Local cerebral metabolic rate of glucose(LCMRGlc) is an important index for the description of neural function.Dynamic 18 F-fluoro-2-deoxy-D-glucose(FDG) positron emission tomography(PET) has been used for quantitative imaging of LCMRGlc in humans,but is seldom used routinely because of the difficulty in obtaining the input function noninvasively.A reference tissue-based Patlak plot model(rPatlak) was proposed to generate parametric images of LCMRGlc in a quantitative dynamic FDG-PET study without requiring blood sampling.Dynamic emission scans(4×0.5,4×2 and 10×5 min) were acquired simultaneously with an IV bolus injection of 155 MBq of FDG.Arterial blood samples were collected during the scans via a catheter placed in the radial artery.Simulation data were also generated using the same scan sequence.The last ten scan data sets were used in a graphical analysis using the Patlak plot.The ratio of LCMRGlc estimated from the original Patlak(oPatlak,using plasma input) was used as the gold standard,and the standardized uptake value ratio(SUVR) was also calculated for comparison.Eight different tissues including white matter,gray matter,and whole brain were chosen as reference tissues for evaluation.Regardless of the reference region used,the slopes in the linear regression between oPatlak and rPatlak were closer to unity than the regression slopes between oPatlak and SUVR.The intercepts for the former were also closer to 0 than those for the latter case.The squared correlation coefficients were close to 1.0 for both cases.This showed that the results of rPatlak were in good agreement with those of oPatlak,however,SUVR exhibited more deviation.The simulation study also showed that the relative variance and bias for rPatlak were less than those for SUVR.The images obtained with rPatlak were very similar to those obtained with oPatlak,while there were differences in the relative spatial distribution between the images of SUVR and oPatlak.This study validates that the rPatlak method is better than the SUVR method and
WU YiGenZHOU YunBAO ShangLianHUANG SungChengZHAO XiaoHuLI Jun
目的探讨耳鸣的相关脑区及中枢机制。方法应用功能性磁共振成像(functional magnetic resonance imaging,fMRI)技术,研究20例耳鸣患者的静息状态下fMRI特征,并以20例无耳鸣的正常人静息态作对照。用专门的统计分析软件(SPM2软件及北京师范大学的局部一致性分析软件)进行数据分析。结果①耳鸣组强于对照组的活动脑区为:双侧颞上回后部(BA42)、扣带回后部(BA31)、额中回感觉运动区(BA6)、双侧顶下小叶(BA40)及脑干;②耳鸣组低于对照组的活动脑区包括双侧颞叶中区(BA37)、楔前叶(BA7)、左侧额中回(BA8)、右侧额下回(BA10)。结论与对照组比较,耳鸣组静息状态下fMRI显示部分相关脑区活动增高,部分相关脑区活动减低。提示大脑皮层参与耳鸣过程,为耳鸣的中枢皮层重塑机制假说提供基础资料,也为今后耳鸣的客观诊断的研究提供又一新线索。
