The Development Of The Fetal Lateral Ventricle And Its Relationship With The Calcarine Sulcus

Fetal brain development is an important part of fetal development.Abnormal fetal brain development will lead to the occurrence of neuropsychiatric diseases,resulting in adverse developmental consequences.With the rapid development of medical examination technology,ultrasound,MRI and other examination technologies have been widely used.The diagnosis rate of fetal malformation in pre-pregnancy examination increased significantly.At present,lateral ventricle has been proved to have a close relationship with fetal malformation.Lateral ventricle examination is listed as a routine program of fetal pre-pregnancy examination in clinical.The calcarine sulcus lies on both sides of the posterior horn of the lateral ventricle.It is a primary sulcus with constant position on the medial surface of the occipital lobe.There is a certain correlation between the position of the calcarine sulcus and lateral ventricle.This correlation has gradually attracted the attention of many researchers.Therefore,it is important to grasp the intrauterine development rules and the correlation between the lateral ventricle and calcarine sulcus,which is helpful to improve the diagnosis level of lateral ventricle abnormalities.Ultrasonography is widely used in the examination of fetal lateral ventricle because of its advantages of no radiation,economy and convenience.Many studies about lateral ventricle development have also been gradually carried out.Ultrasonography was used to measure lateral ventricle width and other two-dimensional diameter values.It was found that the value range of lateral ventricle width in normal fetuses was within 10mm.Therefore,the width of the lateral ventricle greater than 10mm were defined as the ventriculomegaly.Ultrasonography has some limitations in fetal lateral ventricle examination due to the problems of low resolution and motion artifacts.With the development of MRI technology,MRI examination of the lateral ventricle is required when the lateral ventricle width abnormality is observed by ultrasound,which significantly improves the diagnosis level of lateral ventricle abnormality.Then the study on lateral ventricle is getting deeper.High-resolution brain images about the lateral ventricle can be obtained by high field intensity MRI.Many scholars began to use image processing software to analyze the lateral ventricle and construct a three-dimensional model of the lateral ventricle.The volume and surface area of the lateral ventricle were analyzed.However,in vivo MRI still has some disadvantage such as motion artifact.The resolution of the images obtained by scanning is not enough to distinguish the boundary of some structures due to the limitation of scanning time.At the same time,the current studies on lateral ventricles mainly focus on the development analysis within a certain stage.The development law of lateral ventricles within a wide range of gestational age is unclear.With the application of post-mortem MRI with high field intensity,the acquisition of high-resolution images has become a reality.The related research results of brain structure have been confirmed in many studies.In this study,postmortem MRI with high field strength was used to study the development of the lateral ventricle.The problem of unclear structure display in image images caused by low resolution and motion artifacts is avoided,and the accuracy of the results is improved.The calcarine sulcus is located on both sides of the lateral ventricle occipital part on the medial cerebral cortex.The sulcus indicates the abnormal development of the surrounding cortex when the sulcus morphology is abnormal.The calcarine sulcus is one of the earliest primary sulcus on the medial surface of the brain.The study of the calcarine sulcus began with the observation and direct measurement of postmortem specimens.The study found that the calcarine sulcus began to appear at the 16th gestational week and confirmed the asymmetry of the calcarine sulcus development.With the application of intrauterine MRI,the image data of fetal brain was gradually obtained.Researchers began to use image processing software to conduct three-dimensional analysis on the development of sulci,which enriched the research on the cortical folding.The results showed that the calcarine sulcus appeared as early as 22 weeks of gestational age,which is significantly later than the neuropathological results.The study applied to the calcarine sulcus found that the occurrence of calcarine sulcus was advanced to the 15th gestational week because of the high resolution and no motion artifacts of post-mortem MRI with high field intensity.In the present study,the segmentation of the medial cerebral cortex of the fetal brain is restricted due to the presence of basal ganglia on the medial surface.There are few studies on cortical folding on the medial surface.At the same time,there is an obvious positional correlation between the calcarine sulcus and the lateral ventricle.In this study,postmortem MRI with high-field strength was used to study the development law of the calcarine sulcus.It was found that the left and right calcarine sulcus developed asymmetrically,which enriched the study of the