scholarly journals Quantitative Assessment of Water Pools by T1p and T2p MRI in Acute Cerebral Ischemia of the Rat

2008 ◽  
Vol 29 (1) ◽  
pp. 206-216 ◽  
Author(s):  
Kimmo T Jokivarsi ◽  
Juha-Pekka Niskanen ◽  
Shalom Michaeli ◽  
Heidi I Gröhn ◽  
Michael Garwood ◽  
...  
Keyword(s):  
Correlation Time ◽  
Continuous Wave ◽  
Vasogenic Edema ◽  
Free Water ◽  
Rotating Frame ◽  
Mri Contrast ◽  
Water Fraction ◽  
Acute Cerebral Ischemia ◽  
Rotating Frame Relaxation

The rotating frame longitudinal relaxation magnetic resonance imaging (MRI) contrast, T1ρ, obtained with on-resonance continuous wave (CW) spin-lock field is a sensitive indicator of tissue changes associated with hyperacute stroke. Here, the rotating frame relaxation concept was extended by acquiring both T1ρ and transverse rotating frame ( T2ρ) MRI data using both CW and adiabatic hyperbolic secant (HSn; n = 1, 4, or 8) pulses in a rat stroke model of middle cerebral artery occlusion. The results show differences in the sensitivity of spinlock T1ρ and T2ρ MRI to detect hyperacute ischemia. The most sensitive techniques were CW- T1ρ and T1ρ using HS4 or HS8 pulses. Fitting a two-pool exchange model to the T1ρ and T2ρ MRI data acquired from the infarcting brain indicated time-dependent increase in free water fraction, decrease in the correlation time of water fraction associated with macromolecules, and increase in the exchange correlation time. These findings are consistent with known pathology in acute stroke, including vasogenic edema, destructive processes, and tissue acidification. Our results show that the sensitivity of the spinlock MRI contrast in vivo can be modified using different spinlock preparation blocks, and that physicochemical models of the rotating frame relaxation may provide insight into progression of ischemia in vivo.

scholarly journals Frequency offset dependence of adiabatic rotating frame relaxation rate constants: relevance to MRS investigations of metabolite dynamics in vivo

2011 ◽  
Vol 24 (7) ◽  
pp. 807-814 ◽  
Author(s):  
Silvia Mangia ◽  
Timo Liimatainen ◽  
Michael Garwood ◽  
Ivan Tkac ◽  
Pierre-Gilles Henry ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Frequency Offset ◽  
Rotating Frame ◽  
Rotating Frame Relaxation

Longitudinal rotating frame relaxation time measurements in infarcted mouse myocardium in vivo

2012 ◽  
Vol 69 (5) ◽  
pp. 1389-1395 ◽  
Author(s):  
Haja-Sherief N. Musthafa ◽  
Galina Dragneva ◽  
Line Lottonen ◽  
Mari Merentie ◽  
Lyubomir Petrov ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Rotating Frame ◽  
Rotating Frame Relaxation

scholarly journals Neurite orientation and dispersion density imaging (NODDI) detects cortical and corticospinal tract degeneration in ALS

2018 ◽  
Vol 90 (4) ◽  
pp. 404-411 ◽  
Author(s):  
Rebecca J Broad ◽  
Matt C Gabel ◽  
Nicholas G Dowell ◽  
David J Schwartzman ◽  
Anil K Seth ◽  
...  
Keyword(s):  
Diffusion Mri ◽  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Free Water ◽  
Cortical Atrophy ◽  
Precentral Gyrus ◽  
Water Fraction ◽  
Sporadic Als ◽  
The Right

BackgroundCorticospinal tract (CST) degeneration and cortical atrophy are consistent features of amyotrophic lateral sclerosis (ALS). We hypothesised that neurite orientation dispersion and density imaging (NODDI), a multicompartment model of diffusion MRI, would reveal microstructural changes associated with ALS within the CST and precentral gyrus (PCG) ‘in vivo’.Methods23 participants with sporadic ALS and 23 healthy controls underwent diffusion MRI. Neurite density index (NDI), orientation dispersion index (ODI) and free water fraction (isotropic compartment (ISO)) were derived. Whole brain voxel-wise analysis was performed to assess for group differences. Standard diffusion tensor imaging (DTI) parameters were computed for comparison. Subgroup analysis was performed to investigate for NODDI parameter differences relating to bulbar involvement. Correlation of NODDI parameters with clinical variables were also explored. The results were accepted as significant where p<0.05 after family-wise error correction at the cluster level, clusters formed with p<0.001.ResultsIn the ALS group NDI was reduced in the extensive regions of the CST, the corpus callosum and the right PCG. ODI was reduced in the right anterior internal capsule and the right PCG. Significant differences in NDI were detected between subgroups stratified according to the presence or absence of bulbar involvement. ODI and ISO correlated with disease duration.ConclusionsNODDI demonstrates that axonal loss within the CST is a core feature of degeneration in ALS. This is the main factor contributing to the altered diffusivity profile detected using DTI. NODDI also identified dendritic alterations within the PCG, suggesting microstructural cortical dendritic changes occur together with CST axonal damage.

