目的探讨动态对比增强MRI(dynamic contrast-enhancement MRI,DCE-MRI)瘤周血管特征结合瘤内血流动力学参数在乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)4类肿瘤中的鉴别诊断价值。材料与方法回顾性分...目的探讨动态对比增强MRI(dynamic contrast-enhancement MRI,DCE-MRI)瘤周血管特征结合瘤内血流动力学参数在乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)4类肿瘤中的鉴别诊断价值。材料与方法回顾性分析2018年8月至2023年3月于大连医科大学附属第一医院行乳腺MRI检查为BI-RADS 4类且病理结果明确肿瘤的女性病例102例,其中良性组43例,恶性组59例。记录患者年龄、病灶最大径(dmax)、乳腺DCE-MRI基本影像学特征、瘤周血管特征及瘤内血流动力学参数值。通过单因素和多因素logistic回归分析比较两组间多参数的差异,利用受试者工作特征(receiver operating characteristic,ROC)曲线以及曲线下面积(area under the curve,AUC)分析瘤周血管特征指标与瘤内参数值联合应用对BI-RADS 4类乳腺良恶性两组肿瘤鉴别的诊断效能。应用DeLong检验对AUC进行比较。结果乳腺良性组和恶性组病例在年龄、dmax、背景实质强化(background parenchymal enhancement,BPE)、纤维腺体组织量(fibroglandular tissue,FGT)、瘤周相邻血管征(adjacent vascular sign,AVS)数目、瘤周血管最大径、患侧瘤周与健侧同一象限血管直径差值(△d)、瘤周血管出现期相以及瘤内容积转移常数(volume transfer constant,K^(trans))、速率常数(flux rate constant,K_(ep))、最大增强斜率(maximum slope of increase,MSI)和时间-信号强度曲线(time-signal intensity curve,TIC)类型的差异均具有统计学意义(P<0.05),而病变位置、信号增强率(signal enhancement ratio,SER)和血管外细胞外间隙容积比(volume fraction of extravascular extra vascular space,V_(e))差异无统计学意义(P>0.05)。通过多因素logistic回归分析结果显示,△d、dmax、MSI和K^(trans)为区分两组间的独立影响因素,其中优势比最大的是MSI值(AUC为0.923)。将瘤周血管特征△d分别与dmax、MSI和K^(trans)进行两者联合模型比较,以△d与MSI联合模型的诊断效能最高(AUC为0.933,敏感度和特异度分别为93.2%和83.7%),且△d联合MSI与△d联合K^(trans)比较的差异具有统计学意义(P=0.001);其他联合指标在两两比较时差异无统计学意义(P>0.05),联合模型高于单独MSI模型的诊断效能。结论瘤周血管特征指标(△d)联合瘤内半定量(MSI)血流动力学参数对评价BI-RADS 4类乳腺肿瘤具有较好的鉴别诊断价值。展开更多
The electric drive system characteristics of different projects for tracked vehicles are analyzed.For the two most typical projects,the parameters of power,torque and rotating speed and others of drive motor are figur...The electric drive system characteristics of different projects for tracked vehicles are analyzed.For the two most typical projects,the parameters of power,torque and rotating speed and others of drive motor are figured out under the condition of satisfying adequate steering performance of the tracked vehicles.General opinions on the two projects are brought forward and conclusions are drawn.展开更多
In this paper,we suggest an adaptive watermarking method to improve both transparence and robustness of quantization index modulation(QIM) scheme. Instead of a fixed quantization step-size,we apply a step-size adapted...In this paper,we suggest an adaptive watermarking method to improve both transparence and robustness of quantization index modulation(QIM) scheme. Instead of a fixed quantization step-size,we apply a step-size adapted to image content in each 8×8 block to make a balance of robust extraction and transparent embedding.The modified step-size is determined by contrast masking thresholds of Watson’s perceptual model.From a normalized crossed-correlation value between the original watermark and the detected watermark,we could observe that our method is robust to attacks of additive white Gaussian noise(AWGN),Salt and Pepper noise and Joint Photographic Experts Group(JPEG) compression than the original QIM.By taking into account the contrast insensitivity and visible thresholds of human visual system,the suggested improvement achieves a maximum embedding strength and an appropriate quantization step-size which is consistent with local values of a host signal.展开更多
