Normal Development Of The Fetal Spinal Canal And Spinal Cord At T12 On 3.0-T MRI

BackgroundThe development of the fetus is a process that follows a specific development laws and increases gradually from scratch.In the development of the fetus,many kinds of malformation can be caused by chromosomal variations.The Fetus can be died as the result of the Severe malformation.Early discovery and diagnosis of fetal dysgenetic malformation is conducive to early treatment of deformed fetuses and prognostic outcomes,and in order to be effective in choosing effective methods.The development of prenatal imaging techniques such as ultrasound and magnetic resonance(MRI)makes the possibility of early Accurate diagnosis of fetal malformation increases dramatically.Ultrasound is the preferred method to assess fetal central nervous system abnormalities.At present,the whole anatomical structure of the fetus can be examined in real time Ultrasound,and most of the fetal abnormalities can be diagnosed.Ultrasound are the most common methods for the clinical prenatal examination and evaluation of fetal malformation.Now with the development of 3D ultrasonic technology,we can add special probes and post-processing software on the basis of 2D ultrasound,so more and more 3D ultrasonic imaging technology is also used in clinical prenatal examination,which is an important complementary examination method for 2D ultrasonic doubt.But ultrasound tests are limited when the parent is obese,the amniotic fluid is too small[1].MRI is commonly used to examine the fetus that is suspicious of abnormity,as an important complementary examination method for ultrasonic examination,which can eliminate suspicious fetal abnormalities,avoid unnecessary anxiety and surgery,and supplement and revise ultrasound diagnosis,providing more detailed information on fetal dissection.Early discovery of prenatal spine and spinal cord malformation was able to choose an effective approach to early intervention.As the spinal cord structure of the fetus is relatively small,and the spinal bone is located around the spinal cord,the specificity and sensitivity of the spinal cord are not high,and the application of ultrasound in the diagnosis of spinal cord is limited.MR]development quickly,high resolution,without radiation.The development of the fetus,especially the development of the spine and spinal cord can be effectively showed by MRI.MRI was used for fetal examination in 1983.However,the use of MRI in the prenatal diagnosis is limited.With the development of MRI technology,it was possible to complete a sequence in a very short time,reducing the effect of the fetal motion,so then the MRI was widely used in the clinical prenatal examination,and became an important tool for the examination of the fetus.Although there is no report of damage to the fetus on MR]examination,the fetal MRI examination of the fetus is usually used in the late stage of pregnancy.1.5T and 3.0T MRI used in the late period of pregnancy is safe.The signal-noise ratio and spatial resolution of 3.0T MRI are higher,the structure of bone and cartilage can be more sensitive on 3.0T MRI,and then more and more 3.0T MRI are used in the diagnosis of fetus.Techniques such as the DWI are also used in the examination of the fetus[2,3].MRI examination can also be used as a method of checking for abnormalities that cause fetal death or neonatal death.Autopsy has been an important method to find the cause of fetal or neonatal deaths,but fewer and fewer parents now agree to autopsy.In particular,the autopsy of the fetal spinal cord is difficult,the spinal cord structure can be destroied by autopsy.Medical imaging has been an important complementary examination of fetal autopsy,which is easier to be accepted by fetal parents because of its uninvasive.In the past,the X-ray system was used to image the fetal skeletal system.X-ray imaging can visually display the overall condition and significant deformities of the whole skeletal system of the fetus,showing the relative size of different bones,but the small abnormalities cannot be showed by the X-ray image,and the condition of the intracranial and spinal canal can not be showed by the X-ray image.The fetal abnormalities and the relationship with the surrounding tissue can be showed by MRI imaging and the data can be stored permanently for future pregnancy counseling and research.MRI also has a good soft tissue resolution that shows the anatomical structure of the brain and spinal cord and other important organs,not to damage the fetal organs.It is an important alternative to the autopsy.After MRI,the body could be dissected in an abnormal area to obtain