T1ρ MRI contrast in the human brain: Modulation of the longitudinal rotating frame relaxation shutter-speed during an adiabatic RF pulse

2006 ◽  
Vol 181 (1) ◽  
pp. 135-147 ◽  
Author(s):  
Shalom Michaeli ◽  
Dennis J. Sorce ◽  
Charles S. Springer ◽  
Kamil Ugurbil ◽  
Michael Garwood
Keyword(s):  
Human Brain ◽  
Rotating Frame ◽  
Mri Contrast ◽  
Rotating Frame Relaxation ◽  
Rf Pulse ◽  
Shutter Speed

scholarly journals Biocompatibility of Bacterial Magnetosomes as MRI Contrast Agent: A Long-Term In Vivo Follow-Up Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1235
Author(s):  
Xiaohui Nan ◽  
Wenjia Lai ◽  
Dan Li ◽  
Jiesheng Tian ◽  
Zhiyuan Hu ◽  
...  
Keyword(s):  
Contrast Agent ◽  
Magnetic Domain ◽  
Bilayer Membrane ◽  
The Body ◽  
Mri Contrast Agent ◽  
Mri Imaging ◽  
Mri Contrast

Derived from magnetotactic bacteria (MTB), magnetosomes consist of magnetite crystals enclosed within a lipid bilayer membrane and are known to possess advantages over artificially synthesized nanoparticles because of the narrow size distribution, uniform morphology, high purity and crystallinity, single magnetic domain, good biocompatibility, and easy surface modification. These unique properties have increasingly attracted researchers to apply bacterial magnetosomes (BMs) in the fields of biology and medicine as MRI imaging contrast agents. Due to the concern of biosafety, a long-term follow-up of the distribution and clearance of BMs after entering the body is necessary. In this study, we tracked changes of BMs in major organs of mice up to 135 days after intravenous injection using a combination of several techniques. We not only confirmed the liver as the well-known targeted organs of BMs, but also found that BMs accumulated in the spleen. Besides, two major elimination paths, as well as the approximate length of time for BMs to be cleared from the mice, were revealed. Together, the results not only confirm that BMs have high biocompatibility, but also provide a long-term in-vivo assessment which may further help to forward the clinical applications of BMs as an MRI contrast agent.

scholarly journals Study on Establishing Reference Safe Concentrations of MRI Contrast Agents for Optimized Images: Paramagnetic Gd-DTPA-BMEA and Superparamagnetic Ferucarbotran

2021 ◽  
Vol 11 (3) ◽  
pp. 1165
Author(s):  
Wen-Tien Hsiao ◽  
Yi-Hong Chou ◽  
Jhong-Wei Tu ◽  
Ai-Yih Wang ◽  
Lu-Han Lai
Keyword(s):  
Contrast Agent ◽  
Contrast Agents ◽  
Mri Contrast Agents ◽  
Mri Contrast Agent ◽  
In Vitro Experiments ◽  
Mri Contrast ◽  
In Vivo Experiments ◽  
Contrast Agent Injection

The purpose of this study is to establish the minimal injection doses of magnetic resonance imaging (MRI) contrast agents that can achieve optimized images while improving the safety of injectable MRI drugs. Gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) and ferucarbotran, commonly used in clinical practice, were selected and evaluated with in vitro and in vivo experiments. MRI was acquired using T1-weighted (T1W) and T2-weighted (T2W) sequences, and the results were quantitatively analyzed. For in vitro experiments, results showed that T1W and T2W images were optimal when Gd-DTPA-bisamide (2-oxoethyl) (Gd-DTPA-BMEA) and ferucarbotran were diluted to a volume percentage of 0.6% and 0.05%; all comparisons were significant differences in grayscale statistics using one-way analysis of variance (ANOVA). For in vivo experiments, the contrast agent with optimal concentration percentages determined from in vitro experiments were injected into mice with an injection volume of 100 μL, and the images of brain, heart, liver, and mesentery before and after injection were compared. The statistical results showed that the p values of both T1W and T2W were less than 0.001, which were statistically significant. Under safety considerations for MRI contrast agent injection, optimized MRI images could still be obtained after reducing the injection concentration, which can provide a reference for the safety concentrations of MRI contrast agent injection in the future.

Albumin-bound MRI contrast agents: the dilemma of the rotational correlation time

2001 ◽  
Vol 12 (2-3) ◽  
pp. 135-140 ◽  
Author(s):  
Luce Vander Elst ◽  
Sophie Laurent ◽  
Helene Masaka Bintoma ◽  
Robert N. Muller
Keyword(s):  
Contrast Agents ◽  
Correlation Time ◽  
Rotational Correlation Time ◽  
Mri Contrast Agents ◽  
Mri Contrast ◽  
Rotational Correlation

scholarly journals High-speed high-resolution laser diode-based photoacoustic microscopy for in vivo microvasculature imaging

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiufeng Li ◽  
Victor T C Tsang ◽  
Lei Kang ◽  
Yan Zhang ◽  
Terence T W Wong
Keyword(s):  
High Resolution ◽  
High Speed ◽  
High Performance ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Cost Effective ◽  
High Signal ◽  
Photoacoustic Microscopy ◽  
Mouse Ear

AbstractLaser diodes (LDs) have been considered as cost-effective and compact excitation sources to overcome the requirement of costly and bulky pulsed laser sources that are commonly used in photoacoustic microscopy (PAM). However, the spatial resolution and/or imaging speed of previously reported LD-based PAM systems have not been optimized simultaneously. In this paper, we developed a high-speed and high-resolution LD-based PAM system using a continuous wave LD, operating at a pulsed mode, with a repetition rate of 30 kHz, as an excitation source. A hybrid scanning mechanism that synchronizes a one-dimensional galvanometer mirror and a two-dimensional motorized stage is applied to achieve a fast imaging capability without signal averaging due to the high signal-to-noise ratio. By optimizing the optical system, a high lateral resolution of 4.8 μm has been achieved. In vivo microvasculature imaging of a mouse ear has been demonstrated to show the high performance of our LD-based PAM system.

Sign in / Sign up

Export Citation Format

Share Document