Conjugate gradient (CG) method has been used previously to reconstruct double quantum-single quantum (DQ-SQ) spectra. However, satisfactory results can be obtained only when the spectra contain only narrow peaks, but not in the case when broad peaks are present. Compressed sensing technology can break the limit of the Nyquist acquisition theorem and reconstruct under-sampled data with high quality. The technology has been applied in the field of nuclear magnetic resonance (NMR). In this paper, we propose to use compressed sensing with iterative soft thresholding (IST) to reconstruct two-dimensional solid-state NMR spectra with broad peaks, such as the spectra obtained in ¹H DQ-SQ and ⁸⁷Rb multiple quantum-magic angle spinning (MQ-MAS) experiments. It was found that, with the IST method, compressed sensing technology could be used to reconstruct high-quality spectra containing broad peaks from under-sampled datasets.

Nuclear Magnetic Resonance (NMR) is one of the most powerful analytical tools nowadays, with wide applications in the fields of chemistry, biology and medicine. The spatial encoding ultrafast method proposed by Frydman et al. in 2002 greatly enhanced the sampling efficiency of multi-dimensional NMR spectroscopy. One problem with the Frydman’s method is that it is difficult to selectively detect multiple resonances at non-continuous discrete frequencies, due to the fast-switching bipolar gradients that are required for spatial encoding. In this study, we proposed a novel selective spatial encoding ultrafast method, aiming to solve two problems often encountered when utilizing the Frydman’s method in practical chemical and biological applications. The first problem is to detect weak signals in the presence of strong signals with limited dynamic range; and the second problem is to detect the signals of interests (e.g., peaks from labeled nuclei) exclusively with the rest of resonances in the background unexcited. The proposed method utilized a selective pulse to destroy the encoding process selectively, such that selective suppression of strong peaks or excitation of non-continuous discrete frequency points of interest could be achieved. We also showed that only the spectral peak selected by the selective pulse would remain if the selective inverse pulse was replaced by a hard inverse pulse. The feasibility and validity of this method were demonstrated by both theoretical analyses and experiments.

Pseudo-continuous arterial spin labeling (pCASL) is perfusion imaging technique that combines the advantages of continuous arterial spin labeling (CASL) and pulsed arterial spin labeling (PASL). In this study, we implemented a pCASL sequence on uMR560 1.5 T MRI systems developed by United Imaging Healthcare Cooperation. Experiments were performed to demonstrate the stability of the pCASL sequence implemented and the accuracy of perfusion quantification. The tagging efficiency was first measured through phantom experiments. In order to achieve the highest signal-to-noise ratio, post-labeling delay time and labeling distance were optimized empirically to be approximately 70 mm blow the imaging slab and 1 200 ms, respectively. Lastly, perfusion-weighted signal intensity and absolute cerebral blood flow (CBF) were measured from 12 normal volunteers using the pCASL sequence implemented, with satisfactory results obtained from 10 subjects. In summary, the pCASL sequence implemented on the uMR560 1.5 T MRI systems can be used for perfusion imaging on human brain, with reasonable stability and accuracy.

In compressed sensing magnetic resonance imaging (CS-MRI), the quality of reconstructed image is largely determined by the random undersampling matrix. It is a common practice to select the random undersampling matrix though computation of the point spread function (PSF) and the maximal artifacts possible. In this paper, we proposed to use two novel statistical parameters, mean value (MV) and standard deviation (SD), to guide the selection of random undersampling matrix. The two parameters evaluate the average amplitude and fluctuation of the possible artifacts, respectively. Experiments on mice brain and human brain were used to compare image quality of CS reconstructions of MRI data acquired with random undersampling matrices determined by different criteria. It was shown that reconstruction with MV had better performance when the sampling ratio is above four times of sparsity. It is concluded that better CS-MRI reconstruction quality can be achieved with reasonable selection of sampling ratio guided by prior knowledge of sparsity and MV as random undersampling matrix evaluation parameter.

