South-north asymmetry of proton density distribution in the Martian magnetosheath

We perform a statistical analysis of data from the Mars Atmosphere and Volatile Evolution (MAVEN) project on the global distribution of protons in the Martian magnetosheath. Our results show that the proton number density distribution has a south-north asymmetry. This south-north asymmetry is most likely caused by the south-north asymmetric distributions of the crustal magnetic fields at Mars. The strong crustal magnetic fields push the inner boundary of magnetosheath to a higher altitude in the southern hemisphere. Due to the outward movement of the inner boundary of the magnetosheath, a compressed magnetosheath forms, causing subsequent increases in proton number density, thermal pressure, and total pressure. Eventually, a balance is reached between the increased total pressure inside the magnetosheath and the increased magnetic pressure inside the induced magnetosphere. Our statistical study suggests that the Martian crustal magnetic fields can strongly affect the proton number density distribution in the Martian magnetosheath.

Quantitative Evaluation of Fat Composition in Lumbar Vertebral Body and Paraspinal Muscle by Proton Density Fat Fraction with MRI

Purpose: Bone marrow and muscle adiposity have been considered to correlate with osteoporosis and Sarcopenia. Proton Density Fat Fraction (PDFF) can be measured by Magnetic Resonance Imaging (MRI). The purpose of the present study was to measure PDFF in the lumbar spine, paraspinal muscle and subcutaneous fat tissue. Methods: Participants were comprised of 30 patients (18 males, 12 females;age range, 14 - 87 years) who underwent MRI due to low back symptoms. PDFFs for the body of the fourth lumbar vertebra (L4), paraspinal muscle, and subcutaneous fat were measured. Results: PDFFs of the vertebral body and subcutaneous fat were significantly higher than that of paraspinal muscle (p < 0.001). PDFF was significantly higher for subcutaneous fat than for the vertebral body (p < 0.001). Although no significant differences in PDFF of the vertebral body, paraspinal muscle, and subcutaneous fat between females and males, PDFFs of the vertebral body and paraspinal muscle were significantly higher in older subjects (>63 years) than in younger subjects (Conclusions: PDFF of the vertebral body was significantly higher than that of paraspinal muscle. PDFFs of the vertebral body and paraspinal muscle were significantly lower in younger subjects than in older subjects.

Two-point Dixon and six-point Dixon magnetic resonance techniques in the detection,quantification and grading of hepatic steatosis

BACKGROUND Hepatic steatosis is a very common problem worldwide.AIM To assess the performance of two-and six-point Dixon magnetic resonance(MR)techniques in the detection,quantification and grading of hepatic steatosis.METHODS A single-center retrospective study was performed in 62 patients with suspected parenchymal liver disease.MR sequences included two-point Dixon,six-point Dixon,MR spectroscopy(MRS)and MR elastography.Fat fraction(FF)estimates on the Dixon techniques were compared to the MRS-proton density FF(PDFF).Statistical tests used included Pearson’s correlation and receiver operating characteristic.RESULTS FF estimates on the Dixon techniques showed excellent correlation(≥0.95)with MRS-PDFF,and excellent accuracy[area under the receiver operating characteristic(AUROC)≥0.95]in:(1)Detecting steatosis;and(2)Grading severe steatosis,(P<0.001).In iron overload,two-point Dixon was not evaluable due to confounding T2*effects.FF estimates on six-point Dixon vs MRS-PDFF showed a moderate correlation(0.82)in iron overload vs an excellent correlation(0.97)without iron overload,(P<0.03).The accuracy of six-point Dixon in grading mild steatosis improved(AUROC:0.59 to 0.99)when iron overload cases were excluded.The excellent correlation(>0.9)between the Dixon techniques vs MRSPDFF did not change in the presence of liver fibrosis(P<0.01).CONCLUSION Dixon techniques performed satisfactorily for the evaluation of hepatic steatosis but with exceptions.

Detection of hepatic and pancreatic fat infiltration in type II diabetes mellitus patients with IDEAL-Quant using 3.0T MR： comparison with single-voxel proton spectroscopy

Background Type II diabetes mellitus usually related to visceral and other organ （ectopic） fat. The purpose of this study was to detect hepatic and pancreatic fat infiltration in type II diabetes meUitus patients using 3.0T magnetic resonance （MR） and to compare the performance of iterative decomposition of water and fat with echo asymmetry and least-squares estimation （IDEAL-Quant） with single-voxel proton spectroscopy （HI-MRS）. Methods The study protocol was approved by our Institutional Review Board. Written informed consent was obtained from each subject in this study. We prospectively performed IDEAL-Quant and single-voxel proton spectroscopy with an echo time of 35 ms on 24 type II diabetes patients and 10 healthy volunteers. The hepatic proton density fat fraction （HPDFF） and pancreatic proton density fat fraction （PPDFF） were calculated, compared, and analyzed by t-tests and Spearman＇s correlation. Results The HPDFF and PPDFF measured with IDEAL-Quant were significantly different between the healthy volunteers and type II diabetes patients （th=9.377, P=0.000; tp=2.813, P=0.008）. The HPDFF and PPDFF measured with MRS were also significantly different between the healthy volunteers and type II diabetes patients （th=5.342, P=0.000; tp=2.63, P=0.013）. The HPDFF and PPDFF measured by the two methods were in good agreement （rh=0.854, P=-0.000; rp=0.774, P=0.000）. The HPDFF and PPDFF were not significantly correlated with each other （rMRs=0.203, p=0.248; rpDEAL_Quant=0.301, P=0.084）. The PPDFF measured with IDEAL-Quant was associated with body mass index （t=0.377, P=0.028）. Conclusion IDEAL-Quant is a nice method for hepatic and pancreatic fat detection, and it can be applied in clinical practice.

