Application Of Olfactory Function Magnetic Resonance Imaging In The Diagnosis Of MCI And Early AD

Objective: There are differences in the activation of brain regions related to olfactory in inhaling pleasant odor(PO)and unpleasant odor(UPO),and currently no combining PO and UPO to assess mild cognitive impairment(MCI)and Alzheimer’s disease(AD).1 Applying and optimizing the olfactory fMRI technology.To analyze the differences of activation caused by PO and UPO in the whole brain and the region of interest associated with olfactory(ROIawo)in normal young people;2 After inhaled PO and UPO,compared the differences between the activation of the whole brain and ROIawo in the normal control eldly person(NC)and the difference between the young people and the NC,to estimate the effect of the age factor on the olfactory center,and to find the fMRI index reflecting the olfactory dysfunction of NC;3 Inhaled PO and UPO,compared the differences between the activation of the whole brain and ROIawo in NC,MCI and AD,to explore the relationship between them and clinical olfactory evaluation and behavior;to evaluate the diagnostic value of combining PO and UPO olfactory fMRI for the MCI and AD,to find functional imaging indicators that can diagnose early AD.Objects and methods:Olfactory normal young people(20cases,10 males,10 females)and NC(25cases,11 males,14 females).Using the Siemens Trio a Tim 3.0T magnetic resonance scanner,through the olfactory stimulator,applying event-related design to show olfactory stimulation.Select the bilateral primary olfactory cortex(POC),hippocampus and orbitofrontal cortex as ROIawo,to extract the number of activated voxels in each ROIawo.Inhaled PO and UPO,compared the differences in the activation of the whole brain and in the number of activated voxels per ROIawo.Compared the similarities and differences of olfactory fMRI between NC group and normal young group.MCI(26 cases,9 males,17 females)and AD patients(22 cases,9 males,13females),NC was used as control group.Accepted neuropsychological scale,olfactory subjective evaluation,apolipoprotein E ε4 allele,urine AD-related neurofilament protein tests.The olfactory fMRI is the same as the above.Inhaled PO and UPO,compared the differences in the activation of the whole brain and the number ofactivated voxels per ROIawo in the three groups.To analyze the correlation between the results of fMRI and the results of the three groups of subjects’ neuropsychological scale,olfactory subjective evaluation.Compared the similarities and differences among the three groups of behavioral data.Result:The activation of the whole brain was both similar in the normal young group,UPO was more obvious than PO(P=0.01).For NC,the activation of the whole brain was both similar to the young group,the activation range of whole brain was less than the young group.The activation of ROIawo in young group: at the POC(Z=-1.972,P=0.049)and frontal inferior orbit(Z=-2.167,P=0.03),there was a significant difference in the number of UPO and PO activated voxels,the former being greater than the latter;at the hippocampus and other orbitofrontal cortex,there was no significant difference(P > 0.05).The activation of ROIawo in NC: at the frontal inferior orbit(Z=-2.178,P=0.029),there was a significant difference in the number of UPO and PO activated voxels,the former being greater than the latter;at the POC,hippocampus and other orbitofrontal cortex,no significant difference(P > 0.05).The activation of ROIawo in MCI and AD:at all ROIawo,there was no a significant difference in the number of UPO and PO activated voxels.Stimulated the two kinds of odor,the activation range of whole brain showed a decreasing trend from NC to MCI to AD group.There was no significant difference in MCI group and AD group in all ROIawo.The activation of the POC in NC,MCI,AD under the different concentrations(0.10%,0.33%,1.00%): PO,with the increasing of the concentration,the number of activated voxels was increases after decreases in NC group and increasing trend in MCI and AD group;UPO,with the increasing of the concentration,the number of activated voxels was decreasing trend in NC group and increasing trend in MCI and AD group.Controlled the age factor,inhaled PO and UPO,there was a positive correlation between POC activated level and MOCA score in the three groups(r=0.277,r=0.342,P<0.05),and negatively correlated with olfactory recognition score(r=-0.391,r=-0.371,P<0.01);frontal inferior orbit activated level and MOCA score was positively correlated(r=0.227,P>0.05;r=0.331,P<0.05),and negatively correlated with olfactory recognition score(r=-0.412,r=-0.316,P<0.05).PO,there was no difference in the behavioral form for the three groups(χ2=5.681,P=0.058).UPO,there was a difference in the behavioral form for the three groups(χ2=31.275,P=0.000).The comparison showed:there were difference in NC and MCI(χ2=7.209,P=0.027),NC and AD(χ2=23.794,P=0.000),MCI and AD(χ2=15.520,P=0.000).Conclusion:In normal young people and NC,the activation range of the brain was more significant for UPO than PO.The activation range of the brain was smaller,prompt decreased olfactory function with age.Inhaled the two kinds of odors,there were differences at the POC and frontal inferior orbit in young group,but only difference at the frontal inferior orbit in NC,it may reflect the natural process of olfactory dysfunction.With contrast to NC,for MCI group and AD group,there were no differences in the number of activated voxels of the ROIawo,inhaled two kinds of odors,speculating that may be associated with AD pathological changes involved ROIawo.Inhaled PO and UPO,the difference in the number of activated voxels the frontal inferior orbit can be used as a biological indicator to distinguish NC and MCI.With the increasing of odor concentration,the activation pattern of POC showed that NC group had olfactory adaptation,while MCI and AD were not.Inhaled UPO,the activation pattern of POC can distinguish NC and MCI,can be used as detecting MCI biological indicator.Two kinds of olfactory fMRI are related to olfactory subjective scores and clinical scale,prompt PO and UPO olfactory fMRI can assess dysfunction and AD the clinical course.Inhaled UPO,the behavioral changes of respiratory regulation can reflect the degree of dysfunction,which provides a new direction for the clinical evaluation of olfactory function in the early diagnosis of AD.Above all,Compared to the simple PO olfactory fMRI,combined PO and UPO olfactory fMRI was more helpful for MCI and AD evaluation.