Sodium Invisibility in Single Quantum Sodium Imaging of the Human Brain

Rob Stobbe¹, Christian Beaulieu¹

An altered signal intensity dependence on prescribed flip angle is demonstrated for sodium projection imaging of the human brain in white matter regions, especially those with tracts predominantly running parallel to the static magnetic field. Relative regional signal loss on `non relaxation weighted` sodium images acquired with 90^o flip angles, as opposed to 53^o flip angles, is proposed to result from residual quadrupole spectral splitting in the highly ordered white matter fibres on the order of or greater than the RF pulse bandwidth. The associated signal loss is important to consider for quantitative tissue sodium concentration mapping.