Whole-Brain High-Resolution Metabolite Mapping with 3D Compressed-Sensing-SENSE-LowRank ¹H FID-MRSI

Abstract

There is a growing interest of the neuroscience community to map the distribution of brain metabolites in vivo. Magnetic resonance spectroscopy imaging (MRSI) is often limited by either a poor spatial resolution and/or a long acquisition time which severely limits its applications for clinical or research purposes. We developed a novel acquisition-reconstruction technique combining fast 1 H-FID-MRSI sequence accelerated by random k-space undersampling and a low-rank and totalgeneralized variation (TGV) constrained model. This framework was applied to the brain of four healthy volunteers. Following 20 min acquisition, reconstruction and quantification, the resulting metabolic maps with a 5 mm isotropic resolution reflected the detailed neurochemical composition of all brain regions and revealed part of the underlying brain anatomy. Contrasts and features from the 3D metabolite distributions were in agreement with the literature and consistent across the four subjects. The successful combination of the 3D 1 H-FID-MRSI with a constrained reconstruction enables the detailed mapping of metabolite concentrations at high-resolution in the whole brain and with an acquisition time that is compatible with clinical or research settings.

Proton metabolic mapping of the brain at 7 T using a two‐dimensional free induction decay–echo‐planar spectroscopic imaging readout with lipid suppression

“…The consequence of this is that removing lipid signals may also result in the loss of information related to other resonances. Some accelerated 3D FID‐MRSI studies have also reported related baseline distortions 45–47 . This was also evident in one of our example subjects (Figure 6C).…”

“…Some accelerated 3D FID-MRSI studies have also reported related baseline distortions. [45][46][47] This was also evident in one of our example subjects (Figure 6C). In addition, the L2-regularization method requires the F I G U R E 6 (A) T1-weighted image with the delineation of three regions of interest (ROIs) at V1.…”

“…As described by Klauser et al, 45 and also present in our images (Figure 5), these effects can lead to apparent metabolite gradients. To correct this gradient issue, advanced reconstruction methods such as low‐rank TGV, which take into consideration irregular receive profiles, can be implemented 45,47,70 . Addressing data variability, resulting from factors such as lipid contamination, acquisition‐dependent artifacts and reconstruction methods, is essential to promote wider clinical adoption of MRSI.…”

“…To correct this gradient issue, advanced reconstruction methods such as low-rank TGV, which take into consideration irregular receive profiles, can be implemented. 45,47,70 Addressing data variability, resulting from factors such as lipid contamination, acquisition-dependent artifacts and reconstruction methods, is essential to promote wider clinical adoption of MRSI. That being said, the EPSI readout has been used to investigate metabolic aberrations in various brain disorders such as brain tumors, [71][72][73][74] amyotrophic lateral sclerosis, 75 schizophrenia, 76 and dyslexia.…”

Randomized controlled trial of a mindfulness‐based intervention in adolescents from the general population: The Mindfulteen neuroimaging study protocol

“…All MRI data are acquired using the same 3T Magnetom TIM Trio scanner (Siemens, Germany) and 32‐channel array coil, at the Brain and Behaviour Laboratory, Faculty of Medicine, University of Geneva. Each MR‐imaging session comprises the following: a magnetization‐prepared rapid acquisition gradient (MPRAGE) sequence to assess grey and white matter volumes as well as cortical thickness, a diffusion spectrum imaging (DSI) sequence to investigate structural connectivity, a new in house spectroscopy imaging (MRSI) sequence to measure whole‐brain neurochemical properties, see on peer‐reviewed preprint (A. Klauser et al, 2020) and a functional Echo‐Planar Imaging sequence (EPI‐T2*) to record blood oxygen level signal, with a repetition time of 2100 ms, for both functional tasks and 8 min ‘resting state’ during which participants have for instructions to fix a white cross and let their mind wander, without falling asleep.…”