Changing Pattern Of Age-related Cerebral Glucose Metabolism In Healthy Individual Using ¹⁸F-FDG PET/CT

Objective The aim of this study was to evaluate the changing pattern of cerebral metabolism in aging healthy people using ¹⁸F-FDG PET/CT as a functional imaging modality combined with SPM analysis method,which can directly reflect the functional changes of the brain.The changing of glucose metabolism among normal aging healthy people in different age groups were summarized and analyzed,and the effects of aging on glucose metabolism of healthy brain were discussed,and an age-related standard database of brain glucose metabolism of normal people was established,so as to provide reference values and diagnostic criteria for¹⁸F-FDG PET/CT diagnosis of aging and nervous system diseases.Methods Brain ¹⁸F-FDG PET/CT images of 344 healthy subjects,who underwent ¹⁸F-FDG PET/CT in the Department of Nuclear Medicine,General Hospital of Ningxia Medical University from November 2014 to December 2018,were retrospectively included.Three hundred and forty-four subjects（age range:40-89 years old）were divided into 40-49 years old group,50-59 years old group,60-69 years old group,and 70-89 years old group.The position correction,normalization and smoothing of brain PET/CT images were performed with the statistical analysis software package SPM8 to make them correspond to the spatial coordinates of Talairach brain atlas.The SPM8 was also used to analyze the differences of glucose metabolism in different brain regions among different age groups,gender groups and left and right cerebral hemispheres.Statistical differences by XJview software areas of the brain stereotaxic analysis and quantitative analysis of voxel values,and calculate the metabolism to reduce or increase its proportion of the areas of the brain voxel values（voxel,l voxel values equal to 2 mm×2 mm×2 mm volume）.The FWE correction P values<0.05 level was considered as statistically significant.Results 1.The overall data and data of each group was processed,reconstructed and saved as a standard database.2.Data of different age group was compared with the baseline group（40-49 years old group）,and the FWE correction showed no significant decrease or increase in brain metabolism in each brain region before 60 years old at the level of P<0.05.However,after 60 years old,metabolic differences began to appear in the whole brain.The brain regions involved in decreased metabolism included bilateral temporal lobes,thalamus（dorsal medial nucleus）,parahippocampal gyrus,caudate nucleus,anterior cingulate gyrus and cerebellum.While,the brain regions involved in the increased metabolism included cingulate gyrus,lenticulate nucleus,thalamus（posterolateral ventral nucleus）,parietal lobe and bilateral frontal lobe.After the age of 70,decreased brain metabolism was associated with anterior cingulate gyrus,bilateral frontal lobe,caudate nucleus,thalamus,cerebellum,parahippocampal gyrus and uncunate gyrus,while increased brain metabolism was associated with lenticulate nucleus,thalamus,right occipital lobe,bilateral frontal lobe,left temporal lobe and insula.3.The data in all ages according to sex.The different gender subgroups of the overall data and each age group were also compared with baseline group.The results showed that the change of men’s cerebral metabolism appeared since the 60s.After the age of 60,the metabolism of bilateral frontal lobe,caudate nucleus and thalamus,cingulate brain were gradually decreased,while that of cingulate,lentiform nucleus and thalamus,parietal lobe,bilateral frontal brain were increased.After the age of 70,the metabolism of anterior cingulate gyrus,bilateral temporal lobe,caudate nucleus,thalamus,and cingulate gyrus were gradually decreased,while the metabolism of lenticulate nucleus,thalamus,anterior cingulate gyrus,bilateral frontal lobe,platinate nucleus and occipital lobe were increased.However,the changing pattern of brain metabolism in women was not totally paralleled with men.After 60 years of age,the metabolism of the left occipital lobe,cerebellum and thalamus were gradually decreased,while that of the lenticulate nucleus,right occipital lobe,thalamus,frontal lobe,platinate nucleus and insula were increased.After 70 years of age,the metabolism of bilateral frontal lobe,cerebellum and thalamus was decreased,while the metabolism of lenticulate nucleus,thalamus,right occipital lobe,bilateral frontal lobe,insula,right temporal lobe and anterior cingulate gyrus was increased.4.The overall changes of the whole brain metabolism showed a decreasing trend with the increase of age,and only a few brain regions showed an increasing trend.In addition,the decrease of metabolism in the right hemisphere was more significant than that in the left.5.The whole brain and the cerebral hemispheres in different gender subgroups were also compared,respectively.The whole brain metabolism decreased from the age of 60 in male,and showed an accelerating trend after 70 years old.While in women,the decrease was also observed from the age of 60,but the trend was slightly slow down after 70 years old.In addition,it was showed a faster downward trend of decreased metabolism in the left cerebral hemisphere than the right in both men and women from 60-69 years old,while the opposite trend was observed from 70-89 years old.Conclusion 1.With the increase of age,the changes of average glucose metabolism in the whole brain were mainly decreased.The decreased regions involved bilateral temporal lobe,bilateral frontal lobe,anterior cingulate gyrus,thalamus,caudate nucleus,parahippocampal gyrus and cerebellum.Besides,the metabolism of some other regions increased,including the lenticulate nucleus,thalamus,occipital lobe,bilateral frontal lobe,left temporal lobe and insula lobe.2.The decrease trend of brain metabolism is slightly different with gender,the decrease of brain metabolism began from the age of 60 and accelerated after age 70.In different sex groups,the decrease of brain metabolism in men began after age 60 and accelerated after age 70.In the female group,the decrease of brain metabolism began after age 60 and slowed down after age3.Regardless of gender,the overall trend of brain metabolic decline was more significant in the right hemisphere than in the left.Along aging,the decrease trend of metabolism in the left hemisphere was slightly faster than that in the right after 60 years old,and an opposite result was observed after 70 years old.