| The Effects of Sequence and Coil to the Test-Retest Reliability of Brain Morphometry AnalysisPurpose The aim of this study was to analyze and compare the reliability of scanning and segmentation of brain structures amongst three 3D T1 weighted sequences,Magnetization-Prepared Rapid Acquisition Gradient Echo(MPRAGE),Multiecho MPRAGE(MEMPRAGE)sequence and Magnetization-Prepared 2 Rapid Acquisition Gradient Echo(MP2RAGE)sequence.At the same time,to verify that if the results of the comparison were consistent in the total brain structure,total cortical structure,total subcortical structure and every brain structure.Also to explore whether the RF coil had an impact on image scanning and segmentation stability.In previous studies,the comparison of the scanning and segmentation reliability of these three sequences has not been able to draw an unified conclusion.Meanwhile,this experiment is also the first research which compared the three sequences at the same time in one experiment.Also the results of this study can provide a guide selection of the sequence and coil selection in our future studies of the scanning and analysis with the intracranial atherosclerosis patients.Materials and Methods Total of 24 healthy volunteers were prospectively recruited for brain structure image scanning.The sequences used for the scan were:MPRAGE,MEMPRAGE and MP2RAGE sequences and two coils:20-channel head and neck coil and 32-channel head coil.Repeated scanning is performed immediately after scanning with each sequence under each coil condition,and the image obtained by the two scans is analyzed to evaluate and calculate the repeatability of the scan.The following six scan conditions were obtained:MPRAGE sequence-20 channel coil combination,MPRAGE sequence-32 channel coil combination,MEMPRAGE sequence-20 channel coil combination,MEMPRAGE sequence-32 channel coil combination,MP2RAGE sequence-20 channel coil combination and MP2RAGE sequence-32 channel coil combination.Six different combinations were scanned in different orders,and 24 patients were randomly assigned to undergo different scan orders.MorphoBox and FreeSurfer software were used to segment the brain regions and obtain the volume of different brain regions.The test-retest variability(TRV)value was calculated using the segmentation results of two times,and the high TRV value meant low reliability.The reliability of six different scanning conditions was compared based on every different brain regions and statistical differences were calculated.At the same time,the TRV values of all the brain regions,all the cortical regions and all the subcortical regions brain region were put together and the reliability of the six different scan combination in them were also been compared.Results No matter which of the two software was used,the TRV values of all brain regions under all combinations were no more than 16.46%.The MorphoBox segmentation algorithm showed that for the whole brain structure,the MEMPRAGE sequence-32 channel coil combination had numerically lowest TRV value than all the other combinations.And whether with 20-channel coil or 32-channel coil,the TRV values of MEMPRAGE sequence were lower than the MPRAGE and MP2RAGE sequences.For total subcortical structure,the TRV values of the MP2RAGE sequence-32 channel coil combination was the smallest in numerical.And the TRV value of the MP2RAGE sequence was lower than the other two sequences whether with 20-channel coil or 32-channel coil.At the same time,the TRV value of the 32-channel coil was lower than the TRV value of the 20-channel coil whether combined with any of the three sequences,regardless of the total brain structure or the total subcortical structure.The results of analysis by FreeSurfer software are similar to those of MorphoBox,and the differences of TRV values under each scanning condition was more significant.In addition,according to the results of segmentation whether for volume or thickness measurement with FreeSurfer for cortical structures,the TRV of the MEMPRAGE-32 channel,MPRAGE-32 channel,and MEMPRAGE-20 channel were lower than that of the MP2RAGE-32 channel,MPRAGE-20 channel and MP2RAGE-20-channel,and the differences among different combinations were significant.Meanwhile,as for the results of every single brain region segmented by the two analysis methods,it were also consistent with the rules that for the cortical brain region,the most stable sequence was MEMPRAGE and for the subcortical brain region,the most stable sequence was MP2RAGE.While comparison of the 32-channel coil and the 20-channel coil,there was not any specific rule were found for single structure.Conclusion The scanning reliability of all sequence and coil combinations were good.For the total brain structure and total cortical brain structure,the scanning and segmentation reliability of the MEMPRAGE sequence was superior to the MPRAGE and MP2RAGE sequences.However,for the subcortical region,the scanning and segmentation reliability of the MP2RAGE sequence was slightly stronger than the other two sequences.Compared the reliability of 32-channel coil with 20-channel coil,the rule was not very obvious,while in general,the reliability of 32-channel coil was better than that of the 20-channel coil.Brain Perfusion and Structure Variation