Brain γ‐aminobutyric acid (GABA) detection in vivo with the J‐editing 1H MRS technique: a comprehensive methodological evaluation of sensitivity enhancement, macromolecule contamination and test–retest reliability. (13th May 2016)

• Record Type: Journal Article
• Authors: Shungu, Dikoma C.; Mao, Xiangling; Gonzales, Robyn; Soones, Tacara N.; Dyke, Jonathan P.; van der Veen, Jan Willem; Kegeles, Lawrence S.
• Is Part Of: NMR in biomedicine. Volume 29:Number 7(2016:Jul.)
• Page Start: 932
• Page End: 942
• Publication Date: 2016-05-13
• Subjects: GABA -- Glutamate -- Glx -- 1H MRS -- J‐editing -- mobile macromolecules -- phased‐array coil -- test–retest reliability; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.3539
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : Abnormalities in brain γ‐aminobutyric acid (GABA) have been implicated in various neuropsychiatric and neurological disorders. However, in vivo GABA detection by 1 H MRS presents significant challenges arising from the low brain concentration, overlap by much stronger resonances and contamination by mobile macromolecule (MM) signals. This study addresses these impediments to reliable brain GABA detection with the J ‐editing difference technique on a 3‐T MR system in healthy human subjects by: (i) assessing the sensitivity gains attainable with an eight‐channel phased‐array head coil; (ii) determining the magnitude and anatomic variation of the contamination of GABA by MM; and (iii) estimating the test–retest reliability of the measurement of GABA with this method. Sensitivity gains and test–retest reliability were examined in the dorsolateral prefrontal cortex (DLPFC), whereas MM levels were compared across three cortical regions: DLPFC, the medial prefrontal cortex (MPFC) and the occipital cortex (OCC). A three‐fold higher GABA detection sensitivity was attained with the eight‐channel head coil compared with the standard single‐channel head coil in DLPFC. Despite significant anatomical variation in GABA + MM and MM across the three brain regions ( p < 0.05), the contribution of MM to GABA + MM was relatively stable across the three voxels, ranging from 41% to 49%, a non‐significant regional variation ( p = 0.58). The test–retest reliability of GABA measurement, expressed as either the ratio to voxel tissue water (W) or to total creatine, was found to be very high for both the single‐channel coil and the eight‐channel phased‐array coil. For the eight‐channel coil, for example, Pearson's correlation coefficient of test vs. retest for GABA/W was 0.98 ( R 2 = 0.96, p = 0.0007), the percentage coefficient of variation (CV) was 1.25% and the intraclass correlation coefficient (ICC) was 0.98. Similar reliability was also found for the co‐edited resonance of combined glutamate and glutamine (Glx) for both coils. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : Methodological evaluation of GABA detection by J‐editing 1H MRS shows (a) a factor of 3 enhancement in GABA detection SNR with an 8‐channel phased‐array head coil compared with a standard quadrature single‐channel coil; (b) contamination of GABA by mobile macromolecules (MM) in occipital, dorsolateral and medial prefrontal cortices of 41%‐49%, which is spatially invariant in normal brain; and (c) coefficient of variation (%CV) of 1.25% for test‐retest measurements of GABA with an inter‐scan interval of 60 min.