more accurate tissue anatomical diagnostic information.MRI and autopsy data can provide important information for the fetus or newborn parents to predict the risk of their next child with deformity.Understanding the development curve of the spine and spinal cord is beneficial to discover the abnormal development of them.CT is used to describe the development of the C4,T6,L3,C1-S5 vertebrae and their three ossification centers,to assist the diagnosis of fetal spinal deformity and evaluate the development of the fetal spine[4-8].CT has radiation,it can only be used for the study of bone development and deformity of fetal specimens.Fetal specimen MRI imaging was not limited by the time and the magnetic resonance field and the quality of imaging was significantly improved.With the development of MRI faster imaging technology,MRI is widely used in the imaging of the fetus,the quality of the fetal spinal cord imaging is improved.There have been more scholars using MRI to study the spine and spinal cord of normal fetal specimens.In 2006[9],there was a study of the spine area of the normal fetal specimen.30 specimens with the the gestational ages of 14-41weeks was studied.The height and area of lumbar 2 ossification center and vertebral body in lumbar 2,as well of the height lumbar 1/2 disk was studied.The results showed that the height and area of the lumbar 2 vertebral body and its ossification center have a good linely relationship with the gestational ages.The signal of lumbar disc changes with the gestation ages,and the growth rate of the disc is greater than the vertebral body.In 2012[10],6 normal fetal specimen of 20 weeks gestational age was studied.The results showed that the lumbar segment of the vertebral body was the largest.It is feasible to obtain the ossification process of the fetal spine on MRI.MRI had enough contrast to distinguish the bones and muscles.In recent years,there have been more studies in the area of spine and spinal cord in fetal specimens on MRI in China[11-15].The development of the lumbar sacral enlargement of the fetal spinal cord was studied.The diameter of the lumbar sacral enlargement was increased linearly with the gestational ages.The length of the normal fetal lumbar spine,the lumbar cord,the cervical cord grow linearly with the gestational ages.The development characteristics of C4 and its three ossification centers were studied,and the parameters of the results grow linearly with the gestational ages.The C4/5 disc had a good linear relationships with the gestational age.In 2018[16],the researchers studied the relationship between the twelfth pairs of thoracic nerve and the spinal cord.The position of the 12th thoracic vertebra were determined by the twelfth rib,and then identified the position of the 12th of the spinal nerve.The results showed that in the late stage of pregnancy,the Angle decreased with the gestational ages.The series of studies has greatly enriched our knowledge of the growth and development of spine and spinal cord in the fetus,and provides important reference data for the diagnosis of fetal spine and spinal cord disease,and also provides an important basis for MRI to determine whether the spine and spinal cord of the fetus is normal.There are few studies of the thoracic vertebra and spinal cord of normal fetal specimens on the MRI imaging.The purpose of this study was to show the development of the spinal canal and spinal cord at T12 on 3.0-T MRI.PurposeTo determine the normal appearance of the fetal spinal canal and spinal cord at T12 across different gestational ages using 3.0-T MRI.Material and MethodsThe spines of 43 normal human fetuses,aged 15-40 weeks,were scanned by 3.0-T MRI.All specimens were scanned using a GE 3.0-T MRI scanner.Imaging of the T12 vertebrae was performed in the coronal,sagittal,and axial planes.The anterior-posterior(AP)diameter,width,and cross-sectional area of the spinal canal and spinal cord at T12 were measured.The influence of gestational age on these parameters was investigated with a scatter plot and linear regression analysis using Pearson correlation coefficient.ResultsThe normal morphology of the fetal vertebra at T12 can be clearly showed by MRI;the spinal canal appeared circular,while the spinal cord was ellipsoid.Linear regression analysis showed a significant positive correlation between the AP diameter,width,and cross-sectional area of the spinal canal at T12 and gestational age.ConclusionPostmortem MRI is a reliable method for understanding the growth dynamics of the spinal canal and spinal cord at T12.Findings from this study would benefit the prenatal diagnosis of congenital malformations by MRI.