Early Development Of The Central Sulcus In The Fetal Brain Using High Field Magnetic Resonance Imaging

The development and maturity of the fetal brain, which develops fast and changes significantly, involve many parallel structures, including mainly the migration of nerve cells, the formation of sulcus and gyri, and myelinization of the furrow. Sulci appears earlier than gyri, and it can also be used as a marker of brain in different developmental stages. CS(central sulcus), one of the earliest-developed cerebral sulci of fetal cerebral cortex, is regarded as one of the most important areas by almost all the fetal cerebral cortex researches in the light of the importance of its front and post area structures and functions, and has great significance to clinical diagnosis of fetal diseases and prenatal and postnatal care.Visual method was used to observe and describe the forms and the development of CS and adjacent cortex by studying the early development of CS of fetal brain specimens when the medical imaging technology was not advanced.Despite the fast development of ultrasonic technology, the study on fetal CS shows that fetal cerebral sulcus found by ultrasonic was much later than the one observed in anatomy because of spatial resolution, tissue resolution and gases. The application of MRI (magnetic resonance imaging) used in fetal brain offers a noninvasive and higher resolution research method of fetal brain. MRI of fetal brain of specimen provides clearer MRI than that in vivo scanning because it can overcome unfavorable effects of fetal movement in the womb, maternal respiratory and visceral movements and parent structure. It has become the first choice to use MRI of fetal brain of specimen for the study CS in fetal cerebral cortex. Moreover, high-strength field MRIs can provide clearer imaging of CS.There was a great difference in the appearance time of CS in the past studies, while most of the existing specimen studies have not been systematic but only descriptive in the early development of CS, through which it is impossible to carry out retrospective studies in the future. Among the studies of this kind, the appearance time of CS is recorded in large varieties from 15nd to 27nd weeks of gestational age (GA). The reason why there is such great difference in the time is perhaps because of the different calculation methods of GA, different study methods, different standards of judgment and different resources of images, especially the readability of the images. In addition, the racial differences between Chinese and Westerners may also be responsible for the time difference of CS appearance. There have been many studies on the brain side and gender differences, most of which have proved the existence of side and gender differences. But there has not been a unified conclusion when human brain begins to develop and appear.The problems with the previous study on fetal CS are as follows: Firstly, most related imaging resources of descriptive study on fetal CS have not been kept. Even if there are the images of fetal CS, they are not suitable for study and analysis under visual conditions from different perspectives; secondly, quantitative analysis method was not applied to the study in the early development of fetal CS, which fails to form a systematic and consistent data of fetal CS and cannot be analyzed, so that the quantitative criteria could not be developed to decide the appearance time of fetal CS statistically; thirdly, there isn’t enough research on whether there exist the inter-hemispheric asymmetries and gender dimorphism in the early period of fetal CS.In the light of the reasons and questions mentioned above, this study scanned 7.0T high field-strength MRI of specimens of the fetal brain, covering from 11th to 22nd weeks of GA in order to obtain clearer section images of the development of fetal cerebral cortex. Three-dimensional images of fetal brain of all the weeks of GA are reconstructed with the help of image process software so as to set up a better visual platform for the early development of CS and to show the trend of the early morphological changes of the CS. Related data of every week of GA are measured with the help of image process software in order to obtain the consistent data of the early development of CS. Data standards are established of the appearance time of fetal CS. Related data of left and right sides of CS as well as of males and females from 11th to 22nd weeks of GA are acquired by the image process software in order to judge statistically whether there are the inter-hemispheric asymmetries and gender dimorphism during the early development of CS. This research sets up a visual platform for the research of the early development of CS for the first time, and acquires related data of the early development of CS for the first time. Quantified standards to judge the appearance time of CS are established, meanwhile, the results of whether the inter-hemispheric asymmetries and gender dimorphism exits during the early development of fetal CS are gained. This research will greatly enrich the data of the early development of fetal brain by providing reliable anatomical basis for clinical diagnosis and eugenics.This study consists of three parts, with the part one being about the visual research of fetal brain from 11th to 22nd weeks of GA, part two about the biometry of fetal brain from 11th to 22nd weeks of GA and part three about the study on the side and gender differences of fetal brain from 11th to 22nd weeks of GA.Part one:Visual study on the early form of central sulcus based on high field-strength fetal brain MRIObjectives:The study aims to establish a visual platform for the research of the early development of CS based on 7.0T high field-strength MRI of fetal brain of specimens whose GA cover from 11th to 22nd weeks of GA, and to reconstruct the three-dimensional forms of fetal CS.Materials and Methods:Sixty-five Chinese fetal specimens of normal brain development whose GA covered from the 11th to 22nd weeks of GA were available for this study. Forty-five of them were carefully selected finally for this study under the consideration the related information of pregnancy record, ultrasonic inspection record and information by 3.0T MRI. Cerebral MRI of the forty-five fetuses on 7.0T MRI are all acquired, the best fetal brain section image of which are put into Amira4.1 software to reconstruct the three-dimensional forms of fetal cerebral cortex visually. After the CS is located on the reconstructed 3D shape of fetuses, a visual platform is to be established for the research of the early development of CS and early development of fetal cerebral cortex from the 11th to 22nd weeks of GA, and then to analyze the characters of CS changes during this period of time.Results:7.0T high field-strength MR images of fetal brain from 11th to 22nd weeks of GA are acquired to reconstruct three-dimensional images of fetal cerebral cortex from the 11th to 22nd weeks of GA and to establish a visual platform for the research of early development of CS. The study on the lateral side of fetal brain