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Objectives: A feasibility proof‐of‐concept study was conducted to assess the effects of acute tibial nerve stimulation (TNS) on the central nervous system in healthy volunteers using functional magnetic resonance imaging (fMRI). Materials and Methods: Fourteen healthy volunteers were included in a prospective, single‐site study conducted on a clinical 3T MRI scanner. Four scans of functional MRI, each lasting 6 min, were acquired: two resting‐state fMRI scans (prior and following the TNS intervention) and in‐between two fMRI scans, both consisting of alternating rest periods and noninvasive acute transcutaneous TNS (TTNS). Whole brain seed‐based functional connectivity (FC) correlation analysis was performed comparing TTNS stimulation with rest periods. Cluster‐level familywise error (FWE) corrected p and a minimal cluster size of 200 voxels were used to explore FC patterns. Results: Increased FC is reported between inferior frontal gyrus, posterior cingulate gyrus, and middle temporal gyrus with the precuneus as central receiving node. In addition, decreased FC in the cerebellum, hippocampus, and parahippocampal areas was observed. Conclusions: Altered FC is reported in areas which have been described to be also involved in lower urinary tract control. Although conducted with healthy controls, the assumption that the underlying therapeutic effect of TNS involves the central nervous system is supported and has to be further examined in patients with incomplete spinal cord injury. [ABSTRACT FROM AUTHOR]

Diffusion kurtosis imaging (DKI) is applied to gain insights into the microstructural organization of brain tissues. However, the reproducibility of DKI outside brain white matter, particularly in combination with advanced estimation to remedy its noise sensitivity, remains poorly characterized. Therefore, in this study, we investigated the variability and reliability of DKI metrics while correcting implausible values with a fit method called mean kurtosis (MK)‐Curve. A total of 10 volunteers (four women; age: 41.4 ± 9.6 years) were included and underwent two MRI examinations of the brain. The images were acquired on a clinical 3‐T scanner and included a T1‐weighted image and a diffusion sequence with multiple diffusion weightings suitable for DKI. Region of interest analysis of common kurtosis and tensor metrics derived with the MK‐Curve DKI fit was performed, including intraclass correlation (ICC) and Bland–Altman (BA) plot statistics. A p value of less than 0.05 was considered statistically significant. The analyses showed good to excellent agreement of both kurtosis tensor‐ and diffusion tensor‐derived MK‐Curve–corrected metrics (ICC values: 0.77–0.98 and 0.87–0.98, respectively), with the exception of two DKI‐derived metrics (axial kurtosis in the cortex: ICC = 0.68, and radial kurtosis in deep gray matter: ICC = 0.544). Non‐MK‐Curve–corrected kurtosis tensor‐derived metrics ranged from 0.01 to 0.52 and diffusion tensor‐derived metrics from 0.06 to 0.66, indicating poor to moderate reliability. No structural bias was observed in the BA plots for any of the diffusion metrics. In conclusion, MK‐Curve–corrected DKI metrics of the human brain can be reliably acquired in white and gray matter at 3 T and DKI metrics have good to excellent agreement in a test–retest setting. [ABSTRACT FROM AUTHOR]

Purpose: The transverse relaxation times T2 of 17 metabolites in vivo at 3T is reported and region specific differences are addressed. Methods: An echo‐time series protocol was applied to one, two, or three volumes of interest with different fraction of white and gray matter including a total number of 106 healthy volunteers and acquiring a total number of 128 spectra. The data were fitted with the 2D fitting tool ProFit2, which included individual line shape modeling for all metabolites and allowed the T2 calculation of 28 moieties of 17 metabolites. Results: The T2 of 10 metabolites and their moieties have been reported for the first time. Region specific T2 differences in white and gray matter enriched tissue occur in 16 of 17 metabolites examined including single resonance lines and coupled spin systems. Conclusion: The relaxation time T2 is regions specific and has to be considered when applying tissue composition correction for internal water referencing. Magn Reson Med 80:452–461, 2018. © 2018 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

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.)

Purpose: The transverse relaxation times T 2 of 17 metabolites in vivo at 3T is reported and region specific differences are addressed., Methods: An echo-time series protocol was applied to one, two, or three volumes of interest with different fraction of white and gray matter including a total number of 106 healthy volunteers and acquiring a total number of 128 spectra. The data were fitted with the 2D fitting tool ProFit2, which included individual line shape modeling for all metabolites and allowed the T 2 calculation of 28 moieties of 17 metabolites., Results: The T 2 of 10 metabolites and their moieties have been reported for the first time. Region specific T 2 differences in white and gray matter enriched tissue occur in 16 of 17 metabolites examined including single resonance lines and coupled spin systems., Conclusion: The relaxation time T 2 is regions specific and has to be considered when applying tissue composition correction for internal water referencing. Magn Reson Med 80:452-461, 2018. © 2018 International Society for Magnetic Resonance in Medicine., (© 2018 International Society for Magnetic Resonance in Medicine.)