scholarly journals The Influence of Demographics and Vascular Risk Factors on Glymphatic Function Measured by Diffusion Along Perivascular Space

2021 ◽  
Vol 13 ◽  
Author(s):  
Yao Zhang ◽  
Ruiting Zhang ◽  
Yongquan Ye ◽  
Shuyue Wang ◽  
Yeerfan Jiaerken ◽  
...  
Keyword(s):  
Risk Factors ◽  
Animal Studies ◽  
Diffusion Tensor ◽  
Perivascular Space ◽  
Brain Diseases ◽  
Imaging Method ◽  
Imaging Data ◽  
Potential Index ◽  
The Alps

Assessing glymphatic function using in-vivo imaging method is of great value for understanding its contribution to major brain diseases. In the present study, we aim to validate the association between a variety of risk factors and a potential index of glymphatic function—Diffusion Tensor Image Analysis Along the Perivascular Space (ALPS index). We enrolled 142 subjects from communities and performed multi-modality magnetic resonance imaging scans. The ALPS index was calculated from diffusion tensor imaging data, and its associations with demographic factors, vascular factors were investigated using regression analyses. We found that the ALPS index was negatively associated with age (β = −0.284, p < 0.001). Compared to males, females had significantly higher ALPS index (β = −0.243, p = 0.001). Hypertensive subjects had significantly lower ALPS index compared to non-hypertensive subjects (β = −0.189, p = 0.013). Furthermore, venous disruption could decrease ALPS index (β = −0.215, p = 0.003). In general, our results are in consistent with previous conceptions and results from animal studies about the pathophysiology of glymphatic dysfunction. Future studies utilizing this method should consider introducing the above-mentioned factors as important covariates.

scholarly journals Reproducibility of diffusion tensor image analysis along the perivascular space (DTI-ALPS) for evaluating interstitial fluid diffusivity and glymphatic function: CHanges in Alps index on Multiple conditiON acquIsition eXperiment (CHAMONIX) study

2021 ◽  
Author(s):  
Toshiaki Taoka ◽  
Rintaro Ito ◽  
Rei Nakamichi ◽  
Koji Kamagata ◽  
Mayuko Sakai ◽  
...  
Keyword(s):  
Image Analysis ◽  
Interstitial Fluid ◽  
Diffusion Tensor ◽  
Head Position ◽  
Perivascular Space ◽  
Imaging Method ◽  
Imaging Sequence ◽  
The Alps ◽  
Index Value ◽  
Imaging Plane

Abstract Purpose The diffusion tensor image analysis along the perivascular space (DTI-ALPS) method was developed to evaluate the brain’s glymphatic function or interstitial fluid dynamics. This study aimed to evaluate the reproducibility of the DTI-ALPS method and the effect of modifications in the imaging method and data evaluation. Materials and methods Seven healthy volunteers were enrolled in this study. Image acquisition was performed for this test–retest study using a fixed imaging sequence and modified imaging methods which included the placement of region of interest (ROI), imaging plane, head position, averaging, number of motion-proving gradients, echo time (TE), and a different scanner. The ALPS-index values were evaluated for the change of conditions listed above. Results This test–retest study by a fixed imaging sequence showed very high reproducibility (intraclass coefficient = 0.828) for the ALPS-index value. The bilateral ROI placement showed higher reproducibility. The number of averaging and the difference of the scanner did not influence the ALPS-index values. However, modification of the imaging plane and head position impaired reproducibility, and the number of motion-proving gradients affected the ALPS-index value. The ALPS-index values from 12-axis DTI and 3-axis diffusion-weighted image (DWI) showed good correlation (r = 0.86). Also, a shorter TE resulted in a larger value of the ALPS-index. Conclusion ALPS index was robust under the fixed imaging method even when different scanners were used. ALPS index was influenced by the imaging plane, the number of motion-proving gradient axes, and TE in the imaging sequence. These factors should be uniformed in the planning ALPS method studies. The possibility to develop a 3-axis DWI-ALPS method using three axes of the motion-proving gradient was also suggested.

scholarly journals Method for Calibration of Left Ventricle Material Properties Using Three-Dimensional Echocardiography Endocardial Strains

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Yaghoub Dabiri ◽  
Kevin L. Sack ◽  
Nuno Rebelo ◽  
Peter Wang ◽  
Yunjie Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Left Ventricle ◽  
Diffusion Tensor ◽  
Diastolic Pressure ◽  
Three Dimensional ◽  
Heart Association ◽  
Mean Difference ◽  
Imaging Data ◽  
The Mean