on this platform shows that the consistence of CS appears on the same part from the 13th week to the 22nd weeks of GA. In spite of different forms, they stabilize near the sign line. The form of CS from the 13th week of GA is not stable, showing the active development of cerebral cortex during this period of time. CS exits clearly after the 15th to 16th week of GA. Another great change takes place around the 18th week of GA with certain depth and greatly extended length. From the 21th to 22nd week of GA, CS has the stable form with few changes of length and dept, and the precentral sulcus and postcentral sulcus appear on the front and back area of CS. With the development of CS in this period, the general form of CS takes a straight-line form and most parts of the CS are not connected with lateral sulcus.Conclusion:In the study, the visual study on CS shows that fetal CS has appeared at the 13th week of GA, which is earlier than what the previous research results showed. This study systematically shows the form change of early CS for the first time, which enriches the data of fetal cerebral cortex. Clear fetal specimen images acquired by high-field magnetic resonance can show the occurrence and early development of CS on the reconstructed fetal brain surface, which fully shows the significance of fetal CS visualization to the study on the occurrence and early development of CS.Part Two:Metrological study on the occurrence and early development of central sulcus based on high field-strength fetal brain MRIObjectives:The study aims to establish metrological data for the research of the early development of CS based on 7.0T high field-strength fetal brain after the fetal brain specimen scanning from 11th to 22nd weeks on7.0T MRI, and to explore the establishment of quantitative standards of CS appearance time in the early development by using statistics methods and analyzing the characters of early development of CS.Materials and Methods:Forty-five Chinese fetal specimens from the 11th to 22nd weeks of GA were available for this study, whose MRIs of fetal brain were acquired by 7.0T high-strength field scanner. The 7.0T T2WI of distinctive cerebral cortex and cerebrospinal fluid of each specimen are imported into Amira4.1 image process software to reconstruct the three-dimensional shape of the fetal brain. A visual platform is to be established for the research of the early development of CS and early development of fetal cerebral cortex from the 11th to 22nd weeks of GA.After the locating of the CS on the reconstructed outer side of fetuses, the maximum depth and length of CS in each week of GA are acquired with the help of measurement tools of Amira4.1. After the statistical processing and analysis of the characters and change trend of early development of CS, this study attempts to find the relatively slow period of development, on the basis of which quantitative standards to judge the time of CS appearance are explored.Results:The maximum depth and length of CS from the 13th to 22th weeks of GA are acquired. Statistical analysis shows that the first period of fast development of the maximum depth of CS occurs in the 14th to 15th week of GA (p<0.01), the second in the 16th to 18th week of GA (p＜0.01).The first period of fast development of the maximum length of CS occurs in the 13th to 14th week of GA(p＜0.01), and the second in the 16th to 18th week of GA(p＜0.05). The 15th to 16th week of GA is a period of stability after the first period of fast development, which may be called plateau period. The maximum depth and length of CS in the 15th week of GA can be used as measurement standards to judge the occurrence of CS. The mean value of the maximum depth and length of CS in the 15th week of GA stands at 0.23cm and 1.12cm respectively.Conclusion:On the visual platform based on high-strength field MRIs, biometrics is adopted to acquire related data of the early development of CS. Statistical analysis is used to judge the period of the fast development and plateau. Data of CS in the first plateau period of development are used as standards to judge the occurrence of CS, that is, the maximum depth and length of CS in the 15th week of GA can be used as numerical standards to judge the occurrence of CS. It is the first time for the study to try to establish the quantitative standards to judge the occurrence of CS, which enriches the data of fetal cerebral cortex and is of great significance to the study on the occurrence and early development of CS.Part Three:Study on inter-hemispheric asymmetries and gender differences of central sulcus based on high-strength field MRIObjectives:The study aims to acquire related data of the inter-hemispheric asymmetries and gender differences of CS after the study of the CS of fetal specimens from the 11th to 22nd week of GA on 7.0T MRI; and to judge preliminarily the inter-hemispheric asymmetries and gender differences in the early development of CS so as to enrich the data of the early development of fetal brain.Materials and Methods:Forty-five Chinese fetal specimens from the 11th to 22nd weeks of GA were available for this study, whose MRIs of fetal brain were acquired by 7.0T high-strength field scanner, and imported into Amira4.1 image process software to reconstruct the cerebral cortex 3-dimensionally. After the locating of the CS on the reconstructed outer side of fetuses, the maximum depth and length of different sides and the gender of CS in each week of GA are acquired with the help of measurement tools of Amira4.1 image process software, and after being processed statistically, they are used to judge whether there exists the side and gender differences of CS in the early development.Results:The maximum depth and length of different sides and genders of CS from 13th to 22nd weeks of GA are acquired.The result shows that there is significant difference (P＞0.05) after the analysis of the data differences between two groups of the maximum depth and length of different sides of CS in each week of GA, and the result also shows that there is significant difference (P＞0.05) after the analysis of the data differences between two groups of the maximum depth and length of different genders of CS in each week of GA.Conclusion:On the visual platform based on high-strength field MRIs, biometrics is adopted to acquire the related data of different sides and genders in the early development of CS (from 13th to 22nd week of GA). Statistical analysis is used to prove that there are not the inter-hemispheric asymmetries and gender differences in the early development of CS, which is of great significance to the study on the early development of CS and on the inter-hemispheric asymmetries and gender differences. It is the first time for the study to prove that there are no inter-hemispheric asymmetries and gender differences in the early development of CS (from 13th to 22nd week of GA), which enriches the data of fetal cerebral cortex and will lay a solid foundation for the research on the appearance time or GA of the inter-hemispheric asymmetries and gender differences in the early development of CS.