scholarly journals Non‐negative least squares computation for in vivo myelin mapping using simulated multi‐echo spin‐echo T 2 decay data

2020 ◽  
Vol 33 (12) ◽  
Author(s):  
V. Wiggermann ◽  
I.M. Vavasour ◽  
S.H. Kolind ◽  
A.L. MacKay ◽  
G. Helms ◽  
...  
Keyword(s):  
Least Squares ◽  
Spin Echo ◽  
Decay Data

scholarly journals Non-negative least squares computation for in vivo myelin mapping using simulated multi-echo spin-echo T2 decay data

2020 ◽  
Author(s):  
Vanessa Wiggermann ◽  
Irene Vavasour ◽  
Shannon Kolind ◽  
Alex MacKay ◽  
Gunther Helms ◽  
...  
Keyword(s):  
Least Squares ◽  
Signal To Noise Ratio ◽  
Spin Echo ◽  
Signal Transmission ◽  
Geometric Mean ◽  
Magnetization Vector ◽  
Extracellular Water ◽  
Distribution Grid ◽  
Water Fraction

Multi-compartment T2-mapping has gained particular relevance for the study of myelin water in brain. As a facilitator of rapid saltatory axonal signal transmission, myelin is a cornerstone indicator of white matter development and function. Regularized non-negative least squares fitting of multi-echo T2 data has been widely employed for the computation of the myelin water fraction (MWF) and the obtained MWF maps have been histopathologically validated. MWF measurements depend upon the quality of the data acquisition, B1+-homogeneity and a range of fitting parameters. In this special issue article, we discuss the relevance of these factors for the accurate computation of multi-compartment T2 and MWF maps. We generated multi-echo spin-echo T2 decay curves following the approach of CarrPurcell-Meiboom-Gill for various myelin concentrations and myelin T2 scenarios by simulating the evolution of the magnetization vector between echoes based on the Bloch equations. We demonstrated that noise and imperfect refocusing flip angles yield systematic underestimations in MWF and intra-/extracellular water geometric mean (gm) T2. MWF estimates were more stable than myelin water gmT2 time across different settings of the T2 analysis. We observed that the lower limit of the T2 distribution grid should be slightly shorter than TE1. Both TE1 and the acquisition echo spacing also have to be sufficiently short to capture the rapidly decaying myelin water T2 signal. Among all parameters of interest, the estimated MWF and intra-/extracellular water gmT2 differed by approximately 0.13-4 percentage points and 3-4 ms, respectively, from the true values, with larger deviations observed in the presence of greater B1+-inhomogeneities and at lower signal-to-noise ratio. Tailoring acquisition strategies may allow to better characterize the T2 distribution, including the myelin water, in vivo.

The effect of microvascular obstruction on the myocardial microstructure: a diffusion tensor imaging study

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
A Das ◽  
K Kelly ◽  
M Aldred ◽  
I Teh ◽  
CK Stoeck ◽  
...  
Keyword(s):  
Microvascular Obstruction ◽  
Diffusion Tensor ◽  
Spin Echo ◽  
Mean Diffusivity ◽  
Imaging Study ◽  
Free Breathing ◽  
Helix Angle ◽  
Acquisition Time ◽  
Heart Research

