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Updated: Nov 29, 2025
Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla
Published on: February 19, 2021
Optimization of the refocusing flip angle in the characterization of cerebrospinal fluid dynamics using multi-spin
Tatsuhiro Wada1, Chiaki Tokunaga1, Osamu Togao2
1Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Purpose:
Multi-spin echo acquisition cine imaging (MUSACI) is a method used for cerebrospinal fluid (CSF) dynamics imaging based on the proton phase dispersion and flow void using 3D multi-spin echo imaging. In a previous study, the refocusing flip angle of MUSACI was set at a constant 80°. We conducted the present study to investigate the preservation the CSF signal intensity even in a long echo train and improve the ability to visualize CSF movement by modifying the refocusing flip angle in MUSACI.
Methods:
The MUSACI images were acquired in 10 healthy volunteers (7 men and 3 women; age range 24-44 years; mean age 29.4 ± 6.2 years) with a 3.0 Tesla MR scanner. Five refocusing flip angle sets were applied: constant 30°, constant 50°, constant 80°, pseudo-steady state (PSS) 50°-70°-100° (PSS50°), and PSS80°-100°-130° (PSS80°). In all sequences, the in-plane spatial resolution was 0.58 × 0.58 mm2, and the CSF movement for one heartbeat was drawn at 80-msec intervals. The signal intensity (SI) of CSF in the lateral ventricle, the foramen of Monro, the third ventricle, the fourth ventricle, and the pons was measured on MUSACI. Pearson's correlation coefficient was calculated between the CSF SI and effective echo time (TE; TEeff) in the lateral ventricle.
Results:
Both antegrade and retrograde CSF movements on the midsagittal MUSACI images and the retrograde CSF movement in the foramen of Monro was observed in all sequences with the constant flip angles. A strong reverse correlation between the CSF SI in the lateral ventricle and TEeff values was observed with constant 30° (r = -0.96, p < 0.01), constant 50° (r = -0.97, p < 0.01) and constant 80° (r = -0.88, p < 0.01). A weak positive correlation was observed with PSS50° (r = 0.28, p = 0.43), and a moderate reverse correlation was observed at PSS80° (r = -0.60, p = 0.07). The SI values of the foramen of Monro, the third ventricle, and the fourth ventricle were significantly lower than that of the lateral ventricle, and those values were higher than that of the pons in both the constant 80° sequence and the PSS 50° sequence.
Conclusion:
PSS50° could be the optimal flip angle scheme for MUSACI, because the SI changes due to CSF movement and the SI preservation due to a long echo train were large due to the use of the refocusing flip angle method.
