High-intensity focused ultrasound (HIFU) is a noninvasive thermal ablation therapy. Thermometry techniques with high precision and temporal resolution are needed to ensure the safety and effectiveness of HIFU. The magnetic resonance thermometry (MRT) technique based on proton resonance frequency shift (PRFS) shows good linearity with and high sensitivity to temperature change, and is frequently used in HIFU therapy. In practice, HIFU may have a potential danger of causing unwanted skin burns far away from the focus of ultrasound irradiation. It is therefore desirable to increase the spatial coverage of MRT measurements to include the skins. In this work, a fast three-dimensional (3D) MRT technique was developed based on an echo-shifted gradient-recalled sequence with controlled aliasing in volumetric parallel imaging. Phantom experiments were first used to calibrate the accuracy and precision of temperature measurements made by the proposed technique to those obtained by an optical fiber thermometer. Pork tissues were then scanned at room temperature to determine the precision of temperature measurements before and after imaging acceleration. The pork tissues were also scanned under the condition of HIFU heating to compare the accuracy of temperature measurements with or without imaging acceleration.

BLADE is the commercial name of a spin-echo imaging technique that uses periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) k-space trajectory. In this study, the efficiency of using BLADE to improve hippocampal imaging in mental patients was assessed. The hippocampi of 47 mental patients were imaged on a 3.0 T scanner along the oblique coronal orientation using the T₂WI TSE and T₂WI FLAIR sequences with or without the use of BLADE. The same four sequences were also used to scan a standard American College of Radiology (ACR) phantom according to the ACR standards. The hippocampal images were scored by two radiologists using a 5-point scale, in terms of motion artifact, pulsation artifact, perceptive coarseness and image quality. The outcomes were compared between the sequences by two-sample Wilcoxon tests. The images of the phantom were evaluated semi-quantitatively for high contrast spatial resolution (HCSR) and low contrast object detection detectability (LCD) by counting the number of hole arrays and spokes that could be detected. The results showed that, compared to the conventional sequences, the sequences combined with BLADE technique showed significantly reduced motion and pulsation artifacts (p<0.001), improved image quality (p<0.05), but increased the perceptive coarseness (p<0.001). In the phantom experiments, the use of BLADE greatly improved the LCD, but had little effects on the HCSR. Based on these results, the BLADE technique is recommended for hippocampal imaging in mental patients with low compliance with the guidance.

A classification method was developed to differentiate cognitive normal controls (CN), mild cognitive impairment (MCI) patients and Alzheimer's disease (AD) patients from the magnetic resonance (MR) image data. Three-dimensional (3D) local pattern transformation was used in the proposed method to obtain texture features, which were then fused with the conventional image features for the classification purposes. Region of interests (i.e., bilateral hippocampus, gray matter and white matter) were selected from the MR images of 46 CN, 61 MCI patients and 25 AD patients, from which the 3D local pattern transformation texture features and conventional image features were extracted, fused and used for classification with the support vector machine. It was demonstrated that the accuracy, sensitivity, specificity and area under the curve (AUC) were 88.73%, 78.00%, 95.7% and 0.886 5, respectively, for the fused texture feature/conventional image features in bilateral hippocampus of CN controls and AD patients. In comparison, the fused features in the gray matter gave an accuracy, sensitivity, specificity and AUC of 85.92%, 80.00%, 86.6% and 0.854 3, respectively. It is concluded that the texture features extracted from 3D local pattern transform in hippocampus could be used in conjunction with the conventional image features for better classification of the course of Alzheimer's disease.

In this paper, the use of software radio technology for signal reception in magnetic resonance imaging (MRI) was attempted. A radio frequency direct band-pass sampling method was proposed for signal reception in MRI. For this method, a digital demodulation algorithm was designed and implemented with System Generator, a design and development tool of digital signal processing (DSP) developed by the Xilinx company. At the same time, a digital down conversion (DDC) system was designed and tested to flexibly implement the DDC function. The validity of the proposed receiving method was confirmed by numerical simulations and experiments.

