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Application of 3T Magnetic Resonance 3D StarVIBE Sequence in Fetal Brain1West China Second University Hospital，University, Sichuan, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Sichuan, China, Chengdu, China, 2Siemens Healthineers, China, Shanghai, China
Synopsis
Fast T2-weighted imaging is a commonly used diagnostic sequence for fetal MR. Because of the limitations of fetal development, the imaging effect of T1 nervous system imaging is difficult to achieve like the post-natal image effect. The 3D StarVIBE sequence is used as a new sequence under 3T MR, using a radial K-space filling, not sensitive to motion, can be applied to the fetal nervous system examination. Recent reports suggest that the TurboFLASH(TFL) sequence with an optimized TI time of 2500 ms is used as an advantage of excellent contrast and overcoming motion artifacts in 2D gradient echo sequences. Therefore, this study will use the 3D StarVIBE sequence and the TFL sequence as a reference to judge its imaging effect.
Purpose
T1
weighted imaging as a basic sequence is critical in diagnosing fetal brain diseases,
while currently its research application at 3T is limited. This study aims to
improve tissue contrast by applying 3D StarVIBE to fetal neurological imaging
studies at 3T scanner.Material and methods
In this study, 32 cases of mid-late pregnancy (25 weeks of pregnancy - 38+1 weeks of pregnancy) were enrolled and underwent fetal-specific cranial examination using a 3T MR Scanner (MAGNETOM Skyra, Siemens healthcare, Erlangen, Germany). All fetal brain T1WI sequences were applied with 3D StarVIBE and TFL sequences. The basic scanning parameters of 3D StarVIBE were: TR/TE=3.86/1.65, FOV=350mm2, and total acquisition time=1:05min; the basic scanning parameters of TurboFLASH (TFL)sequence were: TR/TE=2900/2.54, FOV=380mm2, TI=2500ms, and total acquisition time=1:03min. This study covered following evaluations : 1) Multiple flip angles were set for 3D StarVIBE , namely 5.5 degrees, 9 degrees, 12 degrees, and 15 degrees, to determine the optimized flip angle with best contrast ; 2) StarVIBE sequence was compared with TFL sequence for their diagnosis performance; 3) The StarVIBE images with optimized flip angle were analysis in different gestational week, and confirm whether the gestational week impact the image quality; 4) The image were pointed scores in imaging quality and image artifact, including contrast and display of important anatomical structures such as basal ganglia, central groove, brain myelination, etc. The scores of images quality divided into five grades from 0 to 4. The scores of artifacts are divided into 4 grades from 0 to 3 scores.Results
By optimizing the T1WI 3D StarVIBE imaging of 3T scanner, the imaging time is comparable to that of TFL sequence. The results of image analysis are as follows: 1) flip angle significantly influenced the contrast and image quality of the T1 weighted image. A better image was obtained with a flip angle of 9 degrees: the contrast of gray matter was better than the flip angle of 15 degrees (P=0.0326) and the TFL sequence (P=0.0002); the contrast of myelination was better than the TFL sequence (P<0.0001). The showing of central sulcus was better than the flip angle of 15 degrees (P=0.032) and the TFL sequence (P=0.01); the showing of basal ganglia structure was better than the flip angle of 15 degrees (P=0.021) and the TFL sequence (P=0.0012); It was also found that the showing of myelination was better than the TFL sequence at all small angle flip angles of the StarVIBE e sequence (P<0.05); 2）The showing of anatomical structure and the image quality of the image were not gradually improved with the gestational age growth. 3）The imaging noise and artifacts of the 3D StarVIBE sequence at different flip angles were compared with the T1 weighted images acquired by the TFL sequence. It was found that the 3D StarVIBE sequence was better than the TFL sequence in artifact generation at 9 degree, 12 degree and 15 degree flip angles (P < 0.05); the difference in image between the StarVIBE sequence and the TFL sequence was not statistically significant in terms of noise generation.Discussion
The 3D StarVIBE T1 weighted imaging sequence g using 3TMR can obtain excellent T1-weighted images in a free breathing state, overcoming fetal motion and maternal breathing interference, and small angle excitation can produce better image quality. The optimal flip angle is the analysis and evaluation of the image quality after imaging by multiple angle settings, and finally statistical analysis is performed on the observation imaging capability level of multiple brain tissues, and the ability to overcome fetal and maternal artifacts is evaluated. The small flip angle 3D StarVIBE 's ability to overcome motion artifacts has also been confirmed, so it can provide a stable and effective T1-weighted image for 3T fetal nervous system examination, with a small flip angle of 9 degrees imaging as a preference, but its diagnostic performance is not obvious increase with the gestational age of the fetus.Acknowledgements
No acknowledgement found.References
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