MRI study on the normal fetal development of cervical, thoracic and lumbar spines in specimens

Objective To assess the change rules of fetal cervical, thoracic and lumbar spinal volume and centrum volume with gestational ages. Methods The 3.0 T MRI was performed on 55 fetal specimens ranging from 17 to 42 gestational weeks with sequence of three dimensional T2WI. Among 55 samples, 20 samples were obtained from spontaneous abortion of pregnant women and 35 samples were obtained from induced labor of mothers due to serious diseases. The fetal specimen was derived from sectional imaging anatomy research institute of the medical school of Shandong University. No spinal abnormalities were found on CT scans. The cervical, thoracic and lumbar spinal volume was obtained by delineating the vertebral body contour on the reconstructed cross-sectional image with the OsiriX software (www.osirix-viewer.com). And the volume of the cervical, thoracic and lumbar spine was divided by the number of the vertebral bodies to obtain the centrum unit volume. Five lumbar vertebral bodies were measured one by one. Regression analysis was made between the volume of cervical, thoracic and lumbar spine and gestational weeks, and between the volume of lumbar vertebral bodies and gestational weeks to analyze the growth rule of spine. Results (1) The cervical, thoracic and lumbar spine volume increased linearly with gestational ages, and the linear regression equation was as follows: cervical spine volume (mm3) =-1 260.937+81.235×gestational week (R2=0.974, P<0.05), thoracic spine volume (mm3) =-5 933.521+347.503×gestational week (R2=0.972,P<0.05), lumbar spine volume (mm3) =-5 130.912+294.473×gestational week (R2=0.976,P<0.05). (2) The order from large to small of fetal spinal growth rate was thoracic, lumbar and cervical segment. Within the same gestational age, the order from large to small of spinal volume was thoracic, lumbar and cervical segment. The order from large to small of centrum unit volume growth rate was lumbar, thoracic and cervical vertebrae. (3) The volume of each lumbar vertebral body also increased linearly with gestational age. Conclusion The cervical, thoracic and lumbar volume show a good correlation with the gestational weeks in the second and third trimester fatal specimens, and the growth rate of different segments is different. Key words: Fetus; Spine; Bone development; Magnetic resonance imaging