Water-Specific Quantitative MRI Relaxometry of the Brain using Spatial-Spectral Water Excitation: Preliminary Experience

Methods: The mixed turbo spin echo pulse (mixed-TSE) sequence was implemented with second order binomial water-selective spatial-spectral excitation pulses (1), hereafter SSE-mixed-TSE (Figure 1). Mixed-TSE is a four time point pulse sequence that incorporates the principles of differential T1and T2-weighting in a single acquisition. By substituting the standard spatially-selective excitation pulses with binomial chemically-selective spatialspectral excitation pulses (Figure 1), a chemically specific qMRI pulse sequence results. As noted, a second-order binomial (1-2-1) pulse was employed for SSE-mixed-TSE consisting 22.5°-45°-22.5° spatially selective pulses interspaced by 2.3ms. Key imaging parameters: 40 slices/ 0.937x0.937x4.4mm/ 8,120msTE1, 2/ 700,4065msTI1, 2 and 8130msTR.