Motions occurring during in vivo magnetic resonance spectroscopy acquisition limit the quality of the spectra and their diagnostic value. Subtraction-based spectral editing techniques, such as J-difference editing, are especially prone to motion artifacts, causing false peaks or incomplete elimination of the background. In this study, a retrospective motion correction post-processing method was introduced to analyze GABA-edited spectra acquired by a MEGA point-resolved spectroscopy (MEGA-PRESS) sequence. Head motion during each acquisition was detected and recorded by the residual water signal; the motion-corrupted data were identified and excluded prior to averaging. The gain in spectral quality by using the proposed method was analyzed using the LCModel program. The results showed that the proposed method is an effective way to discard acquisitions corrupted by motion, and to improve spectral quality.

When performing chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) on biological samples at high fields, nuclear Overhauser enhancement (NOE) effects may produce negative signals on the Z-spectra. The NOE-related signal intensity changes have the potential to become a new contrast mechanism. However, the presence of lipids signals within the same chemical shift range may affect the observation of true NOE effect-related signal changes. In this work, we first analyzed the influence of lipid signals on the NOE effects in tissues abundant in lipid via experiments on eggs. Similar experiments were then carried out on healthy rats and rats with brain tumors. The results showed that the presence of large lipid signals could cause pseudo NOE effects and degrade the accuracy of NOE contrast imaging.

The NMR system is one of the physical systems that can be used to realize quantum computation. However, NMR-based quantum computing could have many drawbacks with increasing qubit number. One of the underlying reasons is that the signal of pseudo-pure state decreases exponentially with increasing qubit number. Besides, the process required to prepare a pseudo-pure state becomes more complicated as the spin system gets larger. Furthermore, the pseudo-pure state in NMR system is in fact a mixed state, making it difficult to realize quantum entanglement. In this paper, we used parahydrogen induced polarization (PHIP) technique to prepare a genuine pure state for NMR quantum computation with significantly enhanced signal intensity. The initial state was applied to implement a two-qubit Deutsch-Jozsa algorithm and a three-qubit Deutsch-like algorithm.

Wistar rats were intragastrically administered with different doses (0, 2, 5 g/kg body weight) of haematitum. ¹H NMR-based metabonomic techniques were used to analyze the metabolic profiles of the serum samples collected from the treated rats. Significant treatment-related changes were observed for the levels of β-hydroxybutyate, acetate, acetone, choline, glycerophosphorylcholine, glucose, lactate, low density lipoprotein, very low density lipoprotein and lipids. Such biochemical changes indicated that haematitum treatment at the dose of 2 or 5 g/kg body weight gave rise to reactive oxygen species (ROS) and caused peroxidation damage. It is concluded that haematitum treatment affects glucose, lipid and energy metabolism in rats.

DAST crystal (4-N, N-dimethylamino-4’-N’-methyl-stilbazolium tosylate crystal) shows electro-optical effect, and has excellent properties for second-order nonlinear optics. It can be used for wave radiation and detection from infrared to terahertz range. In this study, the molecular structure and purity of DAST crystal were analyzed by liquid-state NMR spectroscopy (i.e., ¹H NMR, ¹³C NMR, ¹H-¹H COSY, HSQC and HMBC) using CD₃OD and DMSO-d₆ as solvents. It was observed that DAST tended to exist in the form of ion pair in CD₃OD solution, while in the form of dissociative state in DMSO-d₆ solution. This could be due to solvent-dependent redistribution of electron cloud in the conjugated structure and movement of the framework.

The distribution of metabolites in the root bark of tree peony from different root parts was systematically analyzed using the combination of NMR and HPLC-MS for the first time. A total of 16 metabolites from their methanol extracts were simultaneously identified and quantified, including 1 primary metabolite (sucrose) and 15 secondary ones such as 4 acetophenones, 6 phenolics, 2 monoterpene glycosides, 1 flavonoid and 2 unsaturated fatty acids. The quantitative data indicated that there are the higher levels of acetophenones and sucrose, and the lower contents of phenolics, monoterpene glycosides, flavonoids and unsaturated fatty acids in the tree peony roots. NMR-based metabolomics revealed that the metabolite compositions were found to be different among the three root parts. The increasing levels of acetophenones and decreasing level of sucrose were observed in second lateral root, the first lateral and axial root in order. The axial roots have higher quality than the lateral roots in tree peony due to the accumulation of bioactive secondary metabolites associated with plant physiology. These findings provided important scientific evidence for grading the root bark of tree peony on the general market.

