Simultaneous 3D acquisition of H-1 MRF and Na-23 MRI

Purpose To develop a 3D MR technique to simultaneously acquire proton multiparametric maps (T-1, T-2, and proton density) and sodium density weighted images over the whole brain. Methods We implemented a 3D stack-of-stars MR pulse sequence which consists of interleaved proton (H-1) and sodium (Na-23) excitations, tailored slice encoding gradients that can encode the same slice for both nuclei, and simultaneous readout with different radial trajectories (H-1, full-radial; Na-23, center-out radial). The receive chain of our 7T scanner was modified to enable simultaneous acquisition of H-1 and Na-23 signal. A heuristically optimized flip angle train was implemented for proton MR fingerprinting (MRF). The SNR and the accuracy of proton T-1 and T-2 were evaluated in phantoms. Finally, in vivo application of the method was demonstrated in five healthy subjects. Results The SNR for the simultaneous measurement was almost identical to that for the single-nucleus measurements (