of Patients with Unilateral Middle Cerebral Artery evere Stenosis or OcclusionPurpose The aim of this study was to investigate the changes of brain volume in patients with unilateral middle cerebral artery atherosclerotic severe stenosis or occlusion,and to measure the cerebral perfusion level of this type of patients by multi-echo time ASL(mTI-ASL)technique.And to explore whether there was a correlation between variation of brain volume and variation of cerebral blood perfusion,to verify whether cerebral perfusion level may be an influencing factor of changes in brain volume of patients.The innovations of this experiment are mainly as follows.In the previous study,there were many studies about brain volume changes in patients with extracranial stenosis,but few studies focused on brain volume changes in patients with intracranial atherosclerotic stenosis.In addition,although there have been studies on cerebral perfusion changes in patients with intracranial stenosis,this study used a different mTI-ASL magnetic resonance technique different from previous studies,which can provide not only cerebral blood flow data but also blood arrival time values.Help us to better understand the patient’s brain perfusion status.Materials and Methods This research prospectively included patients with unilateral middle cerebral artery(MCA)atherosclerotic severe stenosis(>70%)or occlusion and healthy volunteers matched for age and years of education with the patients.The patients were divided into two groups based on the medical history and imaging information:the asymptomatic group and the TIA symptom group.Brain structure imaging was performed using 3D T1-weighted multi-echo magnetization preparatory fast gradient echo sequence(MEMPRAGE),and brain segmentation and volume assessment were performed on the subject using the MorphoBox algorithm,which is a volume-based analysis method.At the same time,the subjects were scanned with multi-inversion time ASL sequence(mTI-ASL),and the CBF values BAT values in the bilateral middle hemisphere through all subjects were obtained by ROI delineation of middle cerebral artery territory.In patients,the absolute volume of the brain region on the stenosis side was divided by the absolute volume of the non-stenosis lateral brain region to obtain a bilateral ratio(Rvolume)(in the healthy control group,left side was divided by right side).Similarly,the CBF value on the lesion side was divided by the CBF value on the non-lesion side to obtain the ratio(RCBF)(in the healthy control group,left side was divided by right side)and the lesion side BAT value was subtracted by the non-lesion side to calculates the BAT difference(DBAT)(in the healthy control group,left side was subtracted by right side).Furthermore,the Rvolume,RCBF,and DBAT values of the two groups of patients and the control group were compared by one-way ANOVA test to compare the differences between the three groups.At the same time,the relationships between Rvolume and RCBF and DBAT values in each brain region of the subjects were analyzed by Pearson correlation.Results The study included 38 patients with unilateral middle cerebral artery atherosclerosis or occlusion who met the inclusion criteria for analysis.There were 15 patients in the asymptomatic group and 23 patients in the TIA symptom group.At the same time,30 healthy volunteers were enrolled.There were no significant differences in basic population and medical history between the three groups(such as age,gender,and hypertension).At the same time,no statistical difference was found in white matter high signal scores and grades among the three groups.There was no significant difference in Rvolume between the asymptomatic group and the healthy controls.While the TIA symptom group compared with the other two groups,in the frontal lobe,the gray matter of the temporal lobe,the white matter of the parietal lobe,the white matter of the temporal lobe,the thalamus,the putamen,the deep white matter,the Rvolume values of patients were significantly reduced.In the asymptomatic group,RCBF was lower and DBAT was higher than the healthy control group.While in the TIA symptom group,the RCBF was lower and the DBAT was larger than the asymptomatic group.The differences were statistically significant.In addition,the researchers observed a correlation between Rvolume and RCBF and DBAT in the frontal gray matter,parietal white matter,putamen and deep white matter brain regoins.Rvolume was significantly positively correlated with RCBF and significantly negatively correlated with DBAT.Conclusion Compared with the healthy control group,the stenosis of asymptomatic patients showed a significant decrease in cerebral blood perfusion and prolonged blood flow arrival time.Compared with asymptomatic patients and healthy controls,the stenotic side of symptomatic patients showed a more pronounced decrease in cerebral blood flow and a more pronounced increase in blood flow arrival time.Symptomatic patients had significantly lower volumes in several brain regions within the middle cerebral artery supplyed area compared to the other two groups.There was no significant difference in volume between asymptomatic patients and healthy controls.Correlation analysis showed a correlation between decreased blood flow