Jimin Ren^1,2, Craig R Malloy^1,2,3, and A Dean Sherry^1,2,4
1Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, ²Department of Radiology, UT Southwestern Medical Center, Dallas, TX, United States, ³VA North Texas Health Care System, Dallas, TX, United States, ⁴Department of Chemistry, University of Texas at Dallas, Richardson, TX, United States

A variety of nucleotide sugars (NS) are required for glycosylation of proteins and lipids to enhance and diversify cellular functions. The current 7T ³¹P MRS study, for the first time, reports the detection of four different NS species in human brain in vivo. They are tentatively assigned to UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, and UDP-N-acetylgalactosamine, collectively denoted as UDP(G). These UDP(G) species are responsible for the observation of a “quartet-like” signal at -9.8 ppm, which cannot be explained by the presence of only a single UDP(G) species such as UDP-glucose (as expected to be a simple doublet).

Loreen Ruhm¹, Johanna Dorst¹, Nikolai Avdievich¹, and Anke Henning^1,2
1Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ²UT Southwestern Medical Center, Dallas, TX, United States

³¹P Magnetic Resonance Spectroscopic Imaging (MRSI) is a non-invasive method that can reveal information about the energy and phospholipid metabolism. In this work, we investigate the differences in signal amplitudes of different ³¹P metabolites between grey and white matter tissue in the human brain. We acquired highly resolved ³¹P MRSI data at an ultrahigh field strength B₀ of 9.4 T from the brain of six healthy volunteers. For the quantification of the ³¹P MRSI data, different correction were applied to the signal amplitudes.

William T Clarke¹, Lukas Hingerl², Wolfgang Bogner², Ladislav Valkovic^3,4, and Christopher T Rodgers^3,5
1Wellcome Centre for Integrative Neuroimaging, NDCN, University of Oxford, Oxford, United Kingdom, ²High-field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ³Oxford Centre for Clinical Magnetic Resonance Research, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom, ⁴Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia, ⁵Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom

A density-weighted concentric ring trajectory MRSI sequence is implemented for cardiac ³¹P-MRS at 7T. The sequence is characterised in phantoms and in five healthy participants. Quantitative comparisons are made against a previously implemented acquisition weighted CSI sequence with matched acquisition time and voxel size. The proposed sequence (CONCEPT) was found to robustly measure 3D localised PCr/ATP ratios of the human myocardium 2.59 times faster or with 1.73 times smaller nominal volume than standard acquisition weighted CSI.

Sam Keaveney¹, Ross Maxwell¹, Maelene Lohézic², Rolf Schulte³, Ralph Noeske⁴, and Andrew Blamire^1
1Newcastle Magnetic Resonance Centre, Newcastle University, Newcastle upon Tyne, United Kingdom, ²GE Healthcare, Manchester, United Kingdom, ³GE Healthcare, Munich, Germany, ⁴GE Healthcare, Berlin, Germany

Mitochondrial function in the brain can be measured with magnetisation transfer ³¹P-MRS. The conventional approach to magnetisation transfer incurs lengthy acquisition times, limiting the available spatial information. An accelerated approach, based on kinetic modelling, allows the technique to be extended to a multi-voxel implementation. Both approaches were applied in a group of healthy subjects to measure the rate of the creatine kinase reaction. There was good agreement between the reaction rates measured with the two methods in equivalently positioned voxels, validating the use of the accelerated approach to provide greater spatial resolution in future patient studies.

Celine Baligand^1,2, Jean-Baptiste Perot^1,2, Didier Thenadey^1,2, Julien Flament^1,2, Marc Dhenain^1,2, and Julien Valette^1,2
1Molecular Imaging Research Center (MIRCen), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Fontenay-aux-Roses, France, ²Neurodegenerative Diseases Laboratory (UMR 9199), Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, Fontenay-aux-Roses, France

The cerebral metabolic rate of oxygen consumption (CMRO₂) is an important metric of brain metabolism. It is of particular interest in preclinical studies of Alzheimer’s disease, where amyloidosis has been associated with impaired mitochondrial function. CMRO₂ can be measured by direct ¹⁷O-MRI of H₂¹⁷O signal changes during inhalation of ¹⁷O-labeled oxygen gas. In this study, we used 3D zero echo time ¹⁷O-(ZTE-)MRI at 11.7T to measure CMRO₂ in the APP/PS1_dE9 mouse model of amyloidosis and show that it is significantly lower than in control mice.