medial cortical folding asymmetry.Abnormal changes in the morphology of lateral ventricles often indicate abnormal development of central nervous system.Thus,it is necessary to master the morphological evolution of lateral ventricles.The lateral ventricles develop from the prosencephalon,which appear to be round during vesicle period,then become thinner and narrower as they development.The changes of lateral ventricular morphology were correlated with the development of the subcortical structures around the lateral ventricles.In the second trimesters,the volume of basal ganglia,thalamus and other structures increased with development,while the volume of lateral ventricle relative to brain tissue decreased.In the late second trimesters,the cerebral cortex expands rapidly,and the absolute volume of the lateral ventricle also expands rapidly.It was found that the morphological evolution of lateral ventricle was not only related to the changes of the structures around the lateral ventricle,but also related to the folding of the medial cerebral cortex.Animal experiments have confirmed that the formation of lateral ventricles is closely related to the evolution of the calcarine sulcus.There was a negative correlation between lateral ventricle width and calcarine sulcus depth in fetuses with independent mild ventriculomegaly.In this study,postmortem MRI with high field strength was used to study the relationship between the lateral ventricle and the calcarine sulcus in normal fetuses,which will provide clues for the study of the relationship between the formation of the lateral ventricle and the surrounding structures.In view of the above problems,this study scanned fetal specimens within the wide range of gestational age with high-field intensity MRI.The obtained data were processed and analyzed.The developmental regularity and correlation of fetal lateral ventricle and calcarine sulcus were studied.Fetal brain structure has its own unique characteristics compared with adult brain.Fetal brain has been in the process of development,the structure is not mature and the development is fast.There is no image processing software suitable for the fetus.In this study,the method of manual segmentation is adopted to carry out structure segmentation,which avoided the segmentation errors that often occur in automatic segmentation.At the same time,the structure boundary in high field intensity MRI image is clearly displayed,which improves the accuracy of image segmentation and guarantees the accuracy of research results.It is of great significance to understand the development of intrauterine fetus to master the development rules and the correlation between the lateral ventricle and calcarine sulcus.The results will provide clues for the diagnosis and evaluation of lateral ventricle in clinical and enrich the research on the asymmetric development of medial cortex folding.This study is divided into three parts,summarized as follows:Part 1:The development of the fetal lateral ventricleObjectives:Fetal lateral ventricle development is an important part of brain development.Clarifying the development and evolution of lateral ventricle will provide the basis for the assessment of the lateral ventricle in the prenatal examination.The purpose of this study is to explore the morphological evolution of the fetal lateral ventricles during the second and third trimesters by reconstructing the lateral ventricles and conducting morphological analysis and quantitative measurement of the lateral ventricles.Materials and Methods:In this study,84 samples were included,ranging from 14 to 35 gestational weeks.The specimens were scanned by 3.0T and 7.0T MRI.Then the image data were imported into AMIRA software for image processing to construct a three-dimensional model of the lateral ventricle.The volume and diameters of the lateral ventricle were measured.The morphological evolution and diameters changes of the lateral ventricle were analyzed.Results:The lateral ventricle was immature at the 14 gestational weeks.Then it was gradually divided into four parts:anterior part,posterior part,central part and inferior horn.At last,it became narrow and thin.At the 33 weeks of gestational age,each part of the lateral ventricle became narrow and thin,tending to the adult form.The standardized volume of lateral ventricle showed a decreasing trend.The volume change of lateral ventricle was divided into two stages:stable period(14-23 gestational weeks)and fluctuating period(24-35 gestational weeks).The volume of lateral ventricle first decreased slightly during the 14-23 weeks of gestational age,then increased from the 24th week of gestational age,then increased to 4321mm3 at the 33 weeks of gestational age,and finally decreased to 2023.288mm3 at the 35 weeks of gestational age.The lateral ventricle diameter increased with gestational week.The value of LTAP increased the most,from 25.46mm to 52.28mm.Other values increased more slowly than LTAP,while LHCP is the slowest.The change of lateral ventricle diameter remained between 2mm-7mm,showing a slight increased trend.Conclusion:In 14-35 GW,the shape of the lateral ventricle changed from round to narrow and long,and finally developed into an adult shape.The change of the standardized volume of the lateral