Spin-spin Relaxation Time Constant Research Articles

Biomarkers of Cartilage Composition.

Magnetic resonance imaging (MRI) has significantly advanced the understanding of osteoarthritis (OA) because it enables visualization of noncalcified tissues. Cartilage is avascular and nurtured by diffusion, so it has a very low turnover and limited capabilities of repair. Consequently, prevention of structural and detection of premorphological damage is key in maintaining cartilage health. The integrity of cartilage composition and ultrastructure determines its mechanical properties but is not accessible to morphological imaging. Therefore, various techniques of compositional MRI with and without use of intravenous contrast medium have been developed. Spin-spin relaxation time (T2) and spin-lattice relaxation time constant in rotating frame (T1rho) mapping, the most studied cartilage biomarkers, were included in the recent standardization effort by the Quantitative Imaging Biomarkers Alliance (QIBA) that aims to make compositional MRI of cartilage clinically feasible and comparable. Additional techniques that are less frequently used include ultrashort echo time with T2*, delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), glycosaminoglycan concentration by chemical exchange-dependent saturation transfer (gagCEST), sodium imaging, and diffusion-weighted MRI.

Materials Technology for Heterogeneous Polymer Systems : Part II. Investigation of Motional Heterogeneity in Rubber Vulcanizates

For rubber vulcanizates or crosslinked rubbers, inherent characteristics of rubber elasticity are well known to be mainly controlled by the change in conformational entropy under deformation, causing constrained molecular mobility of rubbery network chains. In this part II of special lecture, 1H-pulsed NMR method is applied to observe the motional heterogeneity in the crosslinked rubbers, related to effects of crosslink density and incorporation of reinforcing carbon black fillers on the tensile failure behaviors under various conditions. Furthermore, as for analysis of thermo-oxidative aging behaviors for the crosslinked rubbers, the relationships between the breaking stretch ratio in tensile measurements, λb, and NMR relaxation properties such as spin-spin relaxation time, T 2, and residual dipolar coupling constant , D res, were discussed to predict the failure properties of small pieces sampled from engineering rubber parts, for which tensile tests could not be easily performed.

Evaluation of fluorine-19 magnetic resonance imaging of the lungs using octafluorocyclobutane in a rat model.

PurposeTo test octafluorocyclobutane (OFCB) as an inhalation contrast agent for fluorine‐19 MRI of the lung, and to compare the image quality of OFCB scans with perfluoropropane (PFP) scansTheory and MethodsAfter normalizing for the number of signal averages, a theoretical comparison between the OFCB signal‐to‐noise ratio (SNR) and PFP SNR predicted the average SNR advantage of 90% using OFCB during gradient echo imaging. The OFCB relaxometry was conducted using single‐voxel spectroscopy and spin‐echo imaging. A comparison of OFCB and PFP SNRs was performed in vitro and in vivo. Five healthy Sprague‐Dawley rats were imaged during single breath‐hold and continuous breathing using a Philips Achieva 3.0T MRI scanner (Philips, Andover, MA). The scan time was constant for both gases. Statistical comparison between PFP and OFCB scans was conducted using a paired t test and by calculating the Bayes factor.ResultsSpin‐lattice (T1) and effective spin‐spin (T2∗) relaxation time constants of the pure OFCB gas were determined as 28.5 ± 1.2 ms and 10.5 ± 1.8 ms, respectively. Mixing with 21% of oxygen decreased T1 by 30% and T2∗ by 20%. The OFCB in vivo images showed 73% higher normalized SNR on average compared with images acquired using PFP. The statistical significance was shown by both paired t test and calculated Bayes factors. The experimental results agree with theoretical calculations within the error of the relaxation parameter measurements.ConclusionThe quality of the lung images acquired using OFCB was significantly better compared with PFP scans. The OFCB images had higher a SNR and were artifact‐free.

Optimising magnetic resonance sampling patterns for parametric characterisation

Sampling strategies are often central to experimental design. Choosing efficiently which data to acquire can improve the estimation of parameters and reduce the acquisition time. This work is focused on designing optimal sampling patterns for Nuclear Magnetic Resonance (NMR) applications, illustrated with respect to the best estimate of the parameters characterising a lognormal distribution. Lognormal distributions are commonly used as fitting models for distributions of spin-lattice relaxation time constants, spin-spin relaxation time constants and diffusion coefficients. A method for optimising the choice of points to be sampled is presented which is based on the Cramér–Rao Lower Bound (CRLB) theory. The method’s capabilities are demonstrated experimentally by applying it to the problem of estimating the emulsion droplet size distribution from a pulsed field gradient (PFG) NMR diffusion experiment. A difference of <5% is observed between the predictions of CRLB theory and the PFG NMR experimental results. It is shown that CLRB theory is stable down to signal-to-noise ratios of ∼10. A sensitivity analysis for the CRLB theory is also performed. The method of optimizing sampling patterns is easily adapted to distributions other than lognormal and to other aspects of experimental design; case studies of optimising the sampling scheme for a fixed acquisition time and determining the potential for reduction in acquisition time for a fixed parameter estimation accuracy are presented. The experimental acquisition time is typically reduced by a factor of 3 using the proposed method compared to a constant gradient increment approach that would usually be used.

