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Purpose: To evaluate the feasibility of motion correction for sodium ( 23 Na) MRI based on interleaved acquired 3D proton ( 1 H) navigator images., Methods: A 3D radial density-adapted sequence for interleaved 23 Na/ 1 H MRI was implemented on a 7 Tesla whole-body MRI system. The 1 H data obtained during the 23 Na acquisition were used to reconstruct 140 navigator image volumes with a nominal spatial resolution of (2.5 mm) 3 and a temporal resolution of 6 s. The motion information received from co-registration was then used to correct the 23 Na image dataset, which also had a nominal spatial resolution of (2.5 mm) 3 . The approach was evaluated on six healthy volunteers, whose motion during the scans had different intensities and characteristics., Results: Interleaved acquisition of two nuclei did not show any relevant influence on image quality (SNR of 13.0 for interleaved versus 13.2 for standard 23 Na MRI and 176.4 for interleaved versus 178.0 for standard 1 H MRI). The applied motion correction increased the consistency between two consecutive scans for all examined volunteers and improved the image quality for all kinds of motion. The SD of the differences ranged between 2.30% and 6.96% for the uncorrected and between 2.13% and 2.67% for the corrected images., Conclusion: The feasibility of interleaved acquired 1 H navigator images to be used for retrospective motion correction of 23 Na images was successfully demonstrated. The approach neither affected the 23 Na image quality nor elongated the scan time and can therefore be an important tool to improve the accuracy of quantitative 23 Na MRI., (© 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Purpose: To evaluate the repeatability of multinuclear interleaved 1 H/ 31 P NMR dynamic acquisitions in skeletal muscle and the impact of nuclear Overhauser enhancement (nOe) on the 31 P results at 3T in exercise-recovery and ischemia-hyperemia paradigms., Methods: A 1 H/ 31 P interleaved pulse sequence was used to measure every 2.5 s a perfusion-weighted image, a T 2 ∗ map, a 31 P spectrum and 32 1 H spectra sensitive to deoxymyoglobin. 21 subjects performed a plantar flexion exercise and after recovery underwent an 8-min lower leg ischemia. The procedure was repeated in visit 2 with 12 subjects. An additional exercise bout without 1 H excitation was appended to visit 1. Individual 1 H RF pulse nOe was measured at rest in every visit., Results: Repeatability scores (coefficient of variation, Bland-Altman analysis) were similar to those found in the literature using similar mono-nuclear acquisitions. |Pi]/[PCr], pH drop, creatine rephosphorylation rate (τ PCr ), maximum perfusion, time to peak perfusion, and blood flow post-exercise showed high reliability (intraclass correlation coefficient > 0.7), whereas hemodynamic results from reactive hyperemia showed higher repeatability. After accounting for nOe, which increased Pi and PCr signal-to-noise ratio by 30%, no differences in 31 P results were observed between interleaved and 31 P MRS-only acquisitions. τ PCr was unaffected by nOe., Conclusion: The method shows good repeatability for both paradigms while simultaneously providing multiple dynamic data sets on a clinical scanner. The nOe effects were accounted for on a per-subject and per-visit basis using a short 31 P reference scan. This multiparametric approach has a multitude of applications for the study of oxygen utilization and ATP turnover in the muscle., (© 2021 International Society for Magnetic Resonance in Medicine.)

Purpose: To measure the T1 and T2 relaxation times of water, metabolites, and macromolecules in the rat brain in vivo at 17.2T and achieve absolute quantification of the neurochemical profile. Relaxation times were compared with values from the literature found at lower magnetic fields., Methods: (1) H NMR spectra were measured using a LASER localization sequence. T1 - and T2 -weighted spectra were analyzed using LCModel with an original parameterization of the macromolecule baseline., Results: The T1 relaxation times of 20 metabolites and the T2 relaxation times of 16 singlets and J-coupled metabolites were measured. The mean T1 and T2 relaxation times for metabolites were 1721 ± 237 ms and 148 ± 53 ms, respectively. In addition, we measured the T1 and T2 relaxation times of 4 macromolecule resonance groups, their mean T1 and T2 relaxation times being 690 ± 100 ms and 37 ± 15 ms, respectively. Absolute quantification of 21 metabolites and 4 groups of macromolecule resonances was achieved with Cramer-Rao Lower Bounds below 5% for Cr, Gln, Glu, GPC, Ins, NAA, PCr, and Tau and below 25% for the remaining resonances., Conclusion: Comparison of our relaxation times to previously published values suggests a small increase of T1 values and a clear decrease of T2 values between 11.7 and 17.2T., (© 2015 Wiley Periodicals, Inc.)