An Experimental Proton Magnetic Resonance Spectroscopy Analysis on Early Stage of Acute Focal Cerebral Ischemia

U sing different m odels of focal cerebral ischemia,the temporal and spatial rules of m etabolism and energy changes in the post- ischem ia brain tissue were measured by proton m agnet- ic resonance spectroscopy(1 HMRS) to provide valuable inform ation for judging the prognosis of a- cute focal cerebral ischemia and carrying out effective therapy.Nine healthy Sprague- Dawly rats (both sexes) were randomly divided into two groups:The rats in the group A(n=4 ) were occlud- ed with self- thrombus for1h;The rats in the group B(n=5 ) were occluded with thread- em boli for1h.The 1 H MRS at30 ,4 0 ,5 0 ,6 0 min respectively was examined and the m etabolic changes of NAA,Cho and L ac in the regions of interest were sem iquantitatively analyzed. The spectrum intregral calculus area ratio of NAA,Cho,L ac to Pcr+Cr was setas the criterion.The values of NAA· Cho in the regions of interest were declined gradually within 1h after ischem ia, especially,the ratio of Cho/ (Pcr+Cr) ,NAA/ (Pcr+Cr) at6 0 m in had significant difference with that at5 0 min(P<0 .0 5 ) .The ratio of L ac/ (Pcr+Cr) began to decrease at4 0 min from initial in- crease of L ac in both A and B groups.MR proton spectrum analysis was a non- invasive,directand com prehensive tool for the study of cellular metabolism and the status of the biochemical energy in acute ischem ia stroke.

Non-linear spectral splitting of Rydberg sodium in external fields

We have studied highly excited sodium in various electric fields, parallel electric and magnetic fields, with one σ andπ photon irradiation, and even in a magnetic field with a complex laser polarization configuration. The σ spectra shows a simple linear Stark effect with the applied electric field, while the π spectra exhibits a strong non-linear dependence on the electric field. The π transitions in parallel fields show a similar behavior to that in a pure electric field but the spectra get more smooth due to the magnetic field. The diamagnetic spectrum with laser polarization angles between 0 and π /2 proves that it can be reproduced by simple linear combination of π and σ components, indicating there is no interference between the π and σ channels. A full quantum calculation considering the quantum defects accounts for all the observations. The quantum defects, especially for the channel np, play an important role in the spectral profile.

Time-resolved energy spectrum measurement of a linear induction accelerator with the magnetic analyzer

We recently set up a time-resolved optical beam diagnostic system. Using this system, we measured the high current electron beam energy in the accelerator under construction. This paper introduces the principle of the diagnostic system, describes the setup, and shows the results. A bending beam line was designed using an existing magnetic analyzer with a 300 mm-bending radius and a 60° bending angle at hard-edge approximation. Calculations show that the magnitude of the beam energy is about 18 MeV, and the energy spread is within 2%. Our results agree well with the initial estimates deduced from the diode voltage approach.

Magnetic resonance spectroscopy in the diagnosis of cognitive impairment in AIDS patients

Background The pathological abnormalities of the AIDS patients lie in the subcortical regions of the brain, specifically the deep white matter and basal ganglia, while the extent of pathology generally correlates with the severity of cognitive impairments in the white matter and basal ganglia. Brain metabolite changes of these lesions can reflect the pathological abnormalities. The purpose of this study was to assess the value of magnetic resonance spectroscopy （MRS） in the diagnosis of cognitive impairment in AIDS patients.Methods 3.0T MR was used to measure N-acetyl aspartate （NAA）, choline （Cho）, myo-inositol （MI） and creatinine （Cr）in the frontal white matter, basal ganglia and parietal cortex of 21 AIDS patients with dementia complex （ADC）, 19 AIDS patients with neuroasymptomatic （NAS） and 20 seronegative （SN） controls. Then we compared the difference of metabolic rate between AIDS patients and SN groups.Results NAA/Cr （mean=1.2502, SD=0.1600） was significantly decreased and Cho/Cr （mean=1.2028, SD=1.1655） was increased in the frontal white matter in ADC group, while NAA/Cr （mean=1.5334, SD=0.0513） was reduced in NAS group when compared with SN group. NANCr in the basal ganglia was decreased in both ADC and NAS groups （mean=1.2625,SD=0.1615 and mean=1.5278, SD=0.0380, respectively）. Cho/Cr （mean=1. 1631, SD=0.0981） was markedly increased in ADC group. Although NAA/Cr, Cho/Cr and MI/Cr in the parietal cortex had a certain change in both ADC and NAS groups compared with SN group, the differences were not statistically significant.Conclusions The brain metabolite changes of AIDS patients are correlated with cognitive impairments. MRS can be used as a valuable inspection method to assess cognitive impairments in AIDS patients.