Andrey N. Pravdivtsev¹, Nicolas Kempf², Markus Plaumann³, Johannes Bernarding³, Klaus Scheffler², Jan-Bernd Hövener¹, and Kai Buckenmaier^2
1SBMI, MOIN CC, UKSH, Kiel University, Kiel, Germany, ²High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ³Institute for Biometrics and Medical Informatics, Otto-von-Guericke University, Magdeburg, Germany

We used signal amplification by reversible exchange of parahydrogen (SABRE)  at low (~1 mT) and ultra-low (~1 μT, ULF) magnetic fields. We proposed and used ULF correlation spectroscopy (COSY) method to analyze PHIP spin order in real-time. Coherences up to the third-order were observed experimentally. Furthermore, we analyzed SABRE in alternating magnetic fields (alt-SABRE). We measured the evolution of ¹H-¹⁵N zero-quantum coherences and have shown that they persist during field alternation and depend on the magnetic field strength. The resulting 15N-polarization in the alt-SABRE experiment was with magnetic was appoximately 30% higher. 

Christopher Michael Walker¹, Keith Michel¹, Collin J Harlan¹, Zhan Xu¹, Gary Martinez¹, Dawid Schellingerhout², Stephen Y. Lai³, and James A. Bankson^1
1Imaging Physics, MD Anderson Cancer Center, Houston, TX, United States, ²Neuroradiology Department, MD Anderson Cancer Center, Houston, TX, United States, ³Head & Neck Surgery, MD Anderson Cancer Center, Houston, TX, United States

Simulations were used to evaluate the effect of rapid vascular flow on spatial spectral pulses used for hyperpolarized MRI. Simulation results show that flow effects reduced the on-resonance excitation angle while increasing the off-resonance excitation in a velocity dependent manner. These excitation impacts will be particularly important when trying to estimate an arterial input function. Flow may also produce measurable lactate signal in flowing pyruvate, an effect that was observed in a hyperpolarized study of the thyroid.

Faraz Amzajerdian¹, Hooman Hamedani¹, Ryan Baron¹, Yi Xin¹, Tahmina Achekzai¹, Luis Loza¹, Mostafa Ismail¹, Ian Duncan¹, Stephen Kadlecek¹, Kai Ruppert¹, and Rahim Rizi^1
1University of Pennsylvania, Philadelphia, PA, United States

Quantifying the exchange of hyperpolarized xenon gas between the airways, lung parenchyma, and red blood cells may provide valuable insights into the progression of lung graft failure, enabling earlier diagnosis of chronic lung allograft dysfunction (CLAD). By combining Xenon polarization Transfer Contrast (XTC) imaging with a multi-breath model of fractional ventilation, gas exchange efficiency was assessed in four lung transplant recipients 3-12 months post-surgery in order to identify baseline metrics and trends.

Patrick Michael TomHon¹, Keilian MacCulloch¹, David Orestes Guarin², Erin Hardy², Austin Browning¹, Carlos Dedesma³, Matthew S Rosen², Yi-Fen Yen², and Thomas Theis^4
1Chemistry, North Carolina State University, Raleigh, NC, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Vizma Life Sciences, Chapel Hill, NC, United States, ⁴Chemistry, Physics, Biomedical Engineering, North Carolina State University, Raleigh, NC, United States

This work illustrates current advancements in SABRE hyperpolarized pyruvate toward in vivo imaging, demonstrating that significant levels of polarization achieved on pyruvate enable dynamic spectroscopy and imaging of downstream chemical products. Specifically in this study we show the monitoring of chemical conversion of pyruvate to pyruvate hydrate using a pH change and pyruvate to CO₂ by reaction with H₂O₂. While the current work only focuses on the study of the chemical conversion of hyperpolarized substrate in a phantom, these