Structure of β-emitting nuclei ^(29)P

The extoic structure of 29P was investigated by measuring its magnetic moment in the ground state with β-NMR method. We got the experimental value of 1.2346 μN after diamagnetism correction. It is very close to the calculated value of 1.1009 μN computed with shell model. The shell model calculation also gave a proton density distribution of 29P with a long tail. The present results show that 2s1/2 proton in the 29P may lead to the proton-skin structure.

Optimization of magnetic resonance sequences in lymph node staging of nasopharyngeal carcinoma

Background Detection rate of retropharyngeal lymph node metastasis in patients with nasopharyngeal carcinoma （NPC） needs to be improved. The purpose of this study was to compare three magnetic resonance （MR） sequences for detecting lymph nodes in patients with NPC. Methods Between July 2007 and March 2008, MR staging of pre-treated tumor was conducted on 120 patients with pathologically confirmed NPC. The outcome of three different sequences for MR NPC staging were compared： coronal short T1 inversion recovery （STIR）, axial proton density fat-suppressed （PDWI fs）, and coronal contrast enhanced fast spin echo T1 weighted fat-suppressed （CE FSE TlWl fs）. Nodal classification method （1999） was applied to count the number of retropharyngeal and cervical lymph nodes discovered by each MR sequence. Paired t tests were used for statistical analysis. Results A total of 2575 lymph nodes were found using coronal STIR sequence; 1816 lymph nodes for coronal CE FSE TIWI fs sequence and 2638 lymph nodes for axial PDWl fs sequence. Significant differences existed in the number of lymph nodes detected by axial PDWI fs and coronal CE FSE T1WI fs sequence （paired t test, P 〈0.05）, with the former sequence getting higher numbers. Statistical differences also existed between coronal STIR and coronal CE FSE TlWl fs sequence （paired ttest, P 〈0.05）, with the former sequence getting higher numbers. No significant difference was found between coronal STIR sequence and axial PDWI fs sequence （paired ttest, P 〉0.05）. Conclusions For the detection of retropharyngeal and cervical lymph nodes, coronal STIR sequence and axial PDWI fs sequence have similar performance and both sequences showed better detection than CE FSE TIWI fs sequence. Furthermore, by combining coronal STIR sequence and axial PDWI fs sequence, we can improve the detection of lymph nodes in NPC N-staging before treatment, especially for lymph nodes located in the thoracic entrance.

Discrepancies between Nonalcoholic and Metabolic-associated Fatty Liver Disease by Multiple Steatosis Assessment

Background and Aims:The redefinition of metabolic-as-sociated fatty liver disease(MAFLD)from nonalcoholic fat-ty liver disease(NAFLD)has caused a revolution in clinical practice,and the characteristics of patients with steatosis but not MAFLD remain unclear.The aims were to compare the diagnosis rate of MAFLD in NAFLD using different steato-sis methods and explore the features of non-MAFLD-NAFLD and MAFLD-non-NAFLD.Methods:A cross-sectional study enrolling consecutive individuals was conducted at three medical centers in southern China from January 2015 to September 2020.Steatosis was evaluated by liver biopsy or magnetic resonance imaging-based proton density fat frac-tion(MRI-PDFF),ultrasound,controlled attenuation param-eter(CAP),and fatty liver index(FLI).Fibrosis was assessed by the NAFLD fibrosis score,transient elastography,or shear wave elastography.Results:The study enrolled 14,985 Chi-nese adults.The agreement of MAFLD and NAFLD diagnoses were 83%for FLI,95%for ultrasound,94%for both CAP and MRI-PDFF,and 95%for liver biopsy.The body mass index,blood pressure and lipid levels among non-MAFLD-NAFLD pa-tients were similar metabolic parameters(p>0.05 for all),but not the alanine aminotransferase and the proportion of pa-tients with insulin resistance,which were significantly higher in non-MAFLD-NAFLD with significant fibrosis.Conclusions:The new MAFLD definition ruled out 5-17%of NAFLD cases.NAFLD and MAFLD-NAFLD involved more severe metabolic abnormalities than MAFLD and MAFLD-non-NAFLD.Non-MAFLD-NAFLD patients with significant fibrosis had more se-vere liver injury and increased glycemic dysregulation within the normal range.Attention should be paid to its progression.

New scheme to trigger fusion in a compact magnetic fusion device by combining muon catalysis and alpha heating effects

The application of laser pulses with psec or shorter duration enables nonthermal efficient ultrahigh acceleration of plasma blocks with homogeneous high ion energies exceeding ion current densities of 10^(12) A cm^(-2). The effects of ultrahigh acceleration of plasma blocks with high energy proton beams are proposed for muon production in a compact magnetic fusion device. The proposed new scheme consists of an ignition fusion spark by muon catalyzed fusion(μCF) in a small mirror-like configuration where low temperature D–T plasma is trapped for a duration of 1 μs. This initial fusion spark produces sufficient alpha heating in order to initiate the fusion process in the main device. The use of a multi-fluid global particle and energy balance code allows us to follow the temporal evolution of the reaction rate of the fusion process in the device. Recent progress on the ICAN and IZEST projects for high efficient high power and high repetition rate laser systems allows development of the proposed device for clean energy production. With the proposed approaches,experiments on fusion nuclear reactions and μCF process can be performed in magnetized plasmas in existing kJ/PW laser facilities as the GEKKO-LFEX, the PETAL and the ORION or in the near future laser facilities as the ELI-NP Romanian pillar.