We sought to calibrate mechanical properties of left ventricle (LV) based on three-dimensional (3D) speckle tracking echocardiographic imaging data recorded from 16 segments defined by American Heart Association (AHA). The in vivo data were used to create finite element (FE) LV and biventricular (BV) models. The orientation of the fibers in the LV model was rule based, but diffusion tensor magnetic resonance imaging (MRI) data were used for the fiber directions in the BV model. A nonlinear fiber-reinforced constitutive equation was used to describe the passive behavior of the myocardium, whereas the active tension was described by a model based on tissue contraction (Tmax). isight was used for optimization, which used abaqus as the forward solver (Simulia, Providence, RI). The calibration of passive properties based on the end diastolic pressure volume relation (EDPVR) curve resulted in relatively good agreement (mean error = −0.04 ml). The difference between the experimental and computational strains decreased after segmental strain metrics, rather than global metrics, were used for calibration: for the LV model, the mean difference reduced from 0.129 to 0.046 (circumferential) and from 0.076 to 0.059 (longitudinal); for the BV model, the mean difference nearly did not change in the circumferential direction (0.061) but reduced in the longitudinal direction from 0.076 to 0.055. The calibration of mechanical properties for myocardium can be improved using segmental strain metrics. The importance of realistic fiber orientation and geometry for modeling of the LV was shown.

The Use of Magnetic Resonance Imaging to Estimate the Mass of the Pectoralis Muscle of Chickens In Vivo

1994 ◽  
Vol 1994 ◽  
pp. 50-50
Author(s):  
N.D. Scollan ◽  
L.J. Caston ◽  
Z. Liu ◽  
A.K. Zubair ◽  
S. Leeson ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Broiler Chickens ◽  
Animal Studies ◽  
Whole Body ◽  
Imaging Method ◽  
Resonance Imaging ◽  
Body Images ◽  
Tissue Samples

In studies of animal growth it is often necessary to assess whole body composition or organ size prior to and during the course of a particular treatment. Nuclear Magnetic Resonance (NMR) offers the possibility to achieve these measurements on the same animal and in a non-invasive fashion. The use of NMR in attaining body images, referred to as Magnetic Resonance Imaging (MRI), has developed as the imaging method of choice for humans, due to its excellent soft tissue contrast and use of nonionizing radiation. The use of NMR in animal studies has been limited, which is probably related to the availability of suitable facilities and the cost of using them. However, several research groups have applied it to determining fat and water content of tissue samples and intact animals (Mitchell et al., 1991; Scollan et al., 1993). The aim of this study was to evaluate the use of MRI to determine the size (volume) and shape of the Pectoralis muscle (Pectoralis major and minor) in broiler chickens, non-invasively and in vivo.

scholarly journals The Connectivity of the Human Pulvinar: A Diffusion Tensor Imaging Tractography Study

2008 ◽  
Vol 2008 ◽  
pp. 1-5 ◽  
Author(s):  
Sandra E. Leh ◽  
M. Mallar Chakravarty ◽  
Alain Ptito
Keyword(s):  
Diffusion Tensor Imaging ◽  
Visual Processing ◽  
Animal Studies ◽  
Diffusion Tensor ◽  
Human Vision ◽  
Subcortical Structures ◽  
Fiber Tracts ◽  
Visual Spatial ◽  
Visual Areas

Previous studies in nonhuman primates and cats have shown that the pulvinar receives input from various cortical and subcortical areas involved in vision. Although the contribution of the pulvinar to human vision remains to be established, anatomical tracer and electrophysiological animal studies on cortico-pulvinar circuits suggest an important role of this structure in visual spatial attention, visual integration, and higher-order visual processing. Because methodological constraints limit investigations of the human pulvinar's function, its role could, up to now, only be inferred from animal studies. In the present study, we used an innovative imaging technique, Diffusion Tensor Imaging (DTI) tractography, to determine cortical and subcortical connections of the human pulvinar. We were able to reconstruct pulvinar fiber tracts and compare variability across subjects in vivo. Here we demonstrate that the human pulvinar is interconnected with subcortical structures (superior colliculus, thalamus, and caudate nucleus) as well as with cortical regions (primary visual areas (area 17), secondary visual areas (area 18, 19), visual inferotemporal areas (area 20), posterior parietal association areas (area 7), frontal eye fields and prefrontal areas). These results are consistent with the connectivity reported in animal anatomical studies.