文摘目的探讨动态对比增强MRI(dynamic contrast-enhancement MRI,DCE-MRI)瘤周血管特征结合瘤内血流动力学参数在乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)4类肿瘤中的鉴别诊断价值。材料与方法回顾性分析2018年8月至2023年3月于大连医科大学附属第一医院行乳腺MRI检查为BI-RADS 4类且病理结果明确肿瘤的女性病例102例,其中良性组43例,恶性组59例。记录患者年龄、病灶最大径(dmax)、乳腺DCE-MRI基本影像学特征、瘤周血管特征及瘤内血流动力学参数值。通过单因素和多因素logistic回归分析比较两组间多参数的差异,利用受试者工作特征(receiver operating characteristic,ROC)曲线以及曲线下面积(area under the curve,AUC)分析瘤周血管特征指标与瘤内参数值联合应用对BI-RADS 4类乳腺良恶性两组肿瘤鉴别的诊断效能。应用DeLong检验对AUC进行比较。结果乳腺良性组和恶性组病例在年龄、dmax、背景实质强化(background parenchymal enhancement,BPE)、纤维腺体组织量(fibroglandular tissue,FGT)、瘤周相邻血管征(adjacent vascular sign,AVS)数目、瘤周血管最大径、患侧瘤周与健侧同一象限血管直径差值(△d)、瘤周血管出现期相以及瘤内容积转移常数(volume transfer constant,K^(trans))、速率常数(flux rate constant,K_(ep))、最大增强斜率(maximum slope of increase,MSI)和时间-信号强度曲线(time-signal intensity curve,TIC)类型的差异均具有统计学意义(P<0.05),而病变位置、信号增强率(signal enhancement ratio,SER)和血管外细胞外间隙容积比(volume fraction of extravascular extra vascular space,V_(e))差异无统计学意义(P>0.05)。通过多因素logistic回归分析结果显示,△d、dmax、MSI和K^(trans)为区分两组间的独立影响因素,其中优势比最大的是MSI值(AUC为0.923)。将瘤周血管特征△d分别与dmax、MSI和K^(trans)进行两者联合模型比较,以△d与MSI联合模型的诊断效能最高(AUC为0.933,敏感度和特异度分别为93.2%和83.7%),且△d联合MSI与△d联合K^(trans)比较的差异具有统计学意义(P=0.001);其他联合指标在两两比较时差异无统计学意义(P>0.05),联合模型高于单独MSI模型的诊断效能。结论瘤周血管特征指标(△d)联合瘤内半定量(MSI)血流动力学参数对评价BI-RADS 4类乳腺肿瘤具有较好的鉴别诊断价值。
文摘The electric drive system characteristics of different projects for tracked vehicles are analyzed.For the two most typical projects,the parameters of power,torque and rotating speed and others of drive motor are figured out under the condition of satisfying adequate steering performance of the tracked vehicles.General opinions on the two projects are brought forward and conclusions are drawn.
基金supports of China NNSF(Grant No.60472063. 60325310)GDNSF/GDCNLF(04020074/ CN200402)
文摘In this paper,we suggest an adaptive watermarking method to improve both transparence and robustness of quantization index modulation(QIM) scheme. Instead of a fixed quantization step-size,we apply a step-size adapted to image content in each 8×8 block to make a balance of robust extraction and transparent embedding.The modified step-size is determined by contrast masking thresholds of Watson’s perceptual model.From a normalized crossed-correlation value between the original watermark and the detected watermark,we could observe that our method is robust to attacks of additive white Gaussian noise(AWGN),Salt and Pepper noise and Joint Photographic Experts Group(JPEG) compression than the original QIM.By taking into account the contrast insensitivity and visible thresholds of human visual system,the suggested improvement achieves a maximum embedding strength and an appropriate quantization step-size which is consistent with local values of a host signal.
