Short echo time 1H‐MRSI of the human brain at 3T with minimal chemical shift displacement errors using adiabatic refocusing pulses

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Abstract
The chemical shift displacement error (CSDE) is an often‐underestimated problem in slice selection for localized proton spectroscopy at higher fields. With the proposed semi‐localized by adiabatic selective refocusing (LASER) pulse sequence, this problem is dealt with by using RF pulses with bandwidths in the order of 5 kHz. A combination of conventional nonadiabatic slice‐selective excitation of proton spins, together with double slice‐selective refocusing of the spins by two pairs of adiabatic full‐passage (APF) pulses, produces a spin echo in a volume of interest (VOI) at an echo time down to 30 ms. An illustration of the CSDE of conventional point‐resolved spectroscopy (PRESS) and the semi‐LASER sequence is shown with a measurement of the brain of a volunteer at 3T. With one application of the technique to a patient with a glioblastoma multiforme (GBM), its clinical functionality is demonstrated. With sharp selection profiles and a small CSDE, voxels close to the edge of the VOI can also be used for evaluation. With the additional advantage of being relatively insensitive for B1 inhomogeneities, the semi‐LASER technique can be viewed as a superior substitute for conventional PRESS MR spectroscopic imaging (MRSI) at 3T and beyond. Magn Reson Med, 2007.