In this acute intervention study, we investigated the potential benefit of ketone supplementation in humans by studying cardiac phosphocreatine to adenosine-triphosphate ratios (PCr/ATP) and... Show moreIn this acute intervention study, we investigated the potential benefit of ketone supplementation in humans by studying cardiac phosphocreatine to adenosine-triphosphate ratios (PCr/ATP) and skeletal muscle PCr recovery using phosphorus magnetic resonance spectroscopy (P-31-MRS) before and after ingestion of a ketone ester drink. We recruited 28 healthy individuals: 12 aged 23-70 years for cardiac P-31-MRS, and 16 aged 60-75 years for skeletal muscle P-31-MRS. Baseline and post-intervention resting cardiac and dynamic skeletal muscle P-31-MRS scans were performed in one visit, where 25 g of the ketone monoester, deltaG(R), was administered after the baseline scan. Administration was timed so that post-intervention P-31-MRS would take place 30 min after deltaG(R) ingestion. The deltaG(R) ketone drink was well-tolerated by all participants. In participants who provided blood samples, post-intervention blood glucose, lactate and non-esterified fatty acid concentrations decreased significantly (-28.8%, p MUCH LESS-THAN 0.001; -28.2%, p = 0.02; and -49.1%, p MUCH LESS-THAN 0.001, respectively), while levels of the ketone body D-beta-hydroxybutyrate significantly increased from mean (standard deviation) 0.7 (0.3) to 4.0 (1.1) mmol/L after 30 min (p MUCH LESS-THAN 0.001). There were no significant changes in cardiac PCr/ATP or skeletal muscle metabolic parameters between baseline and post-intervention. Acute ketone supplementation caused mild ketosis in blood, with drops in glucose, lactate, and free fatty acids; however, such changes were not associated with changes in P-31-MRS measures in the heart or in skeletal muscle. Future work may focus on the effect of longer-term ketone supplementation on tissue energetics in groups with compromised mitochondrial function. Show less
Schmitz Abecassis, B.; Vinogradov, E.; Wijnen, J.P.; Harten, T. van; Wiegers, E.C.; Hoogduin, H.; ... ; Ercan, E. 2021
Purpose Current challenges of in vivo CEST imaging include overlapping signals from different pools. The overlap arises from closely resonating pools and/or the broad magnetization transfer... Show morePurpose Current challenges of in vivo CEST imaging include overlapping signals from different pools. The overlap arises from closely resonating pools and/or the broad magnetization transfer contrast (MTC) from macromolecules. This study aimed to evaluate the feasibility of variable delay multipulse (VDMP) CEST to separately assess solute pools with different chemical exchange rates in the human brain in vivo, while mitigating the MTC. Methods VDMP saturation buildup curves were simulated for amines, amides, and relayed nuclear Overhauser effect. VDMP data were acquired from glutamate and bovine serum albumin phantoms, and from six healthy volunteers at 7T. For the in vivo data, MTC removal was performed via a three-pool Lorentzian fitting. Different B-1 amplitudes and mixing times were used to evaluate CEST pools with different exchange rates. Results The results show the importance of removing MTC when applying VDMP in vivo and the influence of B-1 for distinguishing different pools. Finally, the optimal B-1 and mixing times to effectively saturate slow- and fast-exchanging components are also reported. Slow-exchanging amides and rNOE components could be distinguished when using B-1 = 1 mu T and t(mix) = 10 ms and 40 ms, respectively. Fast-exchanging components reached the highest saturation when using a B-1 = 2.8 mu T and t(mix) = 0 ms. Conclusion VDMP is a powerful CEST-editing tool, exploiting chemical exchange-rate differences. After MTC removal, it allows separate assessment of slow- and fast-exchanging solute pools in in vivo human brain. Show less
High-permittivity dielectric pads, i.e., thin, flexible slabs, usually consisting of mixed ceramic powders and liquids, have been previously shown to increase the magnetic field at high and ultra... Show moreHigh-permittivity dielectric pads, i.e., thin, flexible slabs, usually consisting of mixed ceramic powders and liquids, have been previously shown to increase the magnetic field at high and ultra high-fields in regions of low efficiency of transmit coils, thus improving the homogeneity of images. However, their material parameters can change with time, and some materials they contain are bio incompatible. This article presents an alternative approach replacing ceramic mixtures with a low-cost and stable artificial dielectric slab. The latter comprises a stack of capacitive grids realized using multiple printed-circuit boards. Results in this article show that the proposed artificial dielectric structure can obtain the same increase in the local transmit radiofrequency magnetic field distribution in a head phantom at 7 T as the conventional dielectric pad. (C) 2020 The Authors. Published by Elsevier Inc. Show less
Background: The combination of EEG and ultra-high-field (7T and above) fMRI holds the promise to relate electrophysiology and hemodynamics with greater signal to noise level and at higher spatial... Show moreBackground: The combination of EEG and ultra-high-field (7T and above) fMRI holds the promise to relate electrophysiology and hemodynamics with greater signal to noise level and at higher spatial resolutions than conventional field strengths. Technical and safety restrictions have so far resulted in compromises in terms of MRI coil selection, resulting in reduced, signal quality, spatial coverage and resolution in EEG-fMRI studies at 7 T.New method: We adapted a 64-channel MRI-compatible EEG cap so that it could be used with a closed 32-channel MRI head coil thus avoiding several of these compromises. We compare functional and anatomical as well as the EEG quality recorded with this adapted setup with those recorded with a setup that uses an open-ended 8-channel head-coil.Results: Our set-up with the adapted EEG cap inside the closed 32 channel coil resulted in the recording of good quality EEG and (f)MRI data. Both functional and anatomical MRI images show no major effects of the adapted EEG cap on MR signal quality. We demonstrate the ability to compute ERPs and changes in alpha and gamma oscillations from the recorded EEG data.Comparison with existing methods: Compared to MRI recordings with an 8-channel open-ended head-coil, the loss in signal quality of the MRI images related to the adapted EEG cap is considerably reduced.Conclusions: The adaptation of the EEG cap permits the simultaneous recording of good quality whole brain (f) MRI data using a 32 channel receiver coil, while maintaining the quality of the EEG data. Show less
Bank, B.L. van de; Emir, U.E.; Boer, V.O.; Asten, J.J.A. van; Maas, M.C.; Wijnen, J.P.; ... ; Scheenen, T.W.J. 2015