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Heart Research UK Background Diffusion tensor cardiac magnetic resonance (DT-CMR) imaging allows for characterising myocardial microstructure in-vivo using mean diffusivity (MD), fractional anisotropy (FA), secondary eigenvector angle (E2A) and helix angle (HA) maps. Following myocardial infarction (MI), alterations in MD, FA and HA proportions have previously been reported. E2A depicts the contractile state of myocardial sheetlets, however the behaviour of E2A in infarct segments, and all DTI markers in areas of microvascular obstruction (MVO) is also not fully understood.  Purpose We performed spin echo DTI in patients following ST-elevation MI (STEMI) in order to investigate acute changes in DTI parameters in remote and infarct segments both with and without MVO. Method Twenty STEMI patients (16 men, 4 women, mean age 59) had acute (5 ± 2d) 3T CMR scans. CMR protocol included: second order motion compensated (M012) free-breathing spin echo DTI (3 slices, 18 diffusion directions at b-values 100s/mm2[3], 200s/mm2[3] and 500s/mm2[12], reconstructed resolution was 1.66x1.66x8mm); cine and late gadolinium enhancement (LGE) imaging. Average MD, FA, E2A HA parameters were calculated on a  16 AHA segmental level. HA maps were described by dividing values into left-handed HA (LHM, -90° < HA < -30°), circumferential HA (CM, -30° < HA < 30°), and right-handed HA (RHM, 30° < HA < 90°) and reported as relative proportions. Segments were defined as infarct (positive for LGE) and remote (opposite to the infarct).  Results DTI acquisition was successful in all patients (acquisition time 13 ± 5mins). Ten patients had evidence of MVO on LGE images. MD was significantly higher in infarct regions in comparison to remote; MVO-ve infarct segments had significantly higher MD than MVO + ve infarct segments (MD remote= 1.46 ± 0.12x10-3mm2/s, MD MVO + ve = 1.59 ± 0.12x10-3mm2/s, MD MVO-ve  = 1.75 ± 0.12x10-3mm2/s, ANOVA p < 0.01). FA was reduced in infarct segments in comparison to remote; MVO-ve infarct segments had significantly lower FA than MVO + ve infarct segments (FAremote= 0.37 ± 0.02, FA MVO + ve = 0.31 ± 0.02 x 10-3mm2/s, MD MVO-ve =0.25 ± 0.02, ANOVA p < 0.01). E2A values were significantly lower in infarct segments compared to remote; MVO + ve infarct segments had significantly lower values than MVO-ve. (E2A remote= 57.4 ± 5.2°, E2A MVO-ve = 46.8 ± 2.5°, E2A MVO + ve = 36.8 ± 3.1°, ANOVA p < 0.001). RHM% (corresponding to subendocardium) was significantly lower in infarct segments compared to remote; MVO + ve infarct segments had significantly lower RHM% than MVO-ve. (RHM remote= 37 ± 3%, RHM RHM MVO-ve= 28 ± 7%, MVO + ve= 8 ± 5%, ANOVA p < 0.001). Conclusion The presence of MVO results in a decrease in MD and increase in FA in comparison to surrounding infarct segments. However, the reduction in E2A and right-handed myocytes on HA in infarct segments is further exacerbated by the presence of MVO. Further study is required to investigate the underlying mechanisms for such alterations in signal intensity. Abstract Figure. A case of transmural septal MI with MVO

scholarly journals Synthesis, quantum chemistry analysis and pre-clinical in vivo evalution of magnetic resonance imaging abilities of paramagnetic manganese complex with 2,3-dimercaptosuccinate (succimang)

2019 ◽  
pp. 133-143 ◽  
Author(s):  
W. Yu. Ussov ◽  
V. D. Filimonov ◽  
M. L. Belyanin ◽  
A. I. Bezlepkin ◽  
M. A. Lucic ◽  
...  
Keyword(s):  
Quantum Chemistry ◽  
Water Solution ◽  
Spin Echo ◽  
Dimercaptosuccinic Acid ◽  
Stable Complex ◽  
Stable Form ◽  
Modified Technique ◽  
Paramagnetic Contrast Agent ◽  
Imaging Properties

Aim of the study. We have carried out the synthesis of complex of Manganese(II) with dimercaptosuccinic acid (DMSA), applied the quantum chemistry analysis for evaluation of most stable form of the Mn- DMSA complex and studied it’s uptake and imaging properties in normal and tumoral tissues in veterinary patients (cats with tumors)Material and methods. The synthesis of the 2.3-dimercaptosuccinic acid (COOH-CHSH-CHSH-COOH) has been carried out using modified technique proposed by A.I. Busev [Busev A.I. 1972]. Using phantoms filled in with 0.05 mM – 16 mM solutions of the agent we quantified the R1 relaxivity. Imaging properties of the 0.5 M solution of the Mn-(DMSA)2 were evaluated when performing the  contrastenhanced studies in veterinary patients (cats with adenofibrous tumors and angiofibromas, nine animals) using T1-w spin-echo mode.Results. As result of quantum chemistry analysis it was shown that the most stable complex of Mn(II) with DMSA is the molecule Mn-(DMSA)2. The R1 relaxivity of the Mn-(DMSA)2 complex in the water solution was as high as 3.2 1/(mM*s). In normal control animals the Mn-(DMSA)2 provided highly intensive enhancement of renal parenchyma and mild enhancement of liver, spleen and bone marrow. In animals with tumors the Mn-(DMSA)2 enhanced the T1-w spin-echo images of angiofibromas and fibroadenomas in both peripheral (index of enhancement = 1.87 ± 0.09, p < 0.01) and central (index of enhancement = 1.59 ± 0.07, p < 0.01) parts of the tumor.Conclusion. The imaging properties of the Mn-(DMSA)2 make an argue for real possibility of production of new non-Gadolinium paramagnetic contrast agents specific to tumors. Further study of the Mn-(DMSA)2 complex as paramagnetic contrast agent is of interest and useul.

