School-age children are in a specific development stage corresponding to juvenility,when the white matter of the brain experiences ongoing maturation.Dffusion-weighted magnetic resonance imaging(DWI),especially diffus...School-age children are in a specific development stage corresponding to juvenility,when the white matter of the brain experiences ongoing maturation.Dffusion-weighted magnetic resonance imaging(DWI),especially diffusion tensor imaging(DTI),is extensively used to characterize the maturation by assessing white matter properties in vivo.In the analysis of DWI data,spatial normalization is crucial for conducting inter-subject analyses or linking the individual space with the reference space.Using tensor-based registration with an appropriate diffusion tensor template presents high accuracy regarding spatial normalization.However,there is a lack of a standardized diffusion tensor template dedicated to school-age children with ongoing brain development.Here,we established the school-age children diffusion tensor(SACT)template by optimizing tensor reorientation on high-quality DTI data from a large sample of cognitively normal participants aged 6-12 years.With an age-balanced design,the SACT template represented the entire age range well by showing high similarity to the age-specific templates.Compared with the tensor template of adults,the SACT template revealed significantly higher spatial normalization accuracy and inter-subject coherence upon evaluation of subjects in two different datasets of schoolage children.A practical application regarding the age associations with the normalized DTI-derived data was conducted to further compare the SACT template and the adult template.Although similar spatial patterns were found,the SACT template showed significant effects on the distributions of the statistical results,which may be related to the performance of spatial normalization.Looking forward,the SACT template could contribute to future studies of white matter development in both healthy and clinical populations.The SACT template is publicly available now(tp://igshare com/aricles/dataseu'SACT_.template/14071283).展开更多
针对现有I帧错误隐藏方法不能平衡恢复图像质量与算法复杂度的问题,提出了一种高效的I帧分区错误隐藏方法。首先,利用视频帧之间的运动相关性将丢失宏块分为运动宏块和静止宏块。对于静止宏块,采用帧拷贝法进行掩盖;对于运动宏块,再根...针对现有I帧错误隐藏方法不能平衡恢复图像质量与算法复杂度的问题,提出了一种高效的I帧分区错误隐藏方法。首先,利用视频帧之间的运动相关性将丢失宏块分为运动宏块和静止宏块。对于静止宏块,采用帧拷贝法进行掩盖;对于运动宏块,再根据其周围正确解码宏块的纹理信息将其分为平滑块和纹理块。对平滑块采用双线性插值法进行恢复;对纹理块利用比较精细的指数分布权重的加权模板匹配(WTE)法进行掩盖。实验结果表明,与WTE算法相比,所提方法的峰值信噪比(PSNR)平均提高了2.6 d B,计算复杂度平均降低了90%。对于场景连续的具有不同特征和分辨率的视频序列,所提方法都具有一定的适用性。展开更多
基金supported by the Beijing Brain Initiative of Beijing Municipal Science&Technology Commission(Z1811001518003)the National Natural Science Foundation of China(31521063)All the authors thank the National Center for Protein Sciences at Peking University for assistance_with brain scanning.The authors thank the"2019 Helmholtz-OCPC-Program for the involvement of postdocs in bilateral collaboration projects"for financial support that enabled this important study,Allthe authors are grateful for the contribution of the participants to the CBD project and the open access to the NKI-Rockiand sample.
文摘School-age children are in a specific development stage corresponding to juvenility,when the white matter of the brain experiences ongoing maturation.Dffusion-weighted magnetic resonance imaging(DWI),especially diffusion tensor imaging(DTI),is extensively used to characterize the maturation by assessing white matter properties in vivo.In the analysis of DWI data,spatial normalization is crucial for conducting inter-subject analyses or linking the individual space with the reference space.Using tensor-based registration with an appropriate diffusion tensor template presents high accuracy regarding spatial normalization.However,there is a lack of a standardized diffusion tensor template dedicated to school-age children with ongoing brain development.Here,we established the school-age children diffusion tensor(SACT)template by optimizing tensor reorientation on high-quality DTI data from a large sample of cognitively normal participants aged 6-12 years.With an age-balanced design,the SACT template represented the entire age range well by showing high similarity to the age-specific templates.Compared with the tensor template of adults,the SACT template revealed significantly higher spatial normalization accuracy and inter-subject coherence upon evaluation of subjects in two different datasets of schoolage children.A practical application regarding the age associations with the normalized DTI-derived data was conducted to further compare the SACT template and the adult template.Although similar spatial patterns were found,the SACT template showed significant effects on the distributions of the statistical results,which may be related to the performance of spatial normalization.Looking forward,the SACT template could contribute to future studies of white matter development in both healthy and clinical populations.The SACT template is publicly available now(tp://igshare com/aricles/dataseu'SACT_.template/14071283).
文摘针对现有I帧错误隐藏方法不能平衡恢复图像质量与算法复杂度的问题,提出了一种高效的I帧分区错误隐藏方法。首先,利用视频帧之间的运动相关性将丢失宏块分为运动宏块和静止宏块。对于静止宏块,采用帧拷贝法进行掩盖;对于运动宏块,再根据其周围正确解码宏块的纹理信息将其分为平滑块和纹理块。对平滑块采用双线性插值法进行恢复;对纹理块利用比较精细的指数分布权重的加权模板匹配(WTE)法进行掩盖。实验结果表明,与WTE算法相比,所提方法的峰值信噪比(PSNR)平均提高了2.6 d B,计算复杂度平均降低了90%。对于场景连续的具有不同特征和分辨率的视频序列,所提方法都具有一定的适用性。
