Susceptibility weighted imaging in evaluation of the fetal vertebra and vertebral anomalies

Objective To explore the advantages of susceptibility weighted imaging (SWI) in depiction of normal fetal vertebra and vertebral anomalies. Methods This prospective study was approved by our institutional review board, and written informed consent was obtained from every participant,Fifty-eight pregnant women (gestation age 22 to 39 weeks, average 29±3 weeks) who were suspected of carrying babies with vertebral anomalies by ultrasound screening underwent 1.5 T fetal spine MRI[including half-fourier acquisition single-shot turbo spin-echo(HASTE), true fast imaging with steady-state (True FISP) and SWI sequences]. MR images were reviewed for their quality by two radiologists independently. The image scores in HASTE, True FISP and SWI were compared by using Kruskal-Wallis test and Mann-Whitney U test. Three segments (cervical, thoracic and lumbosacral segments, respectively) of 15 fetuses were, at random, collected to compare among HASTE,True FISP and SWI and then evaluated by ANOVA analysis.The diagnostic accuracy of the three sequences among 32 cases with follow-up results was calculated respectively and compared by using Chi-square test. Results There was statistical differences among three sequences(χ2=50.685,P 0.05).A total of 32 fetal vertebral anomalies were identified by follow-up after birth including hemivertebra (n=14), fusion of vertebrae (n=1), butterfly vertebra (n=1),multiple vertebral malformations (n=9),spinal bifida (n=5),caudal regression syndrome (n=2). The diagnostic accuracy of SWI, True FISP and HASTE was 93.75% (30/32), 56.25% (18/32) and 37.50% (12/32) respectively. The diagnostic accuracy of SWI was the best compared to that of True-FISP and HASTE (χ2=10.083, 20.017;P<0.01). Conclusion SWI proved to be the optimal technique in depiction of fetal vertebra and vertebral anomalies than True FISP and HASTE, especially in depiction of cervical vertebra. Key words: Fetus; Spine; Congenital abnormalities; Magnetic resonance imaging; Susceptibility weighted imaging