Search

Background: The optimization of magnetic resonance spectroscopy (MRS) sequences allows improved diagnosis and prognosis of neurological and psychological disorders. Thus, to assess the test-retest and intersequence reliability of such MRS sequences in quantifying metabolite concentrations is of clinical relevance., Purpose: To evaluate the test-retest and intersequence reliability of three MRS sequences to estimate GABA and Glx = Glutamine+Glutamate concentrations in the human brain., Study Type: Prospective., Subjects: Eighteen healthy participants were scanned twice (range: 1 day to 1 week between the two sessions) with identical protocols., Field Strength/sequence: 3T using a 32-channel SENSE head coil in the PCC region; PRESS, JPRESS, and MEGA-PRESS sequences., Assessment: Metabolite concentrations were estimated using LCModel (for PRESS and MEGA-PRESS) and ProFit2 (for JPRESS)., Statistical Tests: The test-retest reliability was evaluated by Wilcoxon signed-rank tests, Pearson's r correlation coefficients, intraclass-correlation coefficients (ICC), coefficients of variation (CV), and by Bland-Altman (BA) plots. The intersequence reliability was assessed with Wilcoxon signed-rank tests, Pearson's r correlation coefficients, and BA plots., Results: For GABA, only the MEGA-PRESS sequence showed a moderate test-retest correlation (r = 0.54, ICC = 0.5, CV = 8.8%) and the BA plots indicated good agreement (P > 0.05) for all sequences. JPRESS provided less precise results and PRESS was insensitive to GABA. For Glx, the r and ICC values for PRESS (r = 0.87, ICC = 0.9, CV = 2.9%) and MEGA-PRESS (r = 0.70, ICC = 0.7, CV = 5.3%) reflect higher correlations, compared with JPRESS (r = 0.39, ICC = 0.4, CV = 20.1%)., Data Conclusion: MEGA-PRESS and JPRESS are suitable for the reliable detection of GABA, the first being more precise. The three sequences included in the study can measure Glx concentrations., Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1181-1191., (© 2019 International Society for Magnetic Resonance in Medicine.)

Background: Multiple sedation regimes may be used to facilitate pediatric MRI scans. These regimes might affect cerebral blood flow and hemodynamics to varying degrees, particularly in children who may be vulnerable to anesthetic side effects., Purpose: To compare the effects of propofol monosedation solely (Pm group) vs. a combination of propofol and ketamine (KP group) on brain hemodynamics and perfusion., Study Type: Prospective double-blind randomized trial., Field Strength/sequences: 1.5T and 3T. 2D-Cine phase contrast (2D-Cine PC) and pseudocontinuous arterial spin labeling (ASL)., Population: Children aged from 3 months to 10 years referred for MRI with deep sedation were randomized into either the KP or the Pm group. Perfusion images were acquired with ASL followed by single-slice 2D-Cine PC acquired between the cervical vertebra C2 and C3., Assessment: Average whole-brain perfusion (WBP ml.min -1 .100 ml -1 ) was extracted from the ASL perfusion maps and total cerebrovascular blood flow (CVF) was quantified by bilaterally summing the flow in the vertebral and the internal carotid arteries. The CVF values were converted to units of ml.min -1 .100 g -1 to calculate the tissue CVF 100g (ml.min -1 .100 g -1 ). Images were assessed by a neuroradiologist and data from n = 81 (ASL) and n = 55 (PC) cases with no apparent pathology were entered into the analysis., Statistical Tests: Multivariate analysis of covariance was performed to compare drug sedation effects on WBP, CVF, and CVF 100g ., Results: No significant difference in arterial flow was observed (P = 0.57), but the KP group showed significantly higher WBP than the Pm group, covarying for scanner and age (P = 0.003). A correlation analysis showed a significant positive correlation between mean WBP (ml.min -1 .100 g -1 ) and mean CVF 100g ., Data Conclusion: The KP group showed higher perfusion but no significant difference in vascular flow compared with the Pm group. WBP and CVF 100g correlated significantly, but ASL appeared to have more susceptibility to perfusion differences arising from the different sedation regimes., Level of Evidence: 1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2019;50:1433-1440., (© 2019 International Society for Magnetic Resonance in Medicine.)

Purpose: Idiopathic generalized epilepsies (IGE) comprise a group of clinical syndromes associated with spike wave discharges, putatively linked to alterations in neurotransmission. The purpose of this study was to investigate whether patients with IGE have altered glutamine and γ-aminobutyric acid (GABA) levels indicative of altered excitatory and inhibitory neurotransmission in frontal regions., Materials and Methods: Single-voxel MEGA-edited PRESS magnetic resonance imaging (MRI) spectra were acquired from a 30-mL voxel in the dorsolateral prefrontal cortex in 13 patients with IGE (8 female) and 16 controls (9 female) at 3T. Metabolite concentrations were derived using LCModel. Differences between groups were investigated using an unpaired t-test., Results: Patients with IGE were found to have significantly higher glutamine than controls (P = 0.02). GABA levels were also elevated in patients with IGE (P = 0.03)., Conclusion: Patients with IGE have increased frontal glutamine and GABA compared with controls. Since glutamine has been suggested to act as a surrogate for metabolically active glutamate, it may represent a marker for excitatory neurotransmission., (© 2014 Wiley Periodicals, Inc.)

Purpose: To evaluate the reproducibility of γ-amino-butyric acid (GABA) and glutamate concentrations derived using three different spectral fitting methods, and to investigate gender-related differences in neurotransmitter levels., Materials and Methods: Single voxel MEGA-edited PRESS MR spectra were acquired from a 30-mL voxel in the dorso-lateral prefrontal cortex in 14 adult volunteers (7 female) at 3 Tesla (3T). For each participant, four consecutive resting spectra were acquired within the same scanning session. Metabolite concentrations were derived using LCModel, jMRUI, and locally written peak fitting software. The within-session reproducibility for each analysis method was calculated as the average coefficient of variation (CV) of the GABA and Glx (glutamate+glutamine) concentrations. Gender differences in GABA and Glx were evaluated using a two-tailed unpaired t-test., Results: LCModel provided the best reproducibility for both GABA (CV 7%) and Glx (CV 6%). GABA, Glx, and glutamate concentrations were significantly higher in the male participants, (P = 0.02, P = 0.001, and P < 0.001, respectively)., Conclusion: GABA and glutamate can be quantified in vivo with high reproducibility (CV 6-7%) using frequency-domain spectral fitting methods like LCModel. However, the GABA and glutamate concentrations vary significantly between men and women, emphasizing the importance of gender-matching for studies investigating differences in neurotransmitter concentrations between mixed-cohort groups., (Copyright © 2011 Wiley-Liss, Inc.)