AIM:To evaluate different promising magnetic resonance imaging(MRI) methods at 7.0 Tesla(T) for the pre-stereotactic visualization of the zona incerta(ZI).METHODS:Two neuroradiologists qualitatively and quantitatively...AIM:To evaluate different promising magnetic resonance imaging(MRI) methods at 7.0 Tesla(T) for the pre-stereotactic visualization of the zona incerta(ZI).METHODS:Two neuroradiologists qualitatively and quantitatively examined T2-turbo spin-echo(T2-TSE),T1-weighted gradient-echo,as well as FLASH2D-T2Star and susceptibility-weighted imaging(SWI) for the visualization of the ZI at 7.0 T MRI.Delineation and image quality for the ZI were independently examined using a 6-scale grading system.Inter-rater reliability using Cohen's kappa coefficient(κ) were assessed.Contrast-tonoise ratios(CNR),and signal-to-noise ratios(SNR) for the ZI were calculated for all sequences.Differences in delineation,SNR,and CNR between the sequences were statistically assessed using a paired t-test.For the anatomic validation the coronal FLASH2D-T2Star images were co-registered with a stereotactic atlas(Schaltenbrand-Wahren).RESULTS:The rostral part of the ZI(rZI) could easily be identified and was best and reliably visualized in the coronal FLASH2D-T2Star images.The caudal part was not definable in any of the sequences.No major artifacts in the rZI were observed in any of the scans.FLASH2D-T2Star and SWI imaging offered significant higher CNR values for the rZI compared to T2-TSE images(P > 0.05).The co-registration of the coronal FLASH2D-T2Star images with the stereotactic atlas schema(Schaltenbrand-Wahren) confirmed the correct localization of the ZI in all cases.CONCLUSION:FLASH2D-T2Star imaging(particularly coronal view) provides the reliable and currently optimal visualization of the rZI at 7.0 T.These results can facilitate a better and more precise targeting of the caudal part of the ZI than ever before.展开更多
Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit ...Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit the problem sizes that can be simulated at industrial scale.The data structures used to store several millions of particles in such large-scale simulations have a large memory footprint that does not fit into the processor cache hierarchies on current high-performance-computing platforms,leading to reduced computational performance.This paper specifically addresses this aspect of memory access bottlenecks in industrial scale simulations.The use of space-flling curves to improve memory access patterns is described and their impact on computational performance is quantified in both shared and distributed memory parallelization paradigms.The Morton space flling curve applied to uniform grids and k-dimensional tree partitions are used to reorder the particle data-structure thus improving spatial and temporal locality in memory.The performance impact of these techniques when applied to two benchmark problems,namely the homogeneous-cooling-system and a fluidized-bed,are presented.These optimization techniques lead to approximately two-fold performance improvement in particle focused operations such as neighbor-list creation and data-exchange,with~1.5 times overall improvement in a fluidization simulation with 1.27 million particles.展开更多
文摘AIM:To evaluate different promising magnetic resonance imaging(MRI) methods at 7.0 Tesla(T) for the pre-stereotactic visualization of the zona incerta(ZI).METHODS:Two neuroradiologists qualitatively and quantitatively examined T2-turbo spin-echo(T2-TSE),T1-weighted gradient-echo,as well as FLASH2D-T2Star and susceptibility-weighted imaging(SWI) for the visualization of the ZI at 7.0 T MRI.Delineation and image quality for the ZI were independently examined using a 6-scale grading system.Inter-rater reliability using Cohen's kappa coefficient(κ) were assessed.Contrast-tonoise ratios(CNR),and signal-to-noise ratios(SNR) for the ZI were calculated for all sequences.Differences in delineation,SNR,and CNR between the sequences were statistically assessed using a paired t-test.For the anatomic validation the coronal FLASH2D-T2Star images were co-registered with a stereotactic atlas(Schaltenbrand-Wahren).RESULTS:The rostral part of the ZI(rZI) could easily be identified and was best and reliably visualized in the coronal FLASH2D-T2Star images.The caudal part was not definable in any of the sequences.No major artifacts in the rZI were observed in any of the scans.FLASH2D-T2Star and SWI imaging offered significant higher CNR values for the rZI compared to T2-TSE images(P > 0.05).The co-registration of the coronal FLASH2D-T2Star images with the stereotactic atlas schema(Schaltenbrand-Wahren) confirmed the correct localization of the ZI in all cases.CONCLUSION:FLASH2D-T2Star imaging(particularly coronal view) provides the reliable and currently optimal visualization of the rZI at 7.0 T.These results can facilitate a better and more precise targeting of the caudal part of the ZI than ever before.
文摘Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit the problem sizes that can be simulated at industrial scale.The data structures used to store several millions of particles in such large-scale simulations have a large memory footprint that does not fit into the processor cache hierarchies on current high-performance-computing platforms,leading to reduced computational performance.This paper specifically addresses this aspect of memory access bottlenecks in industrial scale simulations.The use of space-flling curves to improve memory access patterns is described and their impact on computational performance is quantified in both shared and distributed memory parallelization paradigms.The Morton space flling curve applied to uniform grids and k-dimensional tree partitions are used to reorder the particle data-structure thus improving spatial and temporal locality in memory.The performance impact of these techniques when applied to two benchmark problems,namely the homogeneous-cooling-system and a fluidized-bed,are presented.These optimization techniques lead to approximately two-fold performance improvement in particle focused operations such as neighbor-list creation and data-exchange,with~1.5 times overall improvement in a fluidization simulation with 1.27 million particles.
