After the production of the gradient coil of the magnetic resonance imaging system, electromagnetic field testing is required to verify whether the assembly accuracy meets the electromagnetic field requirements. Since the passive magnetic field B _z satisfies the Laplace ^,s equation and is a harmonic function, and according to the extreme value principle of harmonic function, the maximum or minimum values of B _z can only appear on the boundaries, so the observation points of the magnetic field are generally selected on the surface of the spherical imaging area. For superconducting magnets used for human body magnetic resonance imaging, a spherical area with a center diameter of 40~50 cm is generally selected as the shimming target area. Only the field value of the target area needs to be measured, and the spherical harmonic coefficients obtained after data processing are used to determine the magnetic field performance of the gradient coil. There are many testing principles and methods for electromagnetic fields, so there is no unified way and method in the field of commercial applications. This article is based on the Gauss-Legendre numerical integration, measures and analyzes the magnetic field performance of gradient coils by building a data acquisition system, and this article applies numerical analysis methods to calculate the spherical harmonic coefficients of the magnetic field using discrete test data, providing a feasible method for the production and testing of gradient coils.
Magnetic Resonance Imaging/methods* ; Magnetic Fields ; Electromagnetic Fields ; Equipment Design

Objective:To study the clinical characteristics and compliance of early-onset gout patients by case-control analysis.Methods:A total of 111 early-onset patients (onset age ≤35 years old) were included as Group A, and 111 non-early-onset patients (onset age >35 years old) with matched disease durationwere included as Group B. The differences ofclinical characteristics, causes of acute gout attack, dairy diet habits, compliance, and misunderstanding of the disease were compared.Results:Compared with the non-early-onsetgoutpatients, the early-onset patients had a higher proportion of obesity (63 cases vs 28 cases), family history (36 cases vs 20 cases) and tophus (39 cases vs 23 cases) and higher level of VAS scores (8.5±1.3 vs 7.6±1.7; χ2=22.988, P<0.01; χ2=5.749, P=0.016; χ2=5.729, P=0.017; t=4.639, P<0.01), lowerproportionof the first metatarsophalangeal joint involvement as the initial joint involvement (45.9%, 51 cases vs 59.4%, 66 cases; χ2=4.066, P=0.044), higher proportion of the ankle involvement as the initial joint involvement (34.2%, 38 cases vs 21.6%, 24 cases; χ2=4.386, P=0.036), higher proportion of alcohol drinkers and high fructose drinkers, which was more likely to relate to alcohol intake, strenuous exercise and high fructose intakeas trigger of the flare ( χ2=6.513, P=0.011; χ2=7.126, P=0.008; χ2=1.978, P=0.160), while the proportion of regular exercisers and on diet in the family was lower ( χ2=22.887, P<0.01; t=-4.917, P<0.01). The proportion of poor diet and medication compliance in Group A was higher than that in Group B(57.7%, 64 cases vs 38.7%, 43 cases; χ2=5.207, P=0.022; χ2=5.867, P=0.015). As for the reason for poor treatment compliance, early-onset gout patients were more worry about the side-effects of drugs than non-early onset patients ( χ2=4.190, P=0.041). There was no significant difference between the two groups in the main misunderstanding of gout. Conclusion:Although early onset gout patients are young, their condition is more serious, and compliance is poorer, this group of patients should be highly valued in clinical diagnosis and treatment.

Objective To investigate the inhibitory effect of methylprednisolone (MP) on the development of coronary arteritis in a murine model of Kawasaki disease (KD) induced with a candida albicaus watersoluble fraction (CAWS).Methods Forty-five C57BIL/6mice were evenly divided into three groups (the control group,the CAWS group and the MP group).Mice in the CAWS group were intraperitoneally injected phosphate buffer saline (PBS) for 5 days.MP or PBS was administered to the different group.The animals were sacrificed at day 3,day 10 and day 28,and the status of vasculitis in the coronary arteries and the aortic root was investigated histologically.One-way analysis of variance (ANOVA) was used to compare the differences among three groups,and t-test for two independent groups.Results The mice in CAWS group and MP group,which induced by CAWS,showed that the body weight and heart weight decreased significantly,and the spleen weight was increased at day 10 and day 28 (P＜0.05).Vasculitis was induced in the mice of those two groups,and the severity score was the highest at day 10 (12.7±0.5).In addition,the severity of the inflammation of the aortic root and the coronary arteries were reduced in MP group (t=6.35,5.55,2.8,P＜0.05).Elastic fiber staining showed that the layers of vascular walls were in disorder and elastic fibers were broken in the CAWS group.However,there was no disruption or breakage in the MP group.Conclusion MP can suppress the progression of coronary arteritis in this CAWS-induced murine vasculitis model,which indicates the efficacy of MP in KD patients with coronary artery lesions.

In the pathophysiology experiment teaching,by combining the teaching of prob-lem-based learning with local area network(LAN) teaching,students first carry out a simple ex-periment to ask a question on the observed phenomenon,and then put forward a hypothesis,de-sign experiments to answer questions,and implement the experiment,and finally present experi-mental results.Such experimental design teaching is not only a great way to mobilize the stu-dents’interest in scientific research and learning initiative,but also greatly enhances the effi-ciency of the experiment.Students preliminarily master the basic scientific research program and methods.

Objective To compare the cytokine expression profile of 3 CD8+, 3 CD4+ and 3 gamma delta-positive T cell clones derived from the synovial fluids of reactive arthritis (ReA) patients and to explore the immunological pathogenesis of ReA. Methods Complementary DNA-based microarrays containing genes for 56 cytokines were used for screening the expression profile of 3 CD8+, 3 CD4+ and 3 gamma delta-positive T cell clones derived from the synovial fluids of 3 reactive arthritis (ReA) patients. Results Transcripts encoding for interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were expressed among all CD8+ and CD4+ T cell clones by microarray. Expression of these cytokines could be verified by RT-PCR in 14 out of 15 microarray experiments. Lymphotoxin (LT)-alpha and granulocyte macrophage colony-stimulating factor (GM-CSF) were also consistently expressed among CD4+ cells. However, ??+T cells revealed a different cytokine pattern, mainly expressing transforming growth factor (TGF)-beta 2 and GM-CSF. Conclusion CD8+ and CD4+ T cells mainly reveale a Th1-mediated profile, whereas ??+T cells expresse less pro-inflammatory cytokines resembling a Th3-driven pattern. T lymphocyte clones from the joint of ReA patients exhibit different cytokine expression profiles refelecting their different roles in pathogenesis.