MR Spectroscopy of Arbitrarily Shaped Single Voxel Using Half-Fourier 2D-Selective RF Excitations Based on a PROPELLER Trajectory

The measured signal in conventional single-voxel proton MR spectroscopy (MRS) is generated by three orthogonal slice-selective excitation pulses. This localization method limits the region of interest to cuboidal shapes. 2D-selective RF (2DRF) excitations [1] can be used to excite arbitrarily shaped regions of interest matching the shape of the target region in order to maximize SNR and minimize partial volume effects [2, 3]. In this work, MRS with segmented 2DRF excitations based on a PROPELLER-Trajectory [4] is presented. The trajectory consists of segments of parallel lines which are rotated to one another called blades. Spatially selective refocusing pulses after each segment are used to eliminate signal contributions from side excitations. The combination of the half-Fourier method, known from slice selective excitations [5], with every blade allows short echo times comparable to those obtained with conventional localization.