and prolonged arrival of blood flow and changes in brain volume.A decrease in blood flow may accelerate the decrease in volume.A Study of Cognition and Brain Functional Connectivity in Patients with Asymptomatic Middle Cerebral Artery Severe Stenosis or OcclusionPurpose The aim of this study was to investigate and analyze the cognition and function changes in patients with asymptomatic atherosclerotic stenosis or occlusion of middle cerebral artery.Explore whether the disease condition of middle cerebral artery stenosis,might causes a decline in the cognitive function of the human brain and a decrease in the connectivity of human brain function.In previous studies,there hasn’ t been a research focus on the cognition and brain function changes of this type of patients.The experiment is innovative and practical.Materials and Methods We prospectively and continuously recruited patients with occasionally discovered atherosclerotic occlusive disease of middle cerebral artery(MCA)(which means severe stenosis(>70%)or occlusion of MCA)and healthy volunteers whose age,and education level were matched with the patients.Neuropsychological assessment methods such as the Mini-Mental State Examination(MMSE),Montreal cognitive assessment(MOCA)and other special assessment tests were used to assess cognitive and memory status of patients and healthy controls.The Z score of patients was calculated for further correlation analysis with the cerebral blood flow status.Imaging of resting-state fMRI was used to obtain the information of brain function of patients and controls,and was analyzed based on Matlab and Python platform.With the analysis,we could obtain the changes of functional connections of different brain regions of the whole brain,and acquired four connectivity parameters,strength,clustering coefficient,global efficiency and characteristic path length,through the graph-based analysis method.Brain structure imaging was performed using 3D T1-weighted MEMPRAGE sequence,and brain grey matter volume assessment of patient group and control group was performed with voxel-based morphometric measurement(VBM)analysis method.Meanwhile,all subjects were scanned with mTI-ASL sequence,and the CBF values BAT values in the bilateral middle hemisphere through all subjects were obtained by ROI delineation of middle cerebral artery territory.The neuropsychological scores,brain function connections,brain grey matter volumes and blood perfusion of the patients and healthy controls were statistically analyzed.Results The study enrolled 14 patients who met the inclusion criteria and 20 healthy volunteers for analysis.There were no significant differences in basic population and medical history between the patient group and the healthy volunteer group.There were also no differences in brain stenosis and white matter high signal scores and grades between the two groups.Meanwhile,the scores of the neuropsychological tests were not statistically significant between the two groups.Voxel-based morphological analysis also found no significant differences in brain grey matter volume between the two groups.Blood flow analysis showed that the CBF value of the stenotic side of the patient group was significantly lower than that of the contralateral side,and the BAT value was significantly longer than that of the contralateral side.Analysis of resting-state fMRI images showed a reduction in global brain functional connectivity in patients with asymptomatic MCA severe stenosis or occlusion.Functional connectivity between cortical regions was significantly reduced,and connections between the cortex and subcortical nuclei tended to decrease.The rules were most obvious in the frontal,temporal,and parietal regions,which is consistent with the blood supplying territory of the middle cerebral artery.The four connectivity parameters(strength,clustering coefficient,global efficiency and characteristic path length)based on graph theory analysis showed significant differences at 10 different thresholds compared to normal controls.Strength,clustering coefficient,global efficiency were significantly decreased(P<0.05),and the characteristic path length was significantly increased(P<0.05).Conclusion The results of this study showed that compared with healthy controls,in patients with asymptomatic severe stenosis or occlusion of the middle cerebral artery,the volume of grey matter in the stenotic side of brain did not change significantly,and there was no significant decrease in cognitive status of patients.It may not be appropriate for such patients to be treated with excessively aggressive invasive treatment.However,the cerebral perfusion of the stenotic side was reduced.And at the same time,in the analysis of brain function of resting state fMRI,it was found that the whole brain connectivity was widely reduced,the brain function network integration efficiency was low,the connectivity was poor,and was more isolated.As a result,different from patients with asymptomatic severe internal carotid artery stenosis or occlusion,cognitive function of this kind of patients might not decrease significantly.However,decreased brain function connectivity might be a signal for early changes in the brain of such patients. |
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