ventricle was consistent with the change of the morphology of the lateral ventricle.The lateral ventricular volume increased first and then decreased,which was consistent with the change of structures around the lateral ventricle.The length parameters of lateral ventricles increased with gestational week,reflecting the gradual enlargement of the structures around the ventricles.Among them,cerebral hemisphere changed the fastest,basal ganglia and thalamus change relatively slowly,corpus callosum basically has no change.The diameters of lateral ventricle remained stable within the range of 10mm.Part 2:The development of the fetal calcarine sulcusObjectives:The calcarine sulcus is a constant sulcus in the medial cerebral cortex.The development of the calcarine sulcus can provide clues for abnormal brain development.The purpose of this part is to provide the basis for elucidating the morphological evolution and asymmetrical development of the calcarine sulcus by analyzing the morphology,length,depth and the lateral differences of the calcarine sulcus in the second and third trimesters.Materials and Methods:A total of 93 specimens were scanned by magnetic resonance imaging(MRI)(3.0T and 7.0T)across a gestational age range from 14 to 33 weeks.The image data were imported into ITK-SNAP software for image processing.The three-dimensional model of the calcarine sulcus was reconstructed.The morphological changes of the calcarine sulcus were observed.The length and depth of the calcarine sulcus were measured.The changes of calcarine sulcus length and depth were analyzed with SPSS statistical software,and the lateral differences and morphological evolution rules of calcarine sulcus were finally explained.Results:Calcarine sulcus appeared at 14 gestational weeks and it was divided into 5 types with the increasing gestational weeks:continuous,flat,S-shaped,discontinuous and bifurcation.The length and depth increased with the increase of gestational weeks,and the length was less discrete than the depth.The depth and length of calcarine sulcus were expressed as follows,R-depth=0.401GA-1.224,L-depth=0.375GA-1.021,R-length=0.081GA2-2.265GA+19.401 and L-length=0.062GA2-1.594GA+13.327.The right calcarine sulcus length and depth were greater than the left.Conclusion:The morphological variation of calcarine sulcus began in fetal period.The calcarine sulcus depth increased linearly,and the length increased rapidly after a smoothing growth.The individual difference of the length was smaller than the depth,suggesting that the length was more stable and had more diagnostic significance than the depth in clinical diagnosis.The length and depth of right calcarine sulcus were greater than the left.The results were valuable to understand the development of calcarine sulcus and provided clues to the asymmetrical development of the fetal brain.Part3:Relationship between lateral ventricle development and calcarine sulcusObjectives:The lateral ventricle is closely correlated with the calcarine sulcus during fetal brain development.This part aims to explore the correlation between the lateral ventricle and the calcarine sulcus development.The results are conducive to revealing the relationship between the lateral ventricles and surrounding structures,which can provide a basis for the diagnosis of lateral ventricular abnormalities.Materials and Methods:Fetal brain MR imaging(3T and 7T)was performed in 84 fetuses at 14-35 gestational weeks.The three-dimensional models of the lateral ventricle and the calcarine sulcus were reconstructed under the same space.The morphological evolution and mutual position of the two structures were observed,the diameters was measured.The correlation between the positions and diameters of the two structures was analyzed.Finally,the statistical relationship between the diameters of the lateral ventricle and the calcarine sulcus was obtained by using SPSS software.Results:The sectional areas of the lateral ventricle became smaller with the development of the calcarine sulcus on MRI images.The calcarine sulcus was close to the posterior part of the lateral ventricles.On the lateral view,the calcarine sulcus and lateral ventricles overlapped before 21 gestational weeks.Then the calcarine sulcus gradually increased backward and exceeded the occipital part of the lateral ventricles,and the posterior part of calcainrine sulcus was wavy.A linear correlation occured between the calcarine sulcus length,depth and the posterior horn length;R-length=2.4204(LPH)-27.5706,R-depth=0.5145(LPH)-2.3072,L-length=2.0939(LPH)-23.4099 and L-depth=0.5902(LPH)-2.3403.Conclusion:The growth of the calcarine sulcus length accelerated noticeably after a slow developmental period,which was consistent with the variation of the lateral ventricle volume in 14-35 GW.The calcarine sulcus was located in the medial surface of the occipital part of lateral ventricle.The shrinkage in the lateral ventricle posterior horn was accompanied by the development of the calcarine sulcus,resulting in a better linear correlation between the calcarine sulcus length and the posterior horn length.The relevant results were helpful in understanding the evolution of the lateral ventricles and providing a basis for the diagnosis of lateral ventricle abnormality.