A new multifunction X-band electron paramagnetic resonance (EPR) spectrometer is designed and produced, which is equipped with a new operation system based on the EPR control and readout system (CRS). The new continuous-wave (cw) dual-mode resonator and the dielectric resonators for respectively the pulsed EPR and transient EPR (trEPR) are designed purposely. The adoption of CRS system improves significantly the integration and expandability. The spectrometer is equipped with cryogen-free EPR variable temperature system with a range of 6~300 K. Thereafter, three typical samples are used to demonstrate the elegant design of the spectrometer by the cw dual-mode EPR, pulsed EPR and trEPR experiments. Perspectively, this design herein will be a criterion or option of the new generation of EPR spectrometer.

In this work, a new magnetic resonance imaging (MRI) contrast agent based on organic gadolinium (Gd) nanoparticles was designed, synthesized and tested. Based on a biocompatible condensation reaction between 1, 2-aminothiol and cyano group, organic Gd nanoparticles with well-controlled diameter in the range of 8~23 nm were successfully synthesized. When used as the MRI contrast agent, the organic Gd-nanoparticles exhibited slowly weakened longitudinal relaxivity with time. Meanwhile, its transverse relaxivity was observed to be enhanced firstly and then gradually weakened, which could be attributed to the diameter increase of the Gd-nanoparticles. The simultaneous existence of time-dependent longitudinal and transverse relaxivities of the organic Gd-nanoparticles suggests their potential to be advanced T₁-T₂ dual-modal contrast agent for MRI.

Recovering dynamic magnetic resonance imaging (MRI) from highly undersampled raw data is of great significance, and is an important approach for achieving both high temporal and spatial resolution in dynamic contrast enhanced imaging. In this study, a method for 3D dynamic MRI with high spatiotemporal resolution and motion insensitivity was developed, which combines golden angle variable density spiral trajectory, parallel imaging and homotopic l₀ minimization-based compressed sensing. Golden angle variable density spiral trajectory, which has the advantages of high data acquisition efficiency and motion insensitivity, was used to acquire k-space data. In the reconstruction algorithm, multicoil sparsity constrain was applied in the temporal total variation domain and l₀ minimization, instead of traditional l₁ minimization, was adopted, which could further increase the undersampling rate. Simulations and in vivo experiments demonstrated that high spatial resolution and temporal resolution can be achieved by the proposed method while maintaining the image quality. This study also suggested the advantages of homotopic l₀ norm-based 3D dynamic MRI reconstruction and its clinical potential.

Chemical exchange saturation transfer (CEST) imaging shows great potential in clinical applications. However, CEST imaging is challenging in abdomen due to the large B₀ shift. Meanwhile, the nuclear Overhauser enhancement (NOE) effect contaminates amide proton transfer (APT) image when using the conventional asymmetry analysis. In this paper, a CEST post-processing approach based on neural network fitting was proposed. Through recognizing the characteristics of acquired Z-spectrum, the background reference Z-spectrum and the B₀offset were obtained and used to correct the acquired Z-spectrum. The APT effect and NOE effect could be calculated by subtracting the background reference Z-spectrum from the acquired Z-spectrum. The proposed CEST post-processing approach was validated by the egg white imaging and the abdomen imaging on four healthy volunteers.

T staging plays an important role in the preoperative evaluation of rectal cancer. However, the traditional stage judging method directly based on the patients' MRI images is not effective. In this paper, we proposed to predict the T-stage of rectal cancer by using radiomics. First, the imaging data of 105 patients with rectal cancer were obtained, the patients in T1 and T2 stages were classified as non-breakthrough muscular layer group (31 cases), and the patients in T3 and T4 stages were classified as breakthrough muscular layer group (74 cases). In the axial T2WI image of patients, the region of interest (ROI) was segmented, and the radiomics features were extracted using the pyradiomics toolkit. The high-dimensional features were selected using least absolute shrinkage and selection operator (LASSO), and the feature data highly related to T stage were obtained. Four machine learning methods including logistic regression, support vector machine (SVM), gradient boosting decision tree (GBDT) and random forest were used in modeling respectively. Cross validation was performed to evaluate the performance of each model. 100 dimensional features were extracted from each image layer, and 7 features highly related to T stage were obtained after lasso feature selection. Among the four machine learning methods, SVM performed best. The average area under curve (AUC), accuracy, sensitivity and specificity of SVM method were 0.968 5, 0.886 4, 0.962 5 and 0.899 2 respectively, and the accuracy of verification set reached about 0.904 7. The result proved that radiomics can greatly improve the accuracy of T-stage prediction of rectal cancer.

This paper performed a retrospective analysis of 19 patients diagnosed with pathologically-verified WHO Ⅱ-Ⅲ grade glioma with T₂/FLAIR mismatch sign. We extracted the overall characteristics of the tumor area and the image parameters of the mismatch regions from the patients' imaging data for quantitative analysis. Afterward, we investigated how T₂/FLAIR mismatch sign affected the diagnostic efficacy for isocitrate dehydrogenase (IDH)-mutant and 1p/19q non-codeleted (IDH^MUT/1p/19q⁺) lower-grade gliomas (LGG). This study showed that the overall and partial T₂/FLAIR mismatch sign can be used as an imaging marker to predict IDH^MUT/1p/19q⁺ LGG. The overall imaging characteristics of the tumor area combined with the quantitative parameters of the mismatch regions can improve the diagnostic efficacy for IDH^MUT/1p/19q⁺ LGG.

