Methodological consensus on clinical proton MRS of the brain: Review and recommendations

Abstract

Proton MRS (1H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good‐quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi‐adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.

Theoretical description of modern1H in Vivo magnetic resonance spectroscopic pulse sequences

“…Recent reviews have covered editing, provided practical guides for high‐field spectroscopy, and recommendations for experimental and analysis details based on consensus . No recent review, however, has provided an in‐depth analysis and comparison of all commonly used MRS pulse sequences and their potential applications beyond standard concentration estimation.…”

In memoriam: Sarah J. Nelson, January 26, 1954–April 3, 2019

“…The cumulative impact of these efforts can only be partially summarized by the thousands of patient scans that were acquired using this software, the open-source spectral and image analysis software (SIVIC) 9 that she developed with Jason Crane, PhD (UCSF), and her 2 latest publications: a book chapter and consensus paper on proton spectroscopy. 10 Sarah's profound impact came not only through her many personal contributions to imaging science, but also through the careers of the mentees and protégés whom she helped to launch. Sarah was the epitome of selflessness.…”

“…Toward this goal she developed tools for automatically prescribing MRSI and processing the resulting spectra on the scanner, shared them across institutions, and trained technologists on their use. The cumulative impact of these efforts can only be partially summarized by the thousands of patient scans that were acquired using this software, the open‐source spectral and image analysis software (SIVIC) that she developed with Jason Crane, PhD (UCSF), and her 2 latest publications: a book chapter and consensus paper on proton spectroscopy …”

Adaptive Baseline Fitting for1H MR Spectroscopy Analysis

“…MRS scans are typically performed at short (30 ms) or long (144 ms) TE's, with short-TE scans being preferred due to reduced T2 relaxation and dephasing of multiplets resulting in improved metabolite detection sensitivity [6].…”

“…Clinical applications include the assessment of brain tumors, metabolic disorders and neonatal encephalopathy [1,2] where the concentration of certain metabolites may inform disease diagnosis or predict patient outcome. Further applications are present in the neuroscience and psychiatry domains, with particular interest in the direct detection of neurotransmitter levels such as GABA and glutamate -which have been shown to be abnormal in Schizophrenia [3] and modulate in response to tasks [4,5].MRS scans are typically performed at short (30 ms) or long (144 ms) TE's, with short-TE scans being preferred due to reduced T2 relaxation and dephasing of multiplets resulting in improved metabolite detection sensitivity [6].However, short-TE scans are typically more susceptible to artefacts originating from insufficient water and scalp lipid suppression, in addition, broad signals from macromolecules also become enhanced [7]. Residual water signals, lipid signals and macromolecules all have the potential to bias metabolite measurements due to spectral overlap and interference.…”