Optimal echo time for functional MRI of the infant brain identified in response to noxious stimulation.

PurposeBlood oxygen level dependent (BOLD) brain activity, measured using functional MRI (fMRI), is dependent on the echo time (TE) and the reversible spin–spin relaxation time constant ( T2*) that describes the decay of transverse magnetization. Use of the optimal TE during fMRI experiments allows maximal sensitivity to BOLD to be achieved. Reports that T2* values are longer in infants (due to higher water concentrations and lower lipid content) have led to the use of longer TEs during infant fMRI experiments; however, the optimal TE has not been established.MethodsIn this study, acute experimental mildly noxious stimuli were applied to the heel in 12 term infants (mean gestational age = 40 weeks, mean postnatal age = 3 days); and the percentage change in BOLD activity was calculated across a range of TEs, from 30 to 70 ms, at 3 Tesla. In addition, T2* maps of the whole brain were collected in seven infants.ResultsThe maximal change in BOLD occurred at a TE of 52 ms, and the average T2* across the whole brain was 99 ms.ConclusionA TE of approximately 50 ms is recommended for use in 3T fMRI investigations in term infants. Magn Reson Med 78:625–631, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Abstract 620: Water as a Universal Biosensor for Inflammation, Insulin Resistance and Dyslipidemia

Current proteomic strategies exploit the measurement of hundreds-to-thousands of potential biomarkers to establish profiles of disease risk. We propose an alternative strategy - inverse proteomics - which utilizes just one marker to monitor the status of many biomolecules all at once. Water is an attractive surveillance system, as it forms hydrogen bonds with virtually every protein, lipoprotein and metabolite in human blood. Here we show that the mobility of water in plasma and serum samples from apparently healthy human subjects correlates with known markers of inflammation, insulin resistance, dyslipidemia and possibly, oxidative stress. Water mobility is assessed in a six-minute experiment that requires no sample manipulations or chemical reactions. Rather, the spin-spin relaxation time constant (T 2 ) is measured non-invasively using benchtop time-domain nuclear magnetic resonance. The current discovery provides a framework for developing a simple blood test that could identify individuals with hidden risk for diabetes, atherosclerosis and Alzheimer’s disease.

Detection of Iron Nanoparticles using Nuclear Magnetic Resonance Relaxometry and Inverse Laplace Transform

Department of Bioindustrial Machinery Engineering College of Agriculture and Life Sciences, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si 561-756, Republic of Korea Received: November 14th, 2014; Revised: November 24th, 2014; Accepted: November 26th, 2014 Purpose: Rapid detection of bacteria is very important in agricultural and food industries to prevent many foodborne illnesses. The objective of this study was to develop a portable nuclear magnetic resonance (NMR)-based system to detect foodborne pathogens (E. coli). This study was focused on developing a method to detect low concentrations of magnetic nanoparticles using NMR techniques. Methods: NMR relaxometry was performed to examine the NMR properties of iron nanoparticle mixtures with different concentrations by using a 1 T permanent magnet magnetic resonance imaging system. Exponential curve fitting (ECF) and inverse Laplace transform (ILT) methods were used to estimate the NMR relaxation time constants, T1 and T2, of guar gum solutions with different iron nanoparticle concentrations (0, 10-3, 10-4, 10-5, 10-6, and 10-7 M). Results: The ECF and ILT methods did not show much difference in these values. Analysis of the NMR relaxation data showed that the ILT method is comparable to the classical ECF method and is more sensitive to the presence of iron nanoparticles. This study also showed that the spin-spin relaxation time constants acquired by a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence are more useful for determining the concentration of iron nanoparticle solutions comparwith the spin-lattice relaxation time constants acquired by an inversion recovery pulse sequence. Conclusions: We conclude that NMR relaxometry that utilizes CPMG pulse sequence and ILT analysis is more suitable for detecting foodborne pathogens bound to magnetic nanoparticles in agricultural and food products than using inversion recovery pulse sequence and ECF analysis.

