What is the optimal schedule for multiparametric MRS? A magnetic resonance fingerprinting perspective

Abstract

Clinical magnetic resonance spectroscopy (MRS) mainly concerns itself with the quantification of metabolite concentrations. Metabolite relaxation values, which reflect the microscopic state of specific cellular and sub-cellular environments, could potentially hold additional valuable information, but are rarely acquired within clinical scan times. By varying the flip angle, repetition time and echo time in a preset way (termed a schedule), and matching the resulting signals to a pre-generated dictionary an approach dubbed magnetic resonance fingerprintingit is possible to encode the spins' relaxation times into the acquired signal, simultaneously quantifying multiple tissue parameters for each metabolite. Herein, we optimized the schedule to minimize the averaged root mean square error (RMSE) across all estimated parameters: concentrations, longitudinal and transverse relaxation time, and transmitter inhomogeneity. The optimal schedules were validated in phantoms and, subsequently, in a cohort of healthy volunteers, in a 4.5 mL parietal white matter single voxel and an acquisition time under 5 minutes. The average intra-subject, inter-scan coefficients of variation (CVs) for metabolite concentrations, T 1 and T 2 relaxation times were found to be 3.4%, 4.6% and 4.7% in-vivo, respectively, averaged over all major singlets. Coupled metabolites were quantified using the short echo time schedule entries and spectral fitting, and reliable estimates of glutamate+glutamine, glutathione and myo-inositol were obtained.

FSL‐MRS: An end‐to‐end spectroscopy analysis package

“…Recent years have seen the emergence and rapid progress of new MRS technologies, including spectral editing, 1 MRS imaging, 2,3 time‐resolved functional MRS, 4 diffusion‐weighted MRS, 5 and MRS fingerprinting 6 . Magnetic resonance spectroscopy is, therefore, starting to have a range of techniques comparable to those of conventional proton MRI, but with the added benefit of being able to quantify specific chemical compounds.…”

FSL-MRS: An end-to-end spectroscopy analysis package

“…Recent years have seen the emergence and rapid progress of new magnetic resonance spectroscopy (MRS) technologies, including spectral editing (1), MRS imaging (2,3), time-resolved functional MRS (4), diffusion-weighted MRS (5), and MRS fingerprinting (6). MRS is therefore starting to have a range of techniques comparable to those of conventional proton MRI, but with the added benefit of being able to quantify specific chemical compounds.…”

Quantification of creatine kinase reaction rate in mouse hindlimb using phosphorus‐31 magnetic resonance spectroscopic fingerprinting

“…High‐resolution MRF methods for preclinical applications in small animals are also emerging 29–31 . Further, Kulpanovich and Tal have developed proton spectroscopic MRF (MRSF) methods for fast quantification of T 1 and T 2 relaxation times of several neural metabolites 32,33 . The feasibility of MRF for fast quantification of chemical exchange saturation transfer (CEST) has also been explored 34,35 …”

“…[29][30][31] Further, Kulpanovich and Tal have developed proton spectroscopic MRF (MRSF) methods for fast quantification of T 1 and T 2 relaxation times of several neural metabolites. 32,33 The feasibility of MRF for fast quantification of chemical exchange saturation transfer (CEST) has also been explored. 34,35 We recently explored the potential of using the MRF framework for rapid quantification of CK activity in vivo.…”