| AIMS: There were three aims in this study: Firstly, a reliable method to detect GABA in vivo steadily was explored by the simulation experiment and clinical phantom in this study. Secondly, a quantification technique based on QUEST was discussed for detecting GABA in vivo. And thirdly, 2D J-resolved MRS was used to measure absolute concentration of brain metabolites.MATERIALS AND METHODS:We utilized DQF technology in the design and optimization of pulse sequence for measurement of GABA. We adopted product operator and coherence selection theories to discuss the pulse sequence design process and how does the sequence pulse work effectively, and described its mathematical formula.This paper studied quantification method of metabolite based on the prior knowledge of brain metabolites. The separate and quantify of all kinds of 1H MRS metabolites combining with QUEST were obtained. The method of quantitative detection the concentration of in vivo brain metabolite was advanced. Eleven kinds of spectroscope prior knowledge on main metabolite by combining MRUI(Magnetic Resonance User Interface)with SCOPE simulation.The concentration of NAA, Cr and GABA in mice's brain were detected by 2D J-Resolved MRS.RESULTS:In the simulation experiment using NMR-SCOPE, it was obvious that the Cr signal at 3.0 ppm was suppressed and the very low GABA signal was enhanced clearly with the optimized DQF-PRESS pulse sequence.Fitting spectral was processing in jMRUI software package. The quantification results showed that the concentration of Asp was 2.59±0.83(mmol/kg), Cho was 2.32±0.25(mmol/kg), GABA was 3.54±0.57 (mmol/kg), Glu was 6.97±0.83 (mmol/kg), Glc was 0.19±0.46(mmol/kg) and Gln was 0.60±0.16(mmol/kg). Cr+PCr, which concentration was 7.5 mmol/kg, were used as internal reference. Compared with related reference article, the CRBs range of ten metabolites was from 1% to 10%. Therefore, the results were reliable. The result for 1D MRS detection of brain GABA concentration was 0.37±0.01μmol/g, and that for 2D J-resloved spectroscopy atδ1.92 peak, GABA was 0.30±0.13μmol /g. It was noteced that the results for 1D and 2D are basically the same. The rat cerebellum GABA by 1D MRS gave the average concentration of 0.19±0.01μmol/g, and 2D MRS measured concentration was 0.30±0.05μmol/g. The error for the two methods was acceeptable. The cerebral and cerebellar concentration of Cr was 0.14±0.05μmol/g for 1D MRS, and it was 0.17±0.06μmol/g for 2D MRS,. The difference for the two methods was also very small .The results of NAA concentration measured with 1D MRS and 2D MRS were basically the same.CONCLUSION:A useful method is provided for detecting GABA in vivo in this study. Also, the mathematical formula of pulse sequence and theory of pulse design will help the others to under pulse sequence and design pulse sequence. Meanwhile, we have phantom experiment by clinic PRESS sequence to prove the feasibility of detect GABA using LCModel. The results prove that LCModel is an effective post-processing way to separate GABA form the background of Cr.The quantification method of metabolite based on the prior knowledge of brain metabolites can detect weak signal coved by noise. This method offered new path for detect brain metabolites such as GABA in vivo and achieve good results.The two-dimensional J-resolved technology can detect several metabolite concentrations. This result is well satisfied with clinical requirements. Compared with other methods, the two-dimensional J-resolved technology is more accurate and reliable.Three kinds of method for detecting GABA in brain by magnetic resonance spectroscopy were established in this study. These methods offered new paths for understanding the mechanism of neural regression disease, forecasting and diagnosing of this kind of disease and the assessment of treatment effect. Meanwhile, there is a higher value.
|
PDF Full Text Request