The role of classic spin echo and FLAIR sequences for the evaluation of myelination in MR imaging.

Purpose: The aim of this study was to assess the features of the normal brain development in terms of myelination in infants and young children on fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging, and to determine if FLAIR imaging is superior to spin echo MR sequences.

Materials And Methods: T1-weighted (T1W) fast spin echo T2-weighted (FSE T2W), and FLAIR images were obtained in 76 pediatric patients between the ages of 0 and 48 months, on a 1 Tesla MR unit. On these images, the signal intensities of 16 different white matter regions were compared to those of adjacent gray matter, and for each brain region. Comparisons between the gray and white matter signal intensities were scored by the consensus of two radiologists on a scale of -1 to +1 for each patient.

Results: In the first 6 months, hypointense white matter signal intensity changed to hyperintensity on T1W images. After the first 6 months, white matter progressed from hyperintense to hypointense on T2W images. Except for the cerebral white matter, FLAIR images showed the same signal transition, though slightly later than what was seen on T2W images. The deep cerebral white matter, which was hypointense on birth, became hyperintense early in the first several months of life, and finally, reconverted to hypointense during the second year of life on FLAIR images.

Conclusion: Myelination, which is an indicator of brain maturation, was successfully demonstrated both in classic spin echo sequences and on FLAIR images. These imaging techniques are an essential component of routine MR imaging of the dating of and differentiation between normal and pathological brain development.