Aging Pattern Of The Brainstem Based On Morphology And The Construction Of Probabilistic Atlas Of The Brainstem

As an important link between the central nervous system and peripheral nervous system,the brainstem is the junction and common pathway between the hemispheres,cerebellum,and spinal cord,including the site of origin,termination,and relay center of many ascending and descending pathways.And the relationship between brainstem volume and neurological disorders has been revealed by numerous researches.Although the brainstem is an important nerve center of human beings,due to various difficulties,such as the deep position and complex structure of the brainstem,it is one of the most difficult parts for anatomy and surgical operation.In addition,in the imaging,it is difficult to distinguish the density of the nucleus in the brainstem,which is the "blind area" of many brain atlas,so the research on the brainstem has been in a laggard status.However,the development and application of magnetic resonance imaging(MRI)technology has changed this situation and provided a great help for brainstem studies,especially making large-scale neuroanatomical measurements in vivo becoming possible.Also,with the popularization of numerous image post-processing software,further standardization of images and comprehensive analysis of each imaged voxel have made it possible to study MRI instead of mere visual observation and manual measurements,and the results generated by standardization have made reproducible data from large sample sizes.This study is mainly composed of three parts.The first part discusses the effects of different intracranial volume correction methods on the measurement of intracranial structure.Before studying the morphological characteristics of the brainstem,choose the appropriate method to solve the related problems caused by individual differences.We used the structural MRI data of 140 healthy adults(age range:18-30 years old),used Freesurfer to automatically segment the brain region,and compared the images of intracranial structures measured by different correction methods.We found that the correlation coefficient between sex and intracranial volume was 0.537,and the correlation coefficient between intracranial volume and ROI was generally high,up to 0.883.The difference in most brain region volumes between male and female was due to the scale effect caused by sex independent intracranial volume.The residual method is one of the most accurate methods for intracranial volume correction.The second part is the study of aging pattern of adult brainstem based on morphology,measuring the volume,surface area and radial distance of brainstem at different ages to show the correlation between age and morphology.In this study,we investigated age-and sex-related differences in global,regional and local structural measures of the brainstem using the structural MRI data of 187 healthy adults(age range=18-70 years).Our results showed a significant negative age effect on volume of two major components of the brainstem-the medulla oblongata and midbrain.Significant age effects were not detected on the surface area and local morphological features of the brainstem,suggesting these structures may be relatively stable during the normal aging process.No significant sex differences and sex-by-age interaction on brainstem structural measures were found.The brain stem shows a flattening trend in the aging process.The third part is the construction of brainstem standard coordinate system and probability atlas of different age groups.There will be some changes in the brainstem during aging.It is difficult to accurately describe the brainstem positions and its internal structure using the MNI coordinate system.Therefore,we first defined a standard brain stem coordinate system to solve the inaccurate positioning of the brainstem position under the MNI coordinate system.Then we used the structural MRI data of 187 healthy adults(age range:18-70 years old)and divided them into five age groups.For each age group,SPM tools were used to construct the brainstem MNI coordinate system atlas and the brainstem standard coordinate system atlas.Different types of brainstem atlas were used to adapt to different application scenarios.This study enriches and improves the neuroimaging study of the brainstem and provides an anatomical reference for neurodegenerative diseases related to the brainstem,and these fundamental works may shed a light on the future research and clinical applications of the brainstem.