High Resolution NMR Spectroscopy on Whole-Body Imagers:Optimized Single-and Multi-Pulse Experiments in Vitro

1995 ◽  
Vol 50 (10) ◽  
pp. 942-948
Author(s):  
Fritz Schick
Keyword(s):  
Aqueous Solutions ◽  
Spin Echo ◽  
Single Pulse ◽  
Spin Systems ◽  
The Body ◽  
Coupling Constants ◽  
Whole Body ◽  
Receiver Coil

Abstract From 100 ml spherical glass bottles filled with aqueous solutions and suspended in a homogeneous magnetic field, NMR spectra with linewidths of about 0.7 Hz were achieved in single-pulse and multi-pulse spectra. A relatively wide receiver coil as the body coil or the standard head coil of the manufacturer were employed to acquire spectra after different non-localized pulse sequences. Examples of single-pulse spectra and double spin-echo spectra of aqueous solutions with lactate, citrate, or glucose are demonstrated and discussed. The fact that all experiments can be performed using well-defined pulse angles acting on the entire sample at the field strenght of the whole-body unit allows to determine the characteristics (e.g. chemical shift differences, coupling constants) of spin systems of biologically important molecules precisely, without need for additional spectrometers. Constant flip angles are advantageous for adequate theoretical analysis of spectra from coupled spin systems. The effects of a defined "misadjustment" of the transmitter on the spectra can be measured directly, whereas localized methods always yield a superposition of signals due to the distribution of flip angles inside the selected volume. In some cases, optimized sequence parameters for localized examinations in vivo can be derived numerically from the analyzed coupling data.

scholarly journals Correlations between Proton Nuclear Magnetic Resonance Imaging and Retrospective Histochemical Images in Experimental Cerebral Infarction

1985 ◽  
Vol 5 (2) ◽  
pp. 267-274 ◽  
Author(s):  
Hiroyuki Kato ◽  
Kyuya Kogure ◽  
Hitoshi Ohtomo ◽  
Muneshige Tobita ◽  
Shigeru Matsui ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
Proton Nuclear Magnetic Resonance ◽  
Nmr Imaging ◽  
Resonance Imaging ◽  
H Nmr ◽  
Experimental Cerebral Infarction ◽  
Nuclear Magnetic

Evaluation of ischemic brain injury in experimental cerebral infarction in gerbils and rats was performed by means of both proton nuclear magnetic resonance imaging ([1H]NMR-CT) and various histochemical analyses. In vivo nuclear magnetic resonance (NMR) imaging was carried out employing saturation recovery, inversion recovery, and spin echo pulse sequences. Spatial resolution of the images was excellent. The ischemic lesions were detected with a remarkable contrast in inversion recovery and spin echo images within a few hours after insult. Those changes in NMR images consistently corresponded with the various retrospective histochemical observations, especially with methods related to brain edema (K+ staining) rather than structural (enzymatic) studies. Calculated T1 and T2 relaxation times indicated the evolution of the edema state in the brain in situ. They correlated excellently with the retrospective water content measurement. As a result, detailed characterization of the edema state induced by cerebral ischemia was possible in vivo using [1H]NMR imaging.

Spin-echo methods for the determination of 31P transverse relaxation times of the ATP NMR signals in vivo

1994 ◽  
Vol 12 (1) ◽  
pp. 121-129 ◽  
Author(s):  
Klaus Straubinger ◽  
Wulf-Ingo Jung ◽  
Michael Bunse ◽  
Otto Lutz ◽  
Klaus Küper ◽  
...  
Keyword(s):  
Spin Echo ◽  
Relaxation Times ◽  
Transverse Relaxation ◽  
Nmr Signals

Quantitative in vivo T2 mapping using fast spin echo techniques – A linear correction procedure

NeuroImage ◽  
2017 ◽  
Vol 157 ◽  
pp. 476-485 ◽  
Author(s):  
Ulrike Nöth ◽  
Manoj Shrestha ◽  
Jan-Rüdiger Schüre ◽  
Ralf Deichmann
Keyword(s):  
Spin Echo ◽  
T2 Mapping ◽  
Fast Spin Echo ◽  
Correction Procedure ◽  
Linear Correction ◽  
Fast Spin

scholarly journals In vivo proton electron double resonance imaging of mice With fast spin echo pulse sequence

2011 ◽  
Vol 35 (2) ◽  
pp. 471-475 ◽  
Author(s):  
Ziqi Sun ◽  
Haihong Li ◽  
Sergey Petryakov ◽  
Alex Samouilov ◽  
Jay L. Zweier
Keyword(s):  
Pulse Sequence ◽  
Spin Echo ◽  
Double Resonance ◽  
Fast Spin Echo ◽  
Resonance Imaging ◽  
Echo Pulse ◽  
Fast Spin
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