Time-domain nuclear magnetic resonance (TD-NMR) technology may provide a new method to study water absorption in wood-based panels. We measured changes of free induction decay (FID) signal of water in plywood, particle board and medium density fiberboard after a 24-hour soaking process, and the results were correlated to water contents calculated with the traditional weighing method. The amount of water absorption was plywood > particleboard > medium density fiberboard. The state of water in the panels was analyzed by spin-spin relaxation time (T₂) measurements. The result suggested that NMR is an effective tool to study the relationship between wood-based panels and water.

¹H spin-spin relaxation time (T₂) of water in 5 species of wood was measured by nuclear magnetic resonance (NMR) spectroscopy at room temperature and -3℃, which is thought to be related to the anatomical structure of the wood. The bound water content within swollen cell wall was determined by comparison of the inversion peak area before and after frozen treatment: Pinus sylvestris 38.3%, Cunninghamia lanceolata 38.5%, Populus sp. 36.0%, Fraxinus excelsior L. 35.6% and Ochroma pyramidale 47.6%. The bound water contents determined by NMR spectroscopy were apparently higher than those obtained by the conventional extrapolation methods, but similar to the results obtained by the solute exclusion method, porous plate method, centrifugal dewatering method. It is concluded that NMR may provide a rapid and non-destructive way to determine bound water content in wood.

The content and distribution of water in wood affect its performance. So far, most technologies to measure water content/distribution can only be applied to small wood samples. A method to measure the water content inside large timber is urgently needed, given that information on water content/distribution inside the harvested timber is often required before the timber can be processed to products. In this work, a mini cylindrical NMR sensor (i.e., 28 mm in diameter and 60 mm in length) for measuring water content inside large timber was designed. The sensitive volume is a coaxial ring just outside of the sensor. For measurement, the sensor needs to be placed inside a hole drilled on the timber, which has a similar diameter with the sensor. By moving the sensor around the wall of the hole, the NMR parameters of the timber could be measured. Preliminary experimental results showed that the sensor can detect signals from both free water and the bound water in large timber, and such signals can be used to calculate relative water contents.

For conventional reservoir, NMR is an effective technology that can be used to evaluate petrophysics and pore structure, distribution and saturation of pore fluid rapidly, nondestructively and economically. Applying NMR technologies to evaluate shale reservoir, however, often encounters problems such as low resolution and inapplicable interpretation and evaluation models, due to reservoir characteristics such as nanoscale pore, complex mineral composition, complex pore structure, high organic content, ultralow permeability, influence of internal field gradients and restricted diffusion et al. In this paper, we reviewed recent progresses in NMR technologies for shale oil and gas exploration and exploitation, and related data analysis methods. Special attention was given to areas such as improvement of NMR detection resolution and novel evaluation models for pore structure, rock physical property, and pore fluid distribution and recognition. Two areas needed further research are identified: relaxation mechanisms inside nano-pore and improving pore scale resolution of D-T₂. Petrophysics evaluation model and pore fluid evaluation model also need to be further optimized.

Diffusion ordered NMR spectroscopy (DOSY), sometimes also known as chromatographic NMR (CNMR), is a powerful tool for analyzing complex mixture. However, it is often difficult to distinguish components having similar molecular properties using only the diffusion characteristics. A practical way to solve this problem is adding some matrices, such as silica gel or polymers into magic angle spinning rotor or NMR tube, as the virtual stationary phase (VSP), to increase the difference in diffusion rate among different components. Matrix aided CNMR has been shown to have improved discriminating capability when analyzing complex mixtures. In this paper, recent progresses in the field of matrixed CNMR were reviewed.

Since the first generation ultra high field MRI systems were installed around 1990, ultra high field MRI has become one of the hottest research areas in the international community of magnetic resonance in medicine, due to the benefits of higher signal-to-noise ratio (SNR), better contrast, stronger blood oxygenation level dependent (BOLD) effect and increased spectral dispersion. In this review, the structure of latest 7.0 T whole body MRI system is briefly introduced, and the research progresses of ultra high field MRI and its future in medicine, neuroscience and cognitive science are also discussed.