Quantitative prediction of ischemic stroke tissue fate

Accurate prediction of ischemic tissue fate could aid clinical decision-making in the treatment of acute stroke. We investigated predictions of tissue fate for three (30-min, 60-min and permanent) stroke models in rats. Quantitative cerebral blood flow (CBF), apparent diffusion coefficient (ADC) and spin-spin relaxation time constant (T(2)) were acquired during the acute phase and at the end point followed by histological examination. Probability-of-infarct profiles based on ADC and CBF data were constructed using a training dataset. Probability-of-infarct maps were predicted using only acute stroke data from a separate experimental dataset, revealing the likelihood of future infarction. Performance measures of sensitivity and specificity showed accurate predictions. Sensitivities (mean +/- SD) for the 30-min, 60-min and permanent stroke were, respectively, 82 +/- 6%, 82 +/- 7%, and 86 +/- 4%, specificities were 83 +/- 5%, 86 +/- 5%, and 89 +/- 6%, and the areas under the receiver operating curve were 87 +/- 3%, 90 +/- 4%, and 93 +/- 3%. Importantly, to improve prediction accuracy, we took into account regional susceptibility to infarction. Spatial frequency-of-infarct maps were constructed and predictions were made by taking the weighted average of the probability-of-infarct map and spatial frequency-of-infarct map. The optimal weighting coefficient of spatial frequency-of-infarct was small (10%) for the permanent occlusion group but surprisingly large (40%) for the reperfusion groups, indicating that regional susceptibility of infarction was important for accurate prediction in reperfusion stroke. We concluded that the likelihood of cerebral infarction in rats can be accurately predicted and that accounting for regional susceptibility of infarct further improves prediction accuracy. Predictive models have the potential to provide a valuable quantitative framework for clinicians to consider different stroke treatment options.

MRI of great vessel morphology and function in Ehlers-Danlos syndrome type IV

The purpose of this study was to investigate whether large arteries in subjects with Ehlers-Danlos Syndrome Type IV (EDS IV) exhibit altered morphological and functional characteristics that might indicate the risk of complications. Subjects with EDS IV, an inherited disorder of type III collagen, have a significant lifetime risk of arterial rupture. Magnetic Resonance Imaging (MRI) of the aorta and carotid artery was used to measure diameter, wall thickness, pulse propagation velocity, and spin-spin relaxation time constant (T(2)) of the artery walls. These measurements were made and compared by a two-sided t-test in 17 subjects with EDS IV and in eight age and gender matched sibling controls. Additionally, Spearman correlation was computed between measurements and the average longevity of affected relatives. Comparing controls to 15 subjects with no known prior aortic complications, we found no differences in the diameters of the descending thoracic and abdominal aortas, but did find ascending aorta dilatation in two subjects (13%). We also found a trend in EDS IV subjects toward higher wall thicknesses after normalizing by body surface area for both the abdominal aorta (P=0.05) and the common carotid artery (P=0.07). Finally, we found a significant negative correlation (R= -0.82, P=0.02) between age-adjusted pulse propagation velocity and familial longevity. In conclusion, preliminary evidence suggests that elevated pulse propagation velocity, which indicates reduced vessel distensibility, may be a risk factor for complications of EDS IV. Ascending aorta dilatation and increased vessel wall thickness were also found in subjects with EDS IV and represent potential risk factors for future study.

STUDIES OF HARDNESS AND WATER MOBILITY OF COOKED WILD RICE USING NUCLEAR MAGNETIC RESONANCE

The changes in hardness and molecular mobility of water of cooked wild rice during 10 days storage were investigated in this study. Seven grades of wild rice were subjected to various degrees of soaking and cooking and were stored at 5C. Nuclear magnetic resonance (NMR) technique was employed to determine the free induction decay (FID) signals and spin-spin relaxation time constants (T 2 ) of protons, which was regarded as a measure of rotational molecular mobility of water in the samples. Multi-component behavior of FID signals was observed, based on which water molecules in the samples were classified into three fractions with different T 2 s. The hardness of the samples was assessed using a texture analyzer. All samples firmed over the storage period, which correlated well with the changes in NMR parameters. A multiple variable regression model was proposed to describe the relationships between firming and NMR parameters in the wild rice samples. The model demonstrates the possibility of using NMR parameters to assess and predict the firmness of the samples during storage.

Methacrylic acid polymerization. Traveling waves observed by nuclear magnetic resonance imaging

NMR imaging has been used to examine travelling waves of benzoyl peroxide initiated methacrylic acid polymerization. The polymer/monomer interface is sharply defined (<1.2 mm) and is characterized by an abrupt discontinuity in the NMR spin-spin relaxation time constant (T 2 ). The front velocity measured from a series of one-dimensional magnetization profiles is 0.61 cm/min. The polarizing magnetic field B 0 has little or no effect on the observed velocity