行CTPA检查的56例患者,均接受常规胸部平扫及能谱CTPA增强扫描。分别测量胸部... 目的 探讨能谱CT虚拟平扫技术在肺动脉成像(CTPA)中代替胸部平扫降低患者辐射剂量的可行性。资料与方法 前瞻性收集2022年2—11月于大连医科大学附属第一医院行CTPA检查的56例患者,均接受常规胸部平扫及能谱CTPA增强扫描。分别测量胸部平扫和虚拟平扫图像上胸主动脉、肺动脉主干、竖脊肌及肺尖层面、气管隆嵴层面、肺底层面的肺实质CT值及噪声,并计算胸主动脉、肺动脉信噪比、对比噪声比。对两组图像质量及碘残留进行主观评价,并检验主观评分的一致性。记录患者剂量长度乘积、CT容积剂量指数及对比剂用量。比较胸部平扫和虚拟平扫图像各感兴趣区CT值、信噪比、对比噪声比、辐射剂量和主观评分。结果 2名医师的主观评分一致性较好(Kappa=0.984~0.992,P<0.05),胸部平扫、虚拟平扫图像主观评分分别为(4.75±0.65)分、(4.65±0.49)分,差异无统计学意义(t=0.630,P=0.437)。胸部平扫与虚拟平扫图像胸主动脉、肺动脉、各区域肺组织CT值差异无统计学意义(P>0.05);肺动脉及胸主动脉信噪比、对比噪声比差异无统计学意义(P>0.05)。用CTPA的虚拟平扫代替常规胸部平扫,患者辐射剂量由(7.27±1.74)mSv减少至(3.26±0.84)mSv,减少约55%。结论 CTPA虚拟平扫可代替胸部常规CT平扫用于肺部疾病筛查,大幅降低患者的辐射剂量。 展开更多
关键词 肺动脉成像 体层摄影术 X线计算机 造影剂 噪声 信噪比 辐射剂量 胸部
下载PDF
杨氏干涉实验中双孔的振动对衬比度的影响
17
作者 骆素华 姜向前 《物理通报》 CAS 2024年第7期105-107,112,共4页
研究了杨氏干涉实验中双孔的振动对衬比度的影响.利用复振幅叠加方法给出了当两个孔做振动方向相反的简谐振动时一对双孔对任一场点、任意时刻的光强表达式,进而给出双孔做简谐振动时双孔的分布函数.利用分布函数得到干涉场的稳态分布,... 研究了杨氏干涉实验中双孔的振动对衬比度的影响.利用复振幅叠加方法给出了当两个孔做振动方向相反的简谐振动时一对双孔对任一场点、任意时刻的光强表达式,进而给出双孔做简谐振动时双孔的分布函数.利用分布函数得到干涉场的稳态分布,由光场的稳态分布得到衬比度,发现衬比度随位置呈一个振幅衰减的拉比振荡形式. 展开更多
关键词 杨氏干涉 衬比度 拉比振荡
下载PDF
不同对比剂流速对肝癌患者CT增强扫描图像的影响
18
作者 卢铮 《医疗装备》 2024年第12期13-15,19,共4页
目的 探讨不同对比剂流速对肝癌患者CT增强扫描图像的影响。方法 选取2019年1月至2022年12月于医院收治的156例肝癌患者为研究对象,根据随机数字表法分为试验组与对照组,每组78例。所有患者均行CT增强扫描,碘海醇注射液剂量为100 ml,试... 目的 探讨不同对比剂流速对肝癌患者CT增强扫描图像的影响。方法 选取2019年1月至2022年12月于医院收治的156例肝癌患者为研究对象,根据随机数字表法分为试验组与对照组,每组78例。所有患者均行CT增强扫描,碘海醇注射液剂量为100 ml,试验组对比剂流速为2.0~2.5 ml/s,对照组对比剂流速为3.5~4.0 ml/s,记录两组不良反应发生情况、影像学特征、辐射剂量与图像质量。结果 试验组不良反应发生率低于对照组(P <0.05);所有患者图像均能显示4~6级肝血管分支;两组图像质量评分比较,差异无统计学意义(P>0.05)。试验组图像信噪比和对比噪声比低于对照组(P<0.05);两组剂量长度乘积与有效剂量比较,差异无统计学意义(P>0.05)。两组动脉期、门脉期、平衡期的病灶检出率比较,差异无统计学意义(P>0.05)。结论 CT增强扫描中对比剂流速降低不会影响图像质量及病灶检出率,且不增加辐射剂量,但可降低不良反应发生率、图像信噪比和对比噪声比。 展开更多
关键词 CT增强扫描 对比剂流速 图像质量 不良反应 辐射剂量
下载PDF
中坝遗址地层的Cr/Cu值对干湿环境的指示意义 被引量:10
19
作者 李中轩 朱诚 +3 位作者 朱青 马春梅 张广胜 欧阳杰 《地理科学》 CSCD 北大核心 2008年第6期799-803,共5页
将中坝遗址5 ka以来连续沉积地层按文化序列分为12层,分别测量Rb、Sr和Cr、Cu含量,对比显示,Cr/Cu比值与Rb/Sr比值明显正相关。Cr与Rb的属性相似,Cr化学活性低,易于在粉砂质沉积物中富集;而Cu和Sr在成壤过程中容易迁移,在粘土质沉积层... 将中坝遗址5 ka以来连续沉积地层按文化序列分为12层,分别测量Rb、Sr和Cr、Cu含量,对比显示,Cr/Cu比值与Rb/Sr比值明显正相关。Cr与Rb的属性相似,Cr化学活性低,易于在粉砂质沉积物中富集;而Cu和Sr在成壤过程中容易迁移,在粘土质沉积层中含量较高。通过对Cr、Cu元素在表生环境下的化学性质、沉积地层的属性、微地貌特征、与泥炭腐殖化度古里雅冰芯氧同位素曲线等指标对比表明,Cr/Cu比值变化对环境干湿变化的指示具有普遍意义。 展开更多
关键词 中坝遗址 cr/Cu值 Rb/Sr值
下载PDF
基于图像形态学的焊缝区域提取与对比度提升技术
20
作者 刘欢 刘骁佳 +3 位作者 赵耀邦 王宁 罗志强 危荃 《中国材料进展》 CAS CSCD 北大核心 2024年第2期175-180,共6页
铝板焊接后可使用X射线进行焊缝内部缺陷检测,由于X射线成像存在噪声多、对比度低、焊缝区域边缘模糊、焊缝区域与背景区域灰度分布较为相似等问题,使用传统边缘检测方法效果欠佳。提出了一种自动提取焊缝区域并提高其对比度的方法,通... 铝板焊接后可使用X射线进行焊缝内部缺陷检测,由于X射线成像存在噪声多、对比度低、焊缝区域边缘模糊、焊缝区域与背景区域灰度分布较为相似等问题,使用传统边缘检测方法效果欠佳。提出了一种自动提取焊缝区域并提高其对比度的方法,通过去噪处理、边缘检测、形态学操作等步骤,最终确定焊缝区域位置,并对焊缝区域内像素值进行线性变换,提高了焊缝区域的对比度。实验结果表明,该方法针对大批量的铝板X射线图片,都能够自动提高焊缝区域的对比度,具有良好的鲁棒性和准确性。 展开更多
关键词 图像处理 X射线 焊缝区域 梯度 对比度
下载PDF
上一页 1 2 33 下一页 到第
使用帮助 返回顶部