The generalized Stejskal-Tanner equation for non-uniform magnetic field gradients

Simulated body fluids (SBFs) that mimic human blood plasma are widely used media for in vitro studies in an extensive array of research fields, from biomineralization to surface and corrosion sciences. We show that these solutions undergo dynamic nanoscopic conformational rearrangements on the timescale of minutes to hours, even though they are commonly considered stable or metastable. In particular, we find and characterize nanoscale inhomogeneities made of calcium phosphate (CaP) aggregates that emerge from homogeneous SBFs within a few hours and evolve into prenucleation species (PNS) that act as precursors in CaP crystallization processes. These ionic clusters consist of ∼2 nm large spherical building units that can aggregate into suprastructures with sizes of over 200 nm. We show that the residence times of phosphate ions in the PNS depend critically on the total PNS surface. These findings are particularly relevant for understanding nonclassical crystallization phenomena, in which PNS are assumed to act as building blocks for the final crystal structure.

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“…Diffusion coefficients were extracted using monoexponential fits to the Stejskal–Tanner equation. 47 …”

Section: Methodsmentioning

confidence: 99%

Formation and Evolution of Nanoscale Calcium Phosphate Precursors under Biomimetic Conditions

et al. 2021

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“…Moreover, comparisons should be made according to gender (male, female), age (20s~70s), subgroups (Control vs Post Traumatic Stress Disorder, etc. ), various brain imaging systems (Electroencephalography, EEG/Diffusion Tensor Imaging, DTI/B-spatial distribution in DTI [ 43 , 44 ], BSD-DTI [ 43 , 44 ], and so on), and driving experience (novice drivers, experienced drivers) since the subjects of this study only consisted of men in their twenties with limited driving experience. Dynamic causal modeling, utilized in the analysis section of the present study, has the following limitations.…”

Section: Discussionmentioning

confidence: 99%

Effective Connectivity Analysis of Brain Activated Regions during Distracted Driving

et al. 2021

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This study aims to use functional magnetic resonance imaging (fMRI) to assess the effective connectivity between the regions of the brain activated when driving and performing a secondary task (addition task). The subjects used an MR-compatible driving simulator ㅊ to manipulate the driving wheel with both hands and control the pedals (accelerator and brake) with their right foot as if they were driving in an actual environment. Effective connectivity analysis was performed for three regions of the right and the left hemispheres with the highest z-scores, and six of the regions of the entire brain (right and left hemisphere) activated during driving by dynamic causal modeling (DCM). In the right hemisphere, a motor control pathway related to movement control for driving performance was discovered; in the left hemisphere, the pathways in the regions related to movement control for driving performance, starting with the region associated with the secondary task, were discovered. In the whole brain, connectivity was discovered in each of the right and left hemispheres. The motor network of declarative memory, which is the connectivity of the right thalamus, left lingual gyrus, and right precentral gyrus, was worth noting. These results seem meaningful, as they demonstrate the connectivity associated with the control of voluntary movement related to memory from human experience, although limited to driving tasks.

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“…A recent investigation of the magnetic field's influence showed the existence and importance of systematic errors related to the use of hardware and the implementation of specific sequences [51–53]. There was a presence of concomitant field and eddy currents in the nonunity of the signal distribution generated by the gradient and RF coils, which resulted in B-matrix inhomogeneity [54]. These factors are, in part, responsible for the observed incompatibilities in this study, especially due to the use of sensitive echo-planar imaging (EPI) sequences.…”

Section: Discussionmentioning

confidence: 99%

Influence of Acquisition Time on MR Image Quality Estimated with Nonparametric Measures Based on Texture Features

Obuchowicz

Piórkowski

Urbanik

et al. 2019

BioMed Research International

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Correlation of parametrized image texture features (ITF) analyses conducted in different regions of interest (ROIs) overcomes limitations and reliably reflects image quality. The aim of this study is to propose a nonparametrical method and classify the quality of a magnetic resonance (MR) image that has undergone controlled degradation by using textural features in the image. Images of 41 patients, 17 women and 24 men, aged between 23 and 56 years were analyzed. T2-weighted sagittal sequences of the lumbar spine, cervical spine, and knee and T2-weighted coronal sequences of the shoulder and wrist were generated. The implementation of parallel imaging with the use of GRAPPA2, GRAPPA3, and GRAPPA4 led to a substantial reduction in the scanning time but also degraded image quality. The number of degraded image textural features was correlated with the scanning time. Longer scan times correlated with markedly higher ITF image persistence in comparison with images computed with reduced scan times. Higher ITF preservation was observed in images of bones in the spine and femur as compared to images of soft tissues, i.e., tendons and muscles. Finally, a nonparametrized image quality assessment based on an analysis of the ITF, computed for different tissues, correlating with the changes in acquisition time of the MR images, was successfully developed. The correlation between acquisition time and the number of reproducible features present in an MR image was found to yield the necessary assumptions to calculate the quality index.

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The generalized Stejskal-Tanner equation for non-uniform magnetic field gradients

Cited by 23 publications

References 16 publications

Formation and Evolution of Nanoscale Calcium Phosphate Precursors under Biomimetic Conditions

Formation and Evolution of Nanoscale Calcium Phosphate Precursors under Biomimetic Conditions

Effective Connectivity Analysis of Brain Activated Regions during Distracted Driving

Influence of Acquisition Time on MR Image Quality Estimated with Nonparametric Measures Based on Texture Features

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