The application of magnetic resonance fingerprinting to single voxel proton spectroscopy

Abstract

Magnetic resonance fingerprinting has been proposed as a method for undersampling k-space while simultaneously yielding multiparametric tissue maps. In the context of single voxel spectroscopy, fingerprinting can provide a unified framework for parameter estimation. We demonstrate the utility of such a magnetic resonance spectroscopic fingerprinting (MRSF) framework for simultaneously quantifying metabolite concentrations, T and T relaxation times and transmit inhomogeneity for major singlets of N-acetylaspartate, creatine and choline. This is achieved by varying T , T and the flip angle of the first pulse in a PRESS sequence between successive excitations (i.e. successive T values). The need for multiparametric schemes such as MRSF for accurate medical diagnostics is demonstrated with the aid of realistic in vivo simulations; these show that certain schemes lead to substantial increases to the area under receiver operating characteristics of metabolite concentrations, when viewed as classifiers of pathologies. Numerical simulations and phantom and in vivo experiments using several different schedules of variable length demonstrate superior precision and accuracy for metabolite concentrations and longitudinal relaxation, and similar performance for the quantification of transverse relaxation.

Potential clinical impact of multiparametric quantitative MR spectroscopy in neurological disorders: A review and analysis

“…Because T 1 and T 2 are known to change in disease, these additional data can be used to enhance clinical assessment and diagnosis. Similar interest has been shown recently in the field of MR spectroscopy (MRS), where knowledge of metabolites' relaxation constants and transmitter inhomogeneity serves 2 purposes: Metabolites' T 1 s and T 2 s probe microscopic changes in specific cellular environments. An example of this is n ‐acetyl‐aspartate (NAA), which is mostly found in neurons and is an established biomarker of neuronal health .…”

“…Existing multiparametric MRS acquisitions often entail varying sequence parameters (TE, TR, FA) to encode the relaxation parameters into the acquired signal . While optimal for relaxation measurements, these approaches can detract from the SNR per unit time and, consequently, impair quantification of metabolite concentrations.…”

Theoretical description of modern1H in Vivo magnetic resonance spectroscopic pulse sequences

“…171 A hybrid progressive saturation/inversion recovery technique has combined with MEGA-PRESS 172 ; inversion recovery has also been combined with the principles of magnetic resonance fingerprinting 173 (MRF) and applied to PRESS for simultaneous T 1 and T 2 mapping. 174 T 1 values range from as short as 397 AE 44 msec for GSH 121 to as long as 2264 AE 1206 msec in the NAA of HIV patients. 151 A comprehensive table listing the T 1 values of all metabolites measured with both progressive saturation or inversion recovery in the human brain is given in the Supplementary Materials.…”

“…Inversion recovery has been combined with PRESS, STEAM, MQF‐PRESS, MEGA‐PRESS, MEGA‐sLASER, and SPECIAL‐sLASER, an imaging sequence that obtains spatial localization through a spatial encoding and a slice‐selective excitation pulse . A hybrid progressive saturation/inversion recovery technique has combined with MEGA‐PRESS; inversion recovery has also been combined with the principles of magnetic resonance fingerprinting (MRF) and applied to PRESS for simultaneous T 1 and T 2 mapping …”

“…When correcting the data yielded by a particular experiment for T 2 effects, it is therefore best practice to use relaxation times measured with the same sequence and field strength, if available. Metabolite T 2 has been estimated using PRESS, STEAM, ISIS, MEGA‐PRESS, Carr‐Purcell‐Meiboom‐Gill PRESS, LASER, Carr‐Purcell‐LASER, sLASER, MEGA‐sLASER, JPRESS, MRSI, MRF‐PRESS, and a technique that uses RF‐driven steady states to avoid the requirement to sample multiple TEs, called MARzss …”