Jean-Philippe Ranjeva

In light of technical advancements supporting exploration of MR signals other than ¹H, MRI of other nuclei having magnetic properties such as sodium (²³Na), Oxygen (¹⁷O) or potassium (³⁹K) is developing in parallel with the increase of the magnetic fields of clinical MR scanners.These modalities receive attention as markers of ionic homeostasis and cell viability (²³Na, ³⁹K) or provide non-invasive way to determine cerebral metabolic rate of oxygen (CMR0₂) consumption using ¹⁷O MRI.During this course, we will present the practical issues to conduct MRI of these particular nuclei, hypotheses and proxy to derive the biophysical parameters from these images

Tanja Platt¹, Louise Ebersberger^2,3, Vanessa L Franke^1,4, Armin M Nagel^1,5,6, Reiner Umathum¹, Heinz-Peter Schlemmer², Peter Bachert^1,4, Mark E Ladd^1,3,4, Andreas Korzowski¹, Sebastian C Niesporek¹, and Daniel Paech^2
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, ²Radiology, German Cancer Research Center, Heidelberg, Germany, ³Faculty of Medicine, University of Heidelberg, Heidelberg, Germany, ⁴Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ⁵Institute of Radiology, University Hospital Erlangen, Erlangen, Germany, ⁶Institute of Medical Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany

Dynamic ¹⁷O-MRI enables direct quantification of the cerebral metabolic rate of oxygen (CMRO₂) consumption. We investigated hemispherical dependence of the method in three healthy volunteers as well as its potential for mapping neuronal activity associated with finger tapping in one healthy volunteer. Our findings were consistent with previous results, demonstrating higher CMRO₂ values in gray compared to white matter. Evaluation of left/right hemispheric CMRO₂ values without sensomotoric stimulation demonstrated hemispherical independence of the technique. The finger-tapping experiment demonstrated increased ¹⁷O-signal in the stimulated sensorimotor cortex and adjacent brain tissue, indicating that dynamic ¹⁷O-MRI may permit visualization of physiological neuronal activity.

Xi Chen¹, Elliot Kuan², Dost Ongur¹, Wei Chen³, and Fei Du^1
1McLean Hospital; Harvard Medical School, Belmont, MA, United States, ²McLean Hospital, Belmont, MA, United States, ³University of Minnesota, Minneapolis, MN, United States

Nicotinamide adenine dinucleotides play a crucial role in human health, but measuring the redox ratio (NAD+/NADH) in vivo is technically challenging and the confounding effects from UDPG remain unclear. In this study, for the first time we observed that the NAD+/NADH values decreased in 4T proton-decoupling spectra when the UDPG contribution was accounted for as well as confirming the opposite trend at 7T. Furthermore, we revealed different overlapping patterns at 4T and 7T which lead to this result. Finally, individual redox ratio measures with and without UDPG quantification are strongly correlated with one another at both 4T and 7T.

Yasmin Blunck^1,2, Daniel Staeb³, Rebecca K Glarin^2,4,5, Bradford A Moffat^2,4, Kieran O'Brien⁶, and Leigh A Johnston^1,2
1Department of Biomedical Engineering, University of Melbourne, Parkville, Australia, ²Melbourne Brain Centre Imaging Unit, University of Melbourne, Parkville, Australia, ³MR Research Collaborations, Siemens Healthcare Pty Ltd, Melbourne, Australia, ⁴Department of Medicine & Radiology, University of Melbourne, Parkville, Australia, ⁵Department of Radiology, Royal Melbourne Hospital, Parkville, Australia, ⁶MR Research Collaborations, Siemens Healthcare Pty Ltd, Brisbane, Australia

X-nuclei imaging like sodium MRI offers complementary information to ¹H-based imaging. However, its clinical translation is hampered by the significant increase in scan time required for the acquisition of an additional nuclei. Addressing this challenge, this work introduces Multiplexed Measurement of Multiple Nuclei (M³N) sequences and proposes MERINA-MP2RAGE, a multi-nuclei sequence, that embeds sodium MRI in a ¹H-MP2RAGE acquisition. The developed sequence was implemented on a 7T MRI and tested in phantom and human in vivo experiments. Merging ¹H-MP2RAGE and ²³Na-MERINA reduces the total scan time by 40% compared to sequential acquisitions while maintaining uncompromised image quality.

Henk De Feyter

Rui V Simoes¹, Javier Istúriz², Jonas L Olesen³, Sune N Jespersen³, and Noam Shemesh^1
1Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal, ²Neos Biotec, Pamplona, Spain, ³Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

As our understanding of cancer metabolism advances, novel methods are needed to dynamically assess its heterogeneity in preclinical models, with high temporal resolution. Here we show the feasibility of dynamic ²H-MRS in glioma-bearing mice to monitor glucose metabolism with <3s resolution. This was achieved with a new ²H/¹H RF coil design for the mouse brain and a novel application of Marchenko–Pastur denoising. We are now adapting this methodology to ²H-MRSI, with high spatial resolution.

Laurie J Rich¹, Puneet Bagga¹, Gabor Mizsei¹, Mitchell D Schnall¹, John A Detre², Mohammad Haris³, and Ravinder Reddy^1
1Radiology, University of Pennyslvania, Philadelphia, PA, United States, ²Neurology, University of Pennyslvania, Philadelphia, PA, United States, ³Research Branch, Qatar University, Doha, Qatar

Proton magnetic resonance spectroscopy (¹H MRS) is a powerful technique capable of detecting a range of endogenous metabolites, but with currently existing approaches does not enable tracking of metabolic fluxes and pathways. We report a new strategy which utilizes ¹H MRS in conjunction with administration of deuterium (²H) labeled glucose to track downstream labeling of neural metabolites. Since ²H is invisible on ¹H MRS, replacement of ¹H with ²H leads to an overall reduction in ¹H MRS signal for the corresponding metabolites. Therefore, this approach makes it possible to monitor neural metabolism using conventional and widely available ¹H MRS methodologies.