Alpha correction - Harris et al. JMRI 2015

• Correcting for different amounts of CSF is mathematically trivial due to its negligible GABA concentration.

• This assumption corresponds to WM having a GABA concentration that is half that of GM, a common assumption. 

• Consistent with the literature, calculating a from the current dataset results in alpha = 0.43

• Based on this value, the literature and our simulations, which show that it is better to overestimate rather than underestimate a, we round this value to 0.5.

• GABA values are often contaminated by 50% co-edited MM signal

• (Concentration of GABA in GM > WM > CSF)

Neonatal T1w/T2w image (contrast inversion) - Oishi et al. Magn Reson Imaging Clin N Am. 2012

• The neonatal brain is immature. On T1-weighted images, the intensity of the white matter is lower than that of the gray matter. On T2-weighted images, the intensity of the white matter is higher than that of the gray matter. These contrasts are the reverse of those seen in adults [Fig. 1]. This is caused by the incomplete myelination in the white matter of the neonatal brain. Because of the variability of the myelination status in different fibers, the contrast between the gray and white matter in some areas is very poor

• Because the white matter appears as hyperintense on newborn T2-weighted images, the rapid shortening of T2 in the white matter results in “contrast inversion” between the white and gray matter during postnatal development.

T2 correction