NMR diffusion measurements have been undergoing continuous theoretical and practical development for more than four decades leading to more robust and accurate measurements and the ability to extract increasingly diverse information. Concomitant with this development has been applications ranging across ever more areas of science ranging from physical chemistry to clinical medicine. NMR diffusion measurements can provide information on not only the translational dynamics of a species but also on the local geometrical structures which influence translational motion, when used for the latter case such measurements are often referred to as q-space imaging. This review focuses on some of the significant developments in this area over the last decade.

Over the past decades, Magnetic Resonance Imaging (MRI) has evolved into a modality that offers perfusion imaging in addition to anatomy. Two principal methods of MR perfusion imaging exist: Dynamic Susceptibility Contrast (DSC) and Arterial Spin Labeling (ASL). DSC has been applied more widely than ASL; however, complete noninvasive assessment is only attained by using ASL. There are numerous variants of ASL, including CASL (continuous arterial spin labeling), EPISTAR (echo planar imaging and signal targeting with alternating radiofrequency), PICORE (proximal inversion with a control for off-resonance effects) and FAIR (flow-sensitive alternating inversion recovery). This review aims to provide a comprehensive overview of FAIR technique, including theoretical background and implementations, in particular the T₁ method for FAIR quantification. The problems and pitfalls involved in the quantification model revisited. Finally, a brief summary of applications is presented.

We developed a “Fluid Component Decomposition”method for fast NMR CPMG data inversion. This method assumes that fluids, either in bulk form or saturated in porous media, have certain predetermined functional shapes, which can be predetermined T₂ or T₁ distributions for 1D NMR inverse Laplace transform problem, predetermined (D, T₂) or (T₁, T₂) distributions for 2D NMR inverse Laplace transform problem, or predetermined (D, T₂, T₁) distributions for 3D NMR inverse Laplace transform problem. These predetermined shapes can be Gaussian, Bspline, or any functions predetermined experimentally or empirically.  This approach significantly reduces the computation time for NMR data inversion especially for multi-dimensional data sets from oil well measurements, without sacrificing the smoothness and accuracy of the inverted distributions.  Such method has a new application as a solution constraint for a group of NMR data with sequential well depths where spurious signals frequently result in dissimilar T₂ distributions for the same rock type.  The successful implementation of this method as a constraint of T₂ components inverted from T₂ echo trains at different depths involves nontrivial matrix manipulations and allows us to use T₂ distribution as a rock type indicator.

Strong and extremely homogeneous and stable static magnetic fields are usually required for high-resolution NMR. However, large inhomogeneity and drift of the magnetic fields exist in the resistive and hybrid magnets which can provide much higher magnetic fields than the superconducting counterpart. On the other hand, the susceptibility gradients and physiological motions in in vivo studies produce inhomogeneous and unstable magnetic fields. Therefore, the inhomogeneous and instable magnetic fields in the non-ideal condition are unavoidable and can hardly be eliminated by conventional methods such as shimming and locking. Some approaches had been proposed to obtain high-resolution NMR spectra in the inhomogeneous and instable field, such as intermolecular zero quantum coherences (iZQCs), spatially encoding single-scan scheme and deconvolution. In the paper, these four methods were discussed.

Resting state functional connectivity has been studied extensively by functional magnetic resonance imaging (fMRI) approach. Synchronic low frequency fluctuations in resting state fMRI data are analyzed by different methods to measure functional connectivity between different brain regions. The most studied resting state brain network is the default mode network which might subserve basic brain functions related to consciousness. In this paper, the fMRI approach to study resting state brain functional connectivity is reviewed. The data analysis methods and the characteristics of the resting state networks are summarized. The relationship between the resting state networks and anatomical connectivity defined by white matter tracts is discussed.

Energy metabolism and neurotransmission are fundamental to all brain functions and their abnormalities are invariably the causes of various neurogenic or psychotic diseases. Therefore, understanding energy metabolism and neurotransmission has long been one of the major topics in the brain research, particularly essential for revealing the mechanism of brain functions. While it is well-known that glucose is the main energy source of the brain, it has been difficult to quantitatively measure the metabolic kinetics and the neurotransmission in vivo. Owing to their unique advantages, nuclear magnetic resonance (NMR) method has quickly emerged as one type of the most important tool in the field. In this paper, the principle and techniques of the relevant NMR methods as well as their applications in the studies of metabolic kinetics and neurotransmission are comprehensively reviewed.

Bio-activated MRI contrast agents are often called “enzyme activated”, “bio-responsive” or “smart” contrast agents because they respond, specifically, to enzymatic activity, metal ion concentration, pH et al factors, respectively. Recent progress in the development of bioactivated MRI contrast agents is reviewed with the emphasis on the design principle of contrast generation based on the analysis of the structure, properties and functions of these compounds.

