The Development Of Spine In Fetus Using Postmortem MRI

PART I Study of correlation between the fetal spine length at different segments and gestational age and sexual dimorphisms with postmortem MRIObjectiveUsing the magnetic resonance imaging(MRI) to measure the length of cervical, thoracic,lumbar,sacrococcygeal segment of normal fetal spine at different gestational ages (GA), to study the correlation between the length of normal fetal spine segment and gestational ages and sex dimorphisms,analyze the developmental pattern.Materials and methodsThis research is a prospective study, Postmortem MR imaging was performed on 65 fetuses ranging from 16 to 42 gestational ages. The 60 human fetuses which showed normal on MR examinations were selected.3D-T2WI of the whole spine was performed in sagittal planed and then to obtained the images which reconstruct based on C4,T6,L2,S2 centrum in the coronal,sagittal and axial section, the sagittal section was used to perform the measurement of the length of the cervical,thoracic,lumbar, sacrococcygeal segment of spine, Lastly the relationship among these values with GA and sexual dimorphisms was analyzed statistically.ResultsA statistically significant linear relationship was established between the lengths of cervical,thoracic,lumbar,sacrococcygeal segments of spine and GA, the relationship were described by the functions respectively as:Cervical length (cm)=0.193+0.117 XGA, R2=0.94, P<0.05;Thoracic length (cm)=-0.761+0.272×GA,R2=0.98, P<0.05; Lumbar length(cm)=-0.401+0.147X GA, R2=0.98, P<0.05; Sacrococcygeal length (cm)=-0.646+0.158 X GA,R2=0.96,P<0.05. The development of every segments of spine is imbalance, there are two peaks during growth stages, they are 23-26GA and 31～34 GA respectively.The growth patterns of C4,T6,L2,S2 also fellow this trend, Sexual dimorphisms was not detected.ConclusionsThe fetal spine segment length increased linearitily with GA and sexual dimorphisms was not found. Therefore the spine length might can be used to assess morphologic maturity of fetuses.PART II Study of correlation between the development of ossification centers of fetal spine and gestational age with postmortem MRIIntroductionThe malformation of spine is one of the commonest congenital malformation and its pathological changes associated with many diseases. Therefore, the development of spinal is an important part in the prenatal routine examination. The better understanding of the spine development process could be a reference for abnormal prenatal detection. Previous studies mainly rely on ultrasound and X-ray equipment. The advantages of ultrasound make it is the first choice for screening in the clinical examination but its low tissue contrast and spatial resolution cannot meet the requirements of the clinical diagnosis. And X-rays, with the risk of radiation, can only distinguish ossification center of spine. As a non-invasive without radiation exposure technique, MR became popular tools for the research of assessing and monitoring fetal development. However, the question of when the ossification center of atlanto-axial vertebrae and Sacrococcygeal vertebrae appears and could be detected by MR in human fetuses hasn’t been fully answered. In order to address this question, we used the three-dimensional T2-weighted MR imaging technique to investigate the development process of ossification center in postmortem fetuses.ObjectiveUsing the magnetic resonance imaging(MRI) to describe features of the ossification centers of the craniovetebral junction and Sacrococcygeal region of normal fetal in second and third trimester of pregnancy.Materials and method65 post-mortem fetuses (GA 16～42weeks) were collected in hospitals of Shandong Province. The MR images were collected on a 3T MR scanner. The 60 human fetuses with normal anatomical structures on MR examinations were selected. The craniovetebral junction and Sacrococcygeal region of each fetus were scanned by using 3D T2-weighted imaging, Then the MR images were reconstructed in three orthogonal views. So that the ossification centers could be observed from different views. The candidate regions for detecting the development of the ossification centers including:lateral masse, anterior and posterior arch of the atlas, centrum, neural arches, the dens of the axis and Sacrococcygeal Vertebra.ResultsOn 3.0 T MRI, atlas consists of lateral masse, anterior and posterior arch during the development of fetus.Atlas consists of two ossification center(OC).The ossification center of C1 lateral masse could be detected on MR images as early as 16 weeks of gestational age (GA). The anterior and posterior arches are completely cartilaginous even at the end of the fetal stage. Axis consists of three or four ossification center.The ossification center of centrum and neural arches of the axis could be found as early as 16 weeks of GA, the dens is ossified about in the 18weeks of GA and the appearance rate could be 100% after 22 weeks of GA. The synchondrosis between the dens and the axis body has not fused at the end of fetal stage. The ossification center of S1～S3 could be detected on MR images as early as 16 weeks of GA. The first coccygeal vertebra ossification center could be found as early as 25 weeks of GA The ossification center of S5 and the first coccygeal vertebra appear percent is 100% at 22 and 30 weeks of GA, The areas of the ossification nuclei increased with the number of GA.ConclusionsBy using high spatial resolution T2-MRI, the changes of the ossification center of atlas, axis and Sacrococcygeal Vertebra during fetus developing could be observed clearly.The results demonstrated the relationship between GA and the development of spine structures which follows a specific spatio-temporal rule. The OC of the dens and the S5 appear percent is 100% after 22 GA, The emerge time of the ossffication center of the above structures could be a good sign for determining the fetal age.