Nuclear magnetic resonance (NMR) spectroscopy is an important tool for studying the structures of molecules and materials. Mainly due to their high costs, the NMR spectrometers are often not available for teaching experiments. Teaching NMR experiments cannot be performed routinely and effectively also because that the students are not able to understand the principles underlying the operational steps without proper and adequate training. In this work, a virtual NMR spectrometer (VMRS1.0) for teaching experiments, which is based on numerical computational simulation technology and can be operated like a real spectrometer, is presented. With the VMRS1.0, the students can perform basic NMR experiments, including tuning, shimming, field lock, power adjustment for radio frequency, selecting samples, acquiring data, fast Fourier transform and spectrum processing (i.e., phase correction, integration, chemical shift correction, auto peak finding and J-coupling constant measurement). In addition to the routine one-dimensional NMR experiments, more complicated experiments such as decoupling, DEPT and HMQC can also be performed on the VMRS1.0. With the virtual NMR spectrometer developed, the students can practice their experimental skills and gain deeper understandings of the underlying principles in a more easy and cost-efficient way.

The reaction of photocatalytic methanol reforming in a real solid-liquid reaction environment was studied by in operando nuclear magnetic resonance (NMR) spectroscopy. Four liquid-state intermediate products were detected in the reaction systems investigated, including HOCH₂OH, CH₃OCH₂OH, HCOOH and HCOOCH₃. It was also demonstrated that the crystal types of TiO₂ catalysts had a strong influence on the production of the four intermediate products. And the contents of the four products increased with the increasing illumination time. Palladium (Pd) loading enhanced the production of CH₃OCH₂OH and HOCH₂OH by 2~3 orders of magnitude, but had little effects on the production of HCOOCH₃ and HCOOH.

During in-situ exploitation of the oil shale, the connectivity of the pore structure of the reservoir directly affects not only the flow behavior and heat transfer efficiency of the heat-carrying medium, but also the diffusion and flow behaviors of the oil and gas. In this study, the T₂ spectra of saturated water and bound water in samples from the Fushun oil shale were measured with low-field nuclear magnetic resonance at different final pyrolysis temperatures (23~650℃). NMR pore parameters, including T₂ cutoff value of movable fluid, bound fluid porosity, saturated fluid porosity and permeability, were analyzed. The evolution of pore connectivity of the oil shale with final pyrolysis temperature was studied quantitatively. The results demonstrated that final pyrolysis temperature affected the variations of pore connectivity and the permeability of oil shale. The increase of total porosity could be attributed mainly to the increments of movable fluid. These results indicated that increases in final pyrolysis temperature enhanced the permeability and transport of oil and gas, providing a basis for further understanding of the evolution of pore structure in oil shale in-situ pyrolysis.

An inclusion complex of naringenin (NAR) and β-cyclodextrin (βCD) was prepared with ultrasonication. Powder X-ray diffraction (XRD) and infrared absorption spectroscopy (IR) indicated that the inclusion complex formed had some new physical/chemical properties. ¹H NMR and ROESY spectroscopy revealed that the stable supramolecular inclusion complex was formed by having the benzene ring of NAR introduced into the big end of the βCD. The formation processes of NAR/βCD inclusion complex were also studied by quantum chemical calculations. It was revealed that enthalpy and hydrogen bonding weak interaction force were the driving forces behind the formation. The optimal inclusion mode obtained from energy gap and binding energy analyses were consistent with the most inclusive mode obtained from molecular docking analysis and the NMR results. These results were further confirmed by ONIOM calculation.

C₁₉-diterpenoid alkaloids have complex and diverse structures, posing great challenges for nuclear magnetic resonance (NMR)-based structural elucidation. Three C₁₉-diterpenoid alkaloids, including taronenine E (1), chasmaconitine (2) and vilmorisine (3), were isolated from the roots of Aconitum taronense Fletcher et Lauener, and analyzed by various NMR spectroscopy methods (i.e., ¹H and ¹³C NMR, DEPT, ¹H-¹H COSY, HSQC and HMBC). Complete assignments of the NMR chemical shifts were obtained, providing a good reference for the further research of C₁₉-diterpenoid alkaloids.

The derivatives of esculetin contain hydroquinone groups that have various biological activities. In this study, the esculetin derivatives 2~14 were obtained by inducting the methoxy and hydroxyl groups into the 5, 6, 7 and 8 positions, and pheny group into the 4 position of esculetin (1), respectively. The structures of these derivatives were analyzed by the combined use of a number of nuclear magnetic resonance (NMR) spectroscopy techniques, including ¹H and ¹³C NMR, ¹H-¹³C HSQC and ¹H-¹³C HMBC. The ¹H and ¹³C NMR chemical shifts of the compounds were assigned. The effects of different substituents on the chemical shifts were discussed. The NMR shifts of esculetin derivatives were also calculated using the quantum chemical calculation method of gauge-invariant atomic orbitals (GIAO) and continuous set of gauge transformations (CSGT). And the calculated ¹H and ¹³C NMR chemical shifts were compared with their experimental values.

Azilsartan is a novel AT-1 angiotensin Ⅱ receptor blocker, which reduces blood pressure mildly without the side effect of cough. The drug is believed to have a large market potential. In this study, the drug was analyzed by ultraviolet spectroscopy (UV), infrared spectroscopy (IR), high resolution mass spectrometry (HRMS) and one-/two-dimensional magnetic resonance spectroscopy (i.e., ¹H NMR, ¹³C NMR, DEPT, ¹H-¹H COSY, HMQC and HMBC). The spectral data were carefully analyzed, interpreted and used to elucidate the structure of the compound.

With the continuous development of quantum chemical theories and advances in computer hardware and software, the methods for quantum chemical calculation of nuclear magnetic resonance parameters (qcc-NMR) are improved significantly in the past decade. With these methods, accurate calculated results can often be obtained at a relatively low cost. Furthermore, the methods for result analysis have been advanced from simple statistical parameters to more sophisticated procedures based on more complicated statistical methods or artificial neuron networks, etc. These advances make qcc-NMR a significant complement to traditional spectrometric methods, and more and more useful in natural product research. In this paper, the application of qcc-NMR in natural product research is reviewed. Representative researches featuring the use of qcc-NMR are highlighted.

Right ventricle (RV) segmentation is essential for assessing cardiac function in patients with pulmonary hypertension, tetralogy of Fallot, and so on. However, it remains difficult due to the complex structure of heart, thin myocardium and large variability of the RV, as well as the interferences from the fat nearby. Due to its high temporal and spatial resolution, cardiac cine magnetic resonance imaging is widely used for functional evaluation of the heart. This article reviews the commonly-used methods for RV segmentation from the cardiac cine magnetic resonance images. The traditional algorithms are described first, followed by the novel multi-atlas and deep learning methods. Lastly, the evaluation standards for RV segmentation are introduced. It is concluded that the deep learning-based segmentation methods may have the potential to become the method of choice in clinical settings due to their high efficiency and accuracy in the diagnosis and prognosis of the heart-related diseases.

Diffusion tensor imaging measures three-dimensional distribution of water molecule displacement in tissues, and has been widely used to study the structure of the brain. The technique has attracted wide research interests in recent years. Interpolation is often needed in the acquisition and reconstruction of diffusion tensor images to improve spatial resolution and/or facilitate visualization, especially when the images are used for white matter fiber tracking and registration in human brain. In this paper, the existing tensor interpolation methods are reviewed. The theory underlying the interpolation methods is described first. The technical challenges and limitations of the currently-used methods are then reviewed, followed by the introduction to the evaluation indices of the interpolation methods. The performance of typical interpolation methods is then compared with simulated data and real experimental data. The future direction of the development of tensor interpolation method is suggested.

With the shift toward the study of systems in operando and with increasing sensitivity, in operando nuclear magnetic resonance (NMR) is becoming more and more widely used in the field of polymer materials. In operando liquid state NMR provide mechanistic and kinetic information on polymerization reactions with the needless for stable labeling isotope, fast analysis, wide application range and maintaining intact samples. In addition, using the hyphenation of other characterization methods with in operando NMR spectroscopy is one of the most powerful methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures by designing a suitable probe. In operando NMR spectroscopy will remain an indispensable and versatility tool in macromolecular science for years to come.