scholarly journals The Direction-Dependence of Apparent Water Exchange Rate in Human White Matter

NeuroImage ◽  
2021 ◽  
pp. 118831
Author(s):  
Zhaoqing Li ◽  
Zhenfeng Pang ◽  
Juange Cheng ◽  
Yi-Cheng Hsu ◽  
Yi Sun ◽  
...  
Keyword(s):  
Exchange Rate ◽  
White Matter ◽  
Water Exchange ◽  
Water Exchange Rate ◽  
Direction Dependence

scholarly journals An Analytical Model for Estimating Water Exchange Rate in White Matter Using Diffusion MRI

PLoS ONE ◽  
2014 ◽  
Vol 9 (5) ◽  
pp. e95921 ◽  
Author(s):  
Esmaeil Davoodi-Bojd ◽  
Michael Chopp ◽  
Hamid Soltanian-Zadeh ◽  
Shiyang Wang ◽  
Guangliang Ding ◽  
...  
Keyword(s):  
Exchange Rate ◽  
White Matter ◽  
Analytical Model ◽  
Diffusion Mri ◽  
Water Exchange ◽  
Water Exchange Rate

scholarly journals Comparison Between Blood-Brain Barrier Water Exchange Rate and Permeability to Gadolinium-Based Contrast Agent in an Elderly Cohort

2020 ◽  
Vol 14 ◽  
Author(s):  
Xingfeng Shao ◽  
Kay Jann ◽  
Samantha J. Ma ◽  
Lirong Yan ◽  
Axel Montagne ◽  
...  
Keyword(s):  
At Risk ◽  
Exchange Rate ◽  
White Matter ◽  
Blood Brain Barrier ◽  
Water Exchange ◽  
Brain Regions ◽  
Elderly Subjects ◽  
Water Exchange Rate ◽  
Dce Mri ◽  
Bbb Permeability

Background: Dynamic contrast-enhanced (DCE) MRI using intravenous injection of gadolinium-based contrast agents (GBCAs) is commonly used for imaging blood-brain barrier (BBB) permeability. Water is an alternative endogenous tracer with limited exchange rate across the BBB. A direct comparison between BBB water exchange rate and BBB permeability to GBCA is missing. The purpose of this study was to directly compare BBB permeability to GBCA (Ktrans and kGad = Ktrans/Vp) and water exchange rate (kw) in a cohort of elderly subjects at risk of cerebral small vessel disease (cSVD).Methods: Ktrans/kGad and kw were measured by DCE-MRI and diffusion prepared pseudo-continuous arterial spin labeling (DP-pCASL), respectively, at 3 Tesla in 16 elderly subjects (3 male, age = 67.9 ± 3.0 yrs) at risk of cSVD. The test-retest reproducibility of kw measurements was evaluated with repeated scans ~6 weeks apart. Mixed effects linear regression was performed in the whole brain, gray matter (GM), white matter (WM), and 6 subcortical brain regions to investigate associations between Ktrans/kGad and test-retest kw. In addition, kw and Ktrans/kGad were compared in normal appearing white matter (NAWM), white matter hyperintensity (WMH) lesions and penumbra.Results: Significant correlation was found between kw and Ktrans only in WM (β = 6.7 × 104, P = 0.036), caudate (β = 8.6 × 104, P = 0.029), and middle cerebral artery (MCA) perforator territory (β = 6.9 × 104, P = 0.009), but not in the whole brain, GM or rest 5 brain regions. Significant correlation was found between kw and kGad in MCA perforator territory (β = 1.5 × 103, P = 0.049), medial-temporal lobe (β = 3.5 × 103, P = 0.032), and hippocampus (β = 3.4 × 103, P = 0.038), but not in the rest brain regions. Good reproducibility of kw measurements (ICC=0.75) was achieved. Ktrans was significantly lower inside WMH than WMH penumbra (16.2%, P = 0.026), and kGad was significantly lower in NAWM than in the WMH penumbra (20.8%, P < 0.001).Conclusion: kw provides a measure of water exchange rate across the BBB with good test-retest reproducibility. The BBB mechanism underlying kw and Ktrans/kGad is likely to be different, as manifested by correlations in only three brain regions for each pair of comparison between kw and Ktrans or kGad.

scholarly journals Study on Water Exchange and Water Quality Simulation of Macao Airport Expansion Project

2021 ◽  
Vol 261 ◽  
pp. 03019
Author(s):  
Huang Pengfei ◽  
Liu Pei ◽  
Xu Wei
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Exchange Rate ◽  
Water Exchange ◽  
Exchange Capacity ◽  
Two Dimensional ◽  
Water Exchange Rate ◽  
Water Quality Simulation ◽  
Significant Difference ◽  
Better Than