Hao Song¹, Yanis Taege¹, Johannes Fischer¹, Ali Caglar Özen^1,2, and Michael Bock^1,2
1Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, ²German Consortium for Translational Cancer Research (DKTK) Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany

In this work, regional quantification of the cerebral metabolic rate of oxygen consumption (CMRO₂) was performed using dynamic ¹⁷O-MRI with inhalation of isotope-enriched ¹⁷O₂. First, global mean CMRO₂ values were determined in cortical grey matter and white matter. Then, local CMRO₂ was investigated in frontal, parietal and occipital areas, respectively. The results were in good agreement with previously reported PET values especially for the cortical grey matter. For regional analysis, the CMRO₂ values show good consistency across the white matter and in both frontal and parietal cortical grey matter.

Muhammad H. Khan¹, John J. Walsh¹, Sandeep K. Mishra², Daniel Coman², and Fahmeed Hyder^1,2
1Biomedical Engineering, Yale University, New Haven, CT, United States, ²Radiology & Biomedical Imaging, Yale University, New Haven, CT, United States

The transmembrane sodium gradient (difference between extracellular and intracellular concentrations) is necessary for the proper functioning of many bodily mechanisms, including action potential propagation and osmoregulation. While unbound sodium-23 (²³Na) is fully detectable by NMR, it is not possible to discriminate between compartments because all ²³Na signals resonate at the same frequency. Our objective is to induce ²³Na chemical shift differences across cellular compartments with exogenous contrast agents that occupy the interstitial space. We applied this approach successfully in vivo to determine the variation of the transmembrane gradient in glioblastoma.

Ahmad Alhulail^1,2, Pingyu Xia¹, Xin Shen³, Miranda Nichols¹, Srijyotsna Volety¹, Nicholas Farley¹, Armin M Nagel⁴, Ulrike Dydak^1,5, and Uzay E Emir^1,3
1School of Health Sciences, Purdue University, West Lafayette, IN, United States, ²Department of Radiology and Medical Imaging, Prince Sattam bin Abdulaziz University, Al Kharj, Saudi Arabia, ³Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States, ⁴Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, ⁵Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, United States

Sodium signal decays quickly and bi-exponentially, which make T₂ relaxation fitting and absolute quantification challenging. Estimating T₂ with enough data points using multiple echoes requires an impractical acquisition time. Alternatively, we propose a fast sodium 2D-FID-MRSI sequence to collect the decaying signal with a high sampling frequency (625 Hz) starting at 0.55 ms within only 4 minutes at 3T. We demonstrate an absolute concentration map and separate maps of fast (mean: 0.4 ±0.4 ms) and slow (mean: 19.6 ±5.7 ms) T₂* components from human calf muscles, showing that rapid data collection for T₂* correction is feasible with this ²³Na-MRSI method.

Kalen J. Petersen¹, Maria Garza¹, Cassandra Reynolds², Deepak Gupta², Manus J. Donahue^1,3,4, and Rachelle Crescenzi^1
1Radiology, Vanderbilt University Medical Center, Nashville, TN, United States, ²Cardiology, Vanderbilt University Medical Center, Nashville, TN, United States, ³Neurology, Vanderbilt University Medical Center, Nashville, TN, United States, ⁴Psychiatry, Vanderbilt University Medical Center, Nashville, TN, United States

Salt sensitive blood pressure (SSBP) is a cardiovascular disease risk factor, yet clinically-feasible biomarkers of SSBP have not been developed. We tested the hypothesis that peripheral tissue sodium content (TSC), measured with ²³Na-MRI, is higher in persons with vs. without SSBP (n=39 total; age=29.4±7.4 years; sex=21/18 F/M). SSBP was confirmed by independent measurement of BP increase >5 mmHg after high-salt diet compared to low-salt diet. SSBP participants (n=13) had elevated leg skin TSC (p=0.04), and TSC was inversely correlated with leg fat-fraction (ρ=-0.57; p<0.001). Findings suggest that multi-nuclear ²³Na/¹H-MRI could provide a radiological screening tool for SSBP.

Johanna Lott^1,2, Armin M. Nagel^1,3,4, Sebastian C. Niesporek¹, Thoralf Niendorf^5,6, Peter Bachert^1,2, Mark E. Ladd^1,2,7, and Tanja Platt^1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ³Institute of Radiology, University Hospital Erlangen, Erlangen, Germany, ⁴Institute of Medical Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, ⁵Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ⁶MRI. TOOLS GmbH, Berlin, Germany, ⁷Faculty of Medicine, University of Heidelberg, Heidelberg, Germany

Sodium (²³Na) ion distribution plays a fundamental role in biological processes, in particular in myocardial function. ²³Na MRI provides noninvasive information about the total tissue sodium concentration. However, short relaxation times, low signal-to-noise ratio, breathing and heart motion render quantitative cardiac ²³Na MRI challenging and result in long acquisition times. We present a method to compensate for respiratory motion in ²³Na MRI by adding a linear phase in k-space with the goal to determine myocardial tissue sodium concentration. This enables a reduced measurement time for quantitative cardiac ²³Na MRI compared to retrospective sorting into one respiratory state.