In Vivo Characterization of Transport Anisotropy in Rat Spinal Cord Using Diffusion Tensor Imaging

2008 ◽  
Author(s):  
Xiaoming Chen ◽  
Garrett W. Astary ◽  
Thomas H. Mareci ◽  
Malisa Sarntinoranont
Keyword(s):  
Spinal Cord ◽  
Diffusion Tensor Imaging ◽  
Drug Transport ◽  
Diffusion Tensor ◽  
Local Drug Delivery ◽  
Imaging Method ◽  
Rat Spinal Cord ◽  
In Vivo Characterization

Biotransport in nervous tissues is complicated by the existence of neural fibers. These axonal fibers result in inhomogeneous and anisotropic extracellular transport, which complicates the prediction of local drug delivery such as convection-enhanced delivery [1]. Previous studies by our group [4] have shown that by using diffusion tensor imaging (DTI) [2, 3], anisotropic transport in rat spinal cord can be modeled using computational models, and consequently extracellular flows which influence drug transport can be well predicted. In previous studies, DTI-based models used data from an excised and fixed rat spinal cord. In the current study, we extend our DTI study to in vivo measures, and report the in vivo characterization of transport anisotropy in rat spinal cord. The MR imaging method is presented and the DTI data is discussed.

scholarly journals Diffusion tensor-MRI detects exercise-induced neuroplasticity in the hippocampal microstructure in mice

2020 ◽  
Vol 5 (2) ◽  
pp. 147-159
Author(s):  
Mohammad R. Islam ◽  
Renhao Luo ◽  
Sophia Valaris ◽  
Erin B. Haley ◽  
Hajime Takase ◽  
...  
Keyword(s):  
Animal Studies ◽  
Wheel Running ◽  
Diffusion Tensor ◽  
Hippocampal Volume ◽  
Mri Scans ◽  
Oligodendrocyte Precursor ◽  
Exercise Induced ◽  
Response To Exercise ◽  
The Brain

Background: Despite considerable research on exercise-induced neuroplasticity in the brain, a major ongoing challenge in translating findings from animal studies to humans is that clinical and preclinical settings employ very different techniques. Objective: Here we aim to bridge this divide by using diffusion tensor imaging MRI (DTI), an advanced imaging technique commonly applied in human studies, in a longitudinal exercise study with mice. Methods: Wild-type mice were exercised using voluntary free-wheel running, and MRI scans were at baseline and after four weeks and nine weeks of running. Results: Both hippocampal volume and fractional anisotropy, a surrogate for microstructural directionality, significantly increased with exercise. In addition, exercise levels correlated with effect size. Histological analysis showed more PDGFRα+ oligodendrocyte precursor cells in the corpus callosum of running mice. Conclusions: These results provide compelling in vivo support for the concept that similar adaptive changes occur in the brains of mice and humans in response to exercise.

scholarly journals Probing tissue microstructure by diffusion skewness tensor imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lipeng Ning ◽  
Filip Szczepankiewicz ◽  
Markus Nilsson ◽  
Yogesh Rathi ◽  
Carl-Fredrik Westin
Keyword(s):  
Diffusion Processes ◽  
Diffusion Tensor ◽  
Fundamental Problem ◽  
Medical Science ◽  
Synthetic Data ◽  
Full Rank ◽  
Imaging Data ◽  
Tissue Microstructure ◽  
Diffusion Tensors

AbstractProbing the cellular structure of in vivo biological tissue is a fundamental problem in biomedical imaging and medical science. This work introduces an approach for analyzing diffusion magnetic resonance imaging data acquired by the novel tensor-valued encoding technique for characterizing tissue microstructure. Our approach first uses a signal model to estimate the variance and skewness of the distribution of apparent diffusion tensors modeling the underlying tissue. Then several novel imaging indices, such as weighted microscopic anisotropy and microscopic skewness, are derived to characterize different ensembles of diffusion processes that are indistinguishable by existing techniques. The contributions of this work also include a theoretical proof that shows that, to estimate the skewness of a diffusion tensor distribution, the encoding protocol needs to include full-rank tensor diffusion encoding. This proof provides a guideline for the application of this technique. The properties of the proposed indices are illustrated using both synthetic data and in vivo data acquired from a human brain.

scholarly journals Population neuroimaging: generation of a comprehensive data resource within the ALSPAC pregnancy and birth cohort

2020 ◽  
Vol 5 ◽  
pp. 203
Author(s):  
Tamsin H. Sharp ◽  
Nancy S. McBride ◽  
Amy E. Howell ◽  
C. John Evans ◽  
Derek K. Jones ◽  
...  
Keyword(s):  
Birth Cohort ◽  
Diffusion Tensor ◽  
Magnetization Transfer ◽  
Valuable Insight ◽  
Imaging Data ◽  
Data Resource ◽  
Parents And Children ◽  
Neuroimaging Data ◽  
Pregnancy And Birth

Neuroimaging offers a valuable insight into human brain development by allowing in vivo assessment of structure, connectivity and function. Multimodal neuroimaging data have been obtained as part of three sub-studies within the Avon Longitudinal Study of Parents and Children, a prospective multigenerational pregnancy and birth cohort based in the United Kingdom. Brain imaging data were acquired when offspring were between 18 and 24 years of age, and included acquisition of structural, functional and magnetization transfer magnetic resonance, diffusion tensor, and magnetoencephalography imaging. This resource provides a unique opportunity to combine neuroimaging data with extensive phenotypic and genotypic measures from participants, their mothers, and fathers.

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