In this paper, we analyzed the current situation of water pollution sources near Macao airport, established a two-dimensional water exchange and water quality mathematical model near the project, and compared and simulated the reclamation schemes of Macao airport. According to the results of water exchange and COD calculation of water quality, the 80 m channel scheme was remarkably better than the 40 m one in terms of water exchange capacity and the possibility of achieving the water quality target. However, with the increase of channel width, the variation of water exchange rate and half exchange period would slow down. There was no significant difference in water exchange rate, water exchange period and water quality distribution between 80m channel and 120 m channel. The final scheme was to adopt the 80 m channel.

Accelerating water exchange in GdIII–DO3A-derivatives by favouring the dissociative mechanism through hydrogen bonding

2019 ◽  
Vol 55 (4) ◽  
pp. 513-516 ◽  
Author(s):  
Loredana Leone ◽  
David Esteban-Gómez ◽  
Carlos Platas-Iglesias ◽  
Marco Milanesio ◽  
Lorenzo Tei
Keyword(s):  
Hydrogen Bonding ◽  
Exchange Rate ◽  
Water Exchange ◽  
Exchange Mechanism ◽  
Water Molecules ◽  
Dissociative Mechanism ◽  
Water Exchange Rate ◽  
Order Of Magnitude

The water exchange rate in GdIII-complexes increases by one order of magnitude due to H-bonding between the phenol(ate) group and the water molecules involved in the dissociative exchange mechanism.

Unexpectedly Large Change of Water Exchange Rate and Mechanism on [Ln(DTPA-BMA)(H2O)] Complexes along the Lanthanide(III) Series

1995 ◽  
Vol 34 (17) ◽  
pp. 4447-4453 ◽  
Author(s):  
Dirk Pubanz ◽  
Gabriel Gonzalez ◽  
D. Hugh Powell ◽  
Andre E. Merbach
Keyword(s):  
Exchange Rate ◽  
Water Exchange ◽  
Large Change ◽  
Water Exchange Rate

scholarly journals Electronic Effects of the Substituents on Relaxometric and CEST Behaviour of Ln(III)-DOTA-Tetraanilides

Inorganics ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 43
Author(s):  
Valeria Lagostina ◽  
Loredana Leone ◽  
Fabio Carniato ◽  
Giuseppe Digilio ◽  
Lorenzo Tei ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Water Exchange ◽  
Chemical Exchange ◽  
Chemical Exchange Saturation Transfer ◽  
Saturation Transfer ◽  
Electronic Effects ◽  
17O Nmr ◽  
Water Exchange Rate ◽  
Coordinated Water ◽  
The Eu

Three different 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetamide (DOTAM) derivatives bearing as amide N-substituents phenyl, p-methoxyphenyl and p-ethylbenzoate groups were synthesized and the 1H and 17O NMR relaxometric behaviour of the Gd(III)-chelates and chemical exchange saturation transfer (CEST) effect of the Eu(III) complexes were evaluated. The electronic properties of the substituents were shown to strongly influence the coordinated water exchange rate (kex), resulting in five times faster kex for the electron donating phenylmethoxy group compared to the electron withdrawing ethylbenzoate group.

Study on the Improvement Method of Water Exchange Rate for Shuidong Bay Using Numerical Model

2013 ◽  
Vol 765-767 ◽  
pp. 799-804
Author(s):  
Shan Shan Yao ◽  
Ming Xiao Xie
Keyword(s):  
Exchange Rate ◽  
Numerical Model ◽  
Diffusion Equation ◽  
Water Exchange ◽  
Water Exchange Rate ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Conservative Tracer ◽  
Comprehensive Comparison ◽  
Improvement Method

Using a numerical model based on the hydrodynamics and advection-diffusion equation, the water exchange capability of the Shuidong Bay was firstly simulated, then the water exchange rate of three regualation scenarios were calculated through the concentration variation of dissolved conservative tracer. The calculated results show that the water exchange rate of the Shuidong Bay is only about 65% after 30d under current condition.When bay was dredged to bottom elevation-3.0m, the water exchange rate can greatly increase to 88% after 30d. However, the water exchage rate has not significantly increased or even decreased after further dredging. Through comprehensive comparison, it is suggested to dredge the Shuidong Bay, and the dredging bottom elevation of-3.0m is the most suitable.

Sign in / Sign up

Export Citation Format

Share Document