Short Echo-Time fMRI using Magnetization Transfer Contrast

Jenni Schulz Presenter
Donders Institute, Radboud University
Nijmegen, - 
Oral Sessions 
Magnetization Transfer (MT) [Wolff1989] is an MRI technique generating contrast in the presence of molecules with bound protons. While brain tissue is known to show an MT contrast (MTC), blood does not display such behavior [Balaban1991]. Hence, an MT-weighted signal may be sensitive to cerebral blood volume (CBV) changes, with a maximum at echo-time TE=0. By contrast, most fMRI studies rely on Blood-Oxygenated Level Dependent (BOLD) experiments, whose optimal sensitivity is obtained at TE~T2* (30ms at 3T). Changes in CBV during brain activation can be expected to occur mainly in the arterioles and capillaries [Kim2006], and may therefore be expected to have a better spatial localization than BOLD, which is dominated by the downstream vasculature. Previous investigations into enhancing BOLD with MT have used off-resonance MT combined with long TR [Zhou2005] or inversion recovery [Song1997] which preclude efficient fMRI studies. Here, it is shown that an acquisition using on-resonance MT preparation can be sensitive to the hemodynamics induced by brain activations at short TE, which maximizes the sensitivity to CBV and reduces BOLD contamination, without increasing acquisition time.