Somatic symptom disorder (SSD) is a common medical disorder characterized by various biological, psychological, and social pathogenic factors. At present, little is known about the neural mechanism of SSD. This study evaluated the dysfunction in 45 patients with SSD and 43 controls by combining the amplitudes of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) methods with resting-state functional magnetic resonance imaging (fMRI). The patients with SSD exhibited significantly greater ReHo values in the right middle cingulate gyrus, and smaller ReHo values in the right precuneus, the left inferior temporal gyrus extending to the left middle temporal gyrus and the left parahippocampal gyrus, and the right pons compared with the controls. The SSD patients showed higher ALFF values in the middle cingulate gyrus extending to the left middle frontal gyrus, the right insula extending to the right inferior frontal gyrus, and left middle frontal gyrus extending to the left anterior cingulate cortex. These dysfunction areas are involved in self-relevant processes, emotional processing, and body perception, which are closely related to the pathogenesis of SSD.

The left myocardium is the strongest cardiac muscle, representing the ability of heart to pump arterial blood throughout the body. Quantitative analysis of the contractive motion of left ventricle (LV) stands an important approach to diagnose cardiovascular diseases such as myocardial infarction. This paper utilized a biomechanical model describing the material of left myocardium to reconstruct the displacement field of LV. The mechanical model was used as an interpolation term, which was incorporated into the Bayesian estimation framework with the displacement field observed by cardiac cine magnetic resonance (CCMR) image, and the equation of displacement field was solved by finite element method. Functional parameters of LV were compared between the weak (46 cases) and normal (55 cases) ejection fraction groups of LV in the experiment. Significant differences in radial and circumferential displacement and velocity, strain and strain rate were observed between the two groups (p < 0.001), which proved that the method could effectively distinguish whether the motion of LV is normal or not. The experimental results are also highly correlated with the functional parameters of LV measured by CVI software, indicating that the method will facilitate the diagnosis of cardiovascular diseases.

Bcl-2 mainly executes anti-apoptotic function in the Bcl-2 family. Nuclear orphan receptor Nur77 can be translocated from nucleus to mitochondria, then interact with Bcl-2 to reverse the function of Bcl-2 from a cell protector to a cell killer, thereby inducing cell apoptosis. The function of Bcl-2 is regulated by post-translational modification, such as the phosphorylation of T69 in the intrinsically disordered loop between BH3 and BH4 motifs. However, due to the lack of structural information of the full-length protein, the effect of phosphorylation modification of T69 in the loop region on the interaction of the two proteins is still unclear, and there is a lack of related research at the atomic level. Therefore, we constructed a full-length intracellular Bcl-2 containing loop region and T69E mutant to mimic stable phosphorylation modification, and investigated the interactions by combining circular dichroism (CD), Western blot and nuclear magnetic resonance (NMR) methods. It was observed that the full-length Bcl-2 had a stronger interaction with Nur77 compared to the Bcl-2/xl chimera, and the phosphorylation modification mimicked by T69E weakened the interaction between Bcl-2 and Nur77. The results will promote future research based on Bcl-2 and Nur77 signal transduction pathways and the apoptosis targeting cancer cells.

Nuclear spin singlet state is a special spin state, whose main characteristic is that its lift-time can be much longer than the corresponding longitudinal/transverse relaxation time. It can be used to study molecular slow diffusion, slow motion, special signal selection or other molecular motion. In the literature, singlet states are mainly studied in an isolated two-spin system. Here we discuss the nuclear spin singlet state preparation in a three-spin system. The system consisting of three protons in the molecule N-acetyl aspartic acid (NAA) was used as an example. Specifically, we used optimal control theory and numerical calculation method to design the pulse sequence and to transfer the two spins in methylene group into singlet state. The shaped pulses including and not including the proton in the methyne group were designed respectively. Our simulation results indicate that to ensure a high efficiency for the singlet state preparation, the coupling of the proton in the methyne group should be included in the pulse calculation. Furthermore, the singlet state can be combined with two-dimensional pulse sequences such as COSY and NOESY. The experimental results show that some correlation peaks could be selectively observed in the two-dimensional spectrum based on singlet state. It will be useful for the spectral peak assignment especially in the case of serious spectral overlap.

The performance of the rubidium (Rb) atomic frequency standard has achieved significant improvement in recent years. Its frequency stability has already reached the order of 10^-13τ^-1/2. To further improve Rb frequency standard's stability performance, we developed a high signal-to-noise ratio (SNR) physics package whose cavity-cell assembly consists of a slotted-tube microwave cavity, separated filter and absorption cells. The microwave cavity has a homogenous field distribution along the quantization axis, and the filter and absorption cells are temperature-controlled independently. We also used an optical and isotopic filtering scheme to suppress shot noise from the pumping light. The physics package's final background photocurrent I₀ and the frequency discrimination slope K_dwere measured to be 95 μA and 7.7 nA/Hz, respectively, and the calculated limit stability of the shot noise of the physical package was 7.5×10^-14τ^-1/2. The result shows that Rb frequency standard can reach an unprecedented stability level below 1×10^-13τ^-1/2 as long as the electronic system's noise could be well controlled.

Transmit/receive (T/R) switch is used to switch the transmission and reception channels in nuclear magnetic resonance (NMR) spectrometer, which is required high isolation of high-power signals and low insertion loss of NMR signals. In addition, the general narrowband T/R switch is no longer applicable in broadband magnetic resonance spectrometer. This paper presents a positive-intrinsic-negative (PIN) diode-based T/R switch design with low insertion loss (less than 1 dB), high isolation of high-power signals (more than 75 dB) and short switching time (1 μs) in broadband (10~100 MHz). Substituting the broadband T/R switch for the narrowband T/R switch of the general probe, the NMR signals of hydrogen and fluorine nuclei at two different frequencies were measured on a 0.5 T NMR spectrometer, which verified the broadband performance of the T/R switch.