Stefan Wampl^1,2, Tito Körner^1,2, Sigrun Roat^1,2, Michael Wolzt³, Ewald Moser^1,2, Siegfried Trattnig^2,4, Martin Meyerspeer^1,2, and Albrecht Ingo Schmid^1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²MR Center of Excellence, Medical University of Vienna, Vienna, Austria, ³Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria, ⁴Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria

Cardiac phosphorus (³¹P) magnetic resonance spectroscopy (MRS) offers unique insights into the metabolism of the human heart. To further improve cardiac ³¹P MRS acquisitions, the implementation of a proton (¹H) magnetic resonance imaging (MRI) navigator into a ³¹P MRS pulse sequence using multinuclear interleaving is demonstrated. In this feasibility study we further apply a method to robustly detect the heart on low-resolution navigator images. Combined with multinuclear interleaving this facilitates time-efficient position updates of the ³¹P MRS voxel to prospectively correct for respiratory motion.

Fabian Niess^1,2, Albrecht Ingo Schmid^1,2, Siegfried Trattnig^2,3, Ewald Moser^1,2, and Martin Meyerspeer^1,2
1Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria, ²High-Field MR Centre, Medical University of Vienna, Wien, Austria, ³Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Wien, Austria

The purpose of this study is to show the effect of low-intensity exercise on localised ³¹P MR spectra and ¹H images of human muscle. It was determined which PCr depletion is sufficient for quantifying the PCr recovery time constant (τ_PCr), while incurring minimal pH drop in a predominantly glycolytic muscle. PCr depletion during exercise was measured, PCr recovery was fitted and pH was quantified with dynamic localised ³¹P MRS, while perfusion and BOLD ¹H images were simultaneously acquired in time-resolved measurements. Prolongation of τ_PCr with acidification was confirmed, while very short τ_PCr was found with neutral and slightly acidic pH.

Anouk Schrantee¹, Chloe Najac², Chris Jungerius², Aart J Nederveen¹, Vincent O Boer³, Wietske van der Zwaag⁴, Silvia Mangia⁵, and Itamar Ronen^2
1Department of Radiology and Nuclear Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands, ²C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ³Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, ⁴Spinoza Centre for Neuroimaging, Royal Netherlands Academy of Arts and Sciences, Amsterdam, Netherlands, ⁵Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Functional magnetic resonance spectroscopy can non-invasively measure changes in local concentrations of neurometabolites and has been used to demonstrate changes in lactate and glutamate levels in response to visual stimulation. However, whether the neurometabolite response scales with the level of neuronal stimulation like the BOLD response, has not been extensively investigated. We here show that lactate, but not glutamate levels, change dependent on visual contrast levels (baseline, 10%, 100% contrast). Although we also demonstrate a significant contrast dependence in the BOLD response, we do not find a significant association between the lactate response and the BOLD response.

Maike Hoefemann¹, André Döring¹, and Roland Kreis^1
1Departments of Radiology and Biomedical Research, University of Bern, Bern, Switzerland

A new sequence design was used to combine the CEST saturation method with traditional MRS. Using non-water suppressed metabolite-cycled spectroscopy offers the time-saving simultaneous recording of the traditional CEST z-spectrum and the metabolite spectrum under frequency selective saturation and allows the detection of exchange and magnetization transfer effects on metabolites and macromolecules. This technique might offer additional possibilities for quantifying the metabolite and macromolecular content or give further insight into the composition of the traditional CEST z-spectrum and is also relevant for judging the influence of water-suppression on absolute metabolite signals.

Masoumeh Dehghani^1,2, Richard Edden ³, and Jamie Near^1,2
1McGill University, Montreal, QC, Canada, ²Centre d'Imagerie Cérébrale, Montreal, QC, Canada, ³Johns Hopkins University, Baltimore, MD, United States

The spin echo, full Intensity acquired localized (SPECIAL) sequence consists of a localized spin-echo, preceded by an alternating ISIS pre-inversion for voxel localization. In this study we modified the SPECIAL sequence to simultaneously localize the signal at two different positions. The technique relies on a four-step inversion scheme involving two different inversion positions, followed by a Hadamard encoding reconstruction. Comparing the in vivo performance of dual-SPECIAL sequence to the conventional SPECIAL sequence demonstrated that the dual-Special sequence provides simultaneous metabolite profile from two different regions, reducing the acquisition time by a factor of two, and without any penalty in SNR.

Chengchuan Wu¹, Yasmin Blunck¹, and Leigh Johnston^1
1Biomedical Engineering, The University of Melbourne, Parkville, Australia

This work presents SELA, a ²³Na MRI sequence that can simultaneously acquire spin-density-weighted (SDW) and SNR-enhanced fluid-attenuated (FLAIR) images in one scan. The sequence was examined by numerical simulation and phantom experiment in a 7T preclinical scanner. Preliminary results support the design purpose to improve ²³Na MRI efficiency and ²³Na-FLAIR image quality.  

Wieland A Worthoff¹, Aliaksandra Shymanskaya², Karl-Josef Langen^1,3,4, and N. Jon Shah^1,2,4,5
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Jülich GmbH, Jülich, Germany, ²Institute of Neuroscience and Medicine - 11, Forschungszentrum Jülich GmbH, Jülich, Germany, ³Department of Nuclear Medicine, RWTH Aachen University, Aachen, Germany, ⁴Section JARA-Brain, Jülich-Aachen Research Alliance, Aachen, Germany, ⁵Department of Neurology, RWTH Aachen University, Aachen, Germany

A cohort of patients with untreated cerebral gliomas underwent consecutive [¹⁸F]-FET-PET and sodium MRI exams. It is shown that quantitative results from multiple quantum filtered sodium MRI using the enhanced SISTINA sequence offer access to the metabolic properties of tumours beyond what is observed by [¹⁸F]-FET-PET alone, thus presenting the potential to serve as an additional marker in tumour diagnostics.

Bernard Lanz¹, Radek Skupienski^2,3,4, Kim Q Do², and Lijing Xin^3
1LIFMET, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ²Center for Psychiatric Neuroscience, Department of Psychiatry, Lausanne University Hospital (CHUV), Prilly, Switzerland, ³Center for Biomedical Imaging (CIBM), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁴HES-SO, University of Applied Sciences of Western Switzerland, HEIA-FR, Institute of Chemical Technology, Fribourg, Switzerland

In this study, we applied interleaved localized ¹H-[¹³C]-MRS and direct ¹³C MRS with polarization transfer to characterize brain energy metabolism in the early development of a GCLM-KO mouse model with infusion of [2-¹³C]acetate. This strategy enabled to measure simultaneously the [2-¹³C]acetate input function, glutamate and glutamine C4 and C3 enrichment and pool size changes. Two-compartment metabolic modelling was then applied to characterize mitochondrial metabolism and glutamate/glutamine cycling and compare it to a control group.

Abigail R Molloy¹, Chloé Najac¹, Aliya Lakhani¹, Elavarasan Subramani¹, Georgios Batsios¹, Anne Marie Gillespie¹, Russell O Pieper^2,3, Pavithra Viswanath¹, and Sabrina M Ronen^1,3
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, United States, ³Brain Tumor Research Center, University of California, San Francisco, San Francisco, CA, United States

Mutant IDH1 (IDH1mut) drives glioma development, and targeted IDH1mut inhibitors show promising results in clinical trials. However, treatment is not associated with tumor shrinkage, and there is an urgent need for early imaging biomarkers of response. Our studies in IDH1mut-expressing glioma cells indicate that treatment with IDH1mut inhibitors leads to ¹H and ¹³C-MRS-detectable metabolic changes. Specifically, we show a decrease in 2-HG and increase in glutamate, as well as an increase in metabolic flux from glutamine to glutamate. Furthermore, hyperpolarized [1-¹³C] α-ketoglutarate can probe these alterations in metabolism. This identifies potential non-invasive biomarkers of response to IDH1mut inhibition in glioma.  

Jessie Mosso^1,2, Carole Poitry-Yamate¹, Dunja Simicic^1,2, Mario Lepore¹, Cristina Cudalbu¹, and Bernard Lanz^2
1Center for biomedical imaging (CIBM), EPFL, Lausanne, Switzerland, ²Laboratory for functional and metabolic imaging (LIFMET), EPFL, Lausanne, Switzerland

Hepatic encephalopathy (HE) is a severe complication of chronic liver disease which drastically affects patient lives. Its underlying mechanisms are still unknown and energy metabolism studies are of key interest. Here, we combined ¹⁸F-FDG PET and ¹H-MRS and found a 2-fold decrease in brain glucose uptake in a rat model of HE compared to SHAM rats, associated with a previously reported increase in brain glutamine and decrease in osmolytes. Although the difference in glucose uptake measured by PET results from a combination of brain and systemic effects, this finding provides a new perspective on HE pathophysiology.