On the use of a spin-echo based double inversion recovery acquisition for the measurement of cortical brain thickness

To determine whether a spin-echo-based sequence, which are inherently insensitive to magnetic field inhomogeneity, can be used for brain cortical thickness measurement studies.

By using a double inversion recovery (DIR) spin-echo-based sequence, cortical thickness estimates were performed from data acquired from seven healthy volunteers. The cortical thickness was also calculated from data acquired using an MPRAGE sequence and the Bland-Altman analysis was performed for comparison of the two methods. The average signal and contrast to noise ratios (SNR, CNR) of the two methods were also calculated.

The bias over the entire brain between DIR and MPRAGE was 0.87 ± 0.08 mm. The bias calculated in the major regional lobes were temporal: 0.76 ± 0.09 mm, frontal: 0.89 ± 0.07 mm, parietal: 0.92 ± 0.10 mm, occipital: 0.75 ± 0.12 mm, and cingulate: 0.79 ± 0.10 mm. This thickness difference was due mainly to the boundary difference in the MPRAGE and DIR at the grey matter/cerebral spinal fluid (GM/CSF) regions. The mean SNR and CNR was CNR(MPRAGE) = 47.8 ± 8.4 and CNR(DIR) = 19.2 ± 2.9, SNR(MPRAGE) = 76.8 ± 10.5 and SNR(DIR) = 21.1 ± 2.8.

The study suggests that cortical thickness measurements can be performed using a DIR spin-echo sequence, which is inherently immune to main field inhomogeneity. Larger thickness measurements were consistently observed in DIR compared with MPRAGE.