The aim of this study is to explore the distinct cerebral activation with 10 Hz-modulated wave (MW) stimulation during lowlevel laser acupuncture. Functional magnetic resonance imaging (fMRI) studies have been performed to investigate the possible mechanism during laser acupuncture stimulation at the left foot's yongquan (K1) acupoint. It was found that the MW stimulation aroused the significant activations within the precentral gyrus of right frontal lobe, the right superior frontal gyrus, the precentral gyrus of left frontal lobe, the postcentral gyrus of left parietal lobe, the left inferior parietal lobule, the cerebellar lingua of left anterior lobe, the left parahippocampal gyrus, and left culmen. However, placebo stimulation did not show any activation. Most activated areas were involved with the functions of memory, attention, and selfconsciousness. The results show the cerebral hemodynamic response to the MW laser acupuncture stimulation mode the mechanism of which is not merely information processing based upon afferent sensation, but also the hemodynamic property that may be altered with the change of the external stimulation.

Echo-planar imaging suffers from susceptibility-induced distortion in the frontal lobe, temporal lobe and brain stem regions. To correct for the distortion, recently we proposed an easy-implemented and effective method called model-based point spread function (PSF) method. This study aimed to investigate the effectiveness of distortion correction from the perspective of fiber tracking. The evaluation was carried out by applying the modelbased PSF method on diffusion spectrum imaging (DSI) dataset and comparing the number of cingulum tracts generated from the distorted DSI dataset and the corrected DSI dataset. An index representing the effectiveness of distortion correction was defined as: r=(N_c-N_d)/(N_c+N_d), where N_c and N_d were, respectively, the number of tracts generated from DSI dataset after distortion correction and that without correction. For the left and right cingulum bundles, the ratios of the effectiveness of distortion correction were 0.424±0.452 (mean±SD) and 0.343±0.452, respectively. In addition, the ratios of both cingulum bundles were significantly greater than zero, indicating that the tracking results after distortion correction were better than those without correction. In conclusion, our results suggest that application of distortion correction on DSI dataset using the model-based PSF method can significantly improve the fiber tracking results.

A study of nuclear magnetic resonance and imaging (NMR/MRI) of optically pumped hyperpolarized 3He using high Tc superconducting quantum interference device (SQUID) in microtesla fields was reported. Hyperpolarized ³He was obtained by pumping optical cell containing ³He, N₂, ⁴He and a few grams of Rb metal using a circularly polarized laser. In the characterization of ³He the precession spins of ³He were coupled to the SQUID magnetometer by a flux transformer. The SQUID and was designed within a superconducting Bi₂Sr₂Ca₂Cu₃O_y vessel to avoid environmental noises. The NMR signal using the flux transformer shows an enhancement in signal-to-noise ratio over that directly measured by the SQUID magnetometer. The SQUID-detected NMR/MRI using hyperpolarized ³He can be of interest for lung imaging in ultralow magnetic fields.

Within an advisable measurement time, the signal-to-noise ratio (SNR) is a major limitation of nuclear magnetic resonance microscopy at the spatial resolution of micrometers level.  In previous reports, computer simulations showed the “Diffusion Enhancement of Signal and Resolution” (DESIRE) effect may provide potential signal enhancement of one order in one-dimensional case.  However, the timeconsuming calculations such as iterative matrix multiplications and finite-differential (FD) methods were utilized for simulating the external magnetic fields and diffusion propagations.  In this work, we proposed to use the Shinnar-LeRoux (SLR) algorithm and convolution based diffusion method to accelerate the simulations.  Therefore, extensive simulations can be conducted for optimization of pulse sequence.  Considering the enhance rate and effective resolution in one dimensional DESIRE experiment, the simulated results indicated the pulse shape of Sinc3 with optimal parameters could achieve superior performance under practical experimental settings.

Magnetic resonance imaging (MRI) now plays a significant role in clinical medical diagnosis. How to increase the image contrast has been of crucial importance in the field of MRI. Traditionally， contrast is generated by the differences in the magnetic resonance properties between different positions. However， when these differences are small， the desired contrast may not be achievable even if a long evolution time is used. Radiation damping is one of proposed approaches that may give a solution to this problem. Our previously published results indicate that radiation damping can induce a large contrast for small frequency differences even in a short period of time. Nevertheless， radiation damping requires a highly sensitive RF coil and must meet other conditions for it to be practically useful. The paper explains how to generate radiation damping by using a purposefully designed external circuit and how to control the spin dynamics so that the contrast is increased and a novel type of MRI is introduced.

Neuroanatomical connection is crucial to the understanding of brain function. The language anatomical model proposed that Broca’s area located in the inferior frontal lobe and Wernicke’s area located in the superior temporal gyrus, both were connected through the arcuate fasciculus, which functions in fast, automatic word repetition. Furthermore, the supramarginal gyrus has been highlighted the importance for phonological processing in recent neuroimaging studies. Diffusion MRI is a non-invasive technique for in vivo measurement of microstructural properties of brain white matter. Integrated with fiber tractography algorithm, there can be visualized the three-dimensional (3D) pathways of white matter tracts. The aim of this study is to visualize the corticocortical connection of language areas in the human brain via high angular resolution diffusion imaging and tractography.

Chaotic spin dynamics arising from the joint action of radiation damping and the distant dipolar field are shown to generate irreproducible measurements in popular high-field gradient magnetic resonance experiments, a phenomenon more general than previously thought. A periodic control scheme based on radio-frequency perturbations is developed that decreases the leading Lyapunov exponent and reduces observed fluctuations to within intrinsic spectrometer instability. General guidelines for designing and integrating such schemes into existing pulse sequences to suppress spin chaos are discussed.

We attempted to prepare CsH₂PO₄ (CDP) and CsH₅(PO₄)₂ (CPDP), compounds known to be promising solid acid electrolytes for fuel cells. The CDP and CPDP mixture was crystallized from an aqueous solution of Cs₂CO₃∶H₃PO₄, in a molar ratio of 1∶4, while the mixture of CDP and Cs₂HPO₄·1.5H₂O (H-DCHP) was obtained from the aqueous solution in a molar ratio of 1∶2. Methanol washing was most effective in separating the CDP from the mixture. The ¹³³Cs and ³¹P MAS NMR spectra of CDP, CPDP, and H-DCHP, and the ¹H MAS NMR spectra of CPDP and H-DCHP were reported for the first time and the peaks corresponding to each compound assigned. Herein, we demonstrated multinuclear SS-NMR to be a very useful tool to control the quality of the syntheses of solid acid electrolytes by identification of the electrolytes synthesized and the by-products produced in the process of the syntheses.

More and more evidence indicates that the information on protein dynamics extracted from the “traditional” measurement of longitudinal, transverse and NOE cross relaxation rates is insufficient for a full description of the complex motions a protein may have, such as chemical and conformational exchanges or the interaction-induced dynamics changes. Extra dynamic information can be obtained from relaxation mechanism involving multi-quantum coherences. In this article, the effective relaxation rates of mixed zero- and double-quantum coherences of CαH systems in two proteins (one with ¹³C labeled and one natural abundant) have been measured with a modified pulse sequence. The trend of the relaxation rates with the change of the intervals between π pulses in CPMG period indicates the ubiquitous existence of exchange in the proteins. The temperature dependence of protein dynamics is shown with the measurement of effective transverse relaxation rates for three different temperatures. It is also found that the number of exchanging sites varies with type and location of the residue in a protein. Furthermore, quantitative analysis indicates that the effect of exchange on relaxation rate suggests that the presence of multi-site exchanges is common feature for proteins in solution, signifying that the exchange model currently used in description of protein exchange dynamics needs to be improved.

In this article, the phase separation of linear PNIPAM and gel in water/methanol binary solvents was studied by the measurements of NMR spectra and relaxation times. It was found that ¹H NMR spectrum of PNIPAM, relaxation times of solvents changed dramatically when phase transition occurred. When PNIPAM gel in binary solvents was heated above the LCST only part of the solvents was expelled from the polymer networks and the other part remained inside the polymer networks, resulting in two distinct type of solution. Comparison the compositions of two distinct solution provides a convenient, direct means of characterizing the preferential adsorption of solvent on polymer. On the contrary, there was no obviously change of the solution peaks from ¹H NMR spectrum as linear PNIPAM dissolved in water/methanol binary solvents.

The molecular mechanisms that regulate the asymmetric partitioning of the nitroxide spin-labeled lipids, 5-PC and 16-PC, in the coexistence of DLPC-rich liquid-disordered and DPPC-rich gel phases are investigated. In the two-phase coexistence region, our results of the ESR spectra show that the partition of 16-PC into the two phases strictly follows the “lever rule” as a function of composition by fitting the spectra with two conjugated phases. On the other hand, 5-PC spin label does not partition equally in the same region. This indicates the asymmetric partitioning of lipid spin labels that is due to the steric environment at which the spin label is attached. The mechanism of the asymmetric partitioning is rationalized in terms of the local free-surface-area of spin label, which is demonstrated the major factor that affects the partitioning of spin labels into the coexisting phases. The analysis result from the stochastic spectral simulations unravels the complex mixing behaviors and molecular incorporation of the labeled molecules in the membrane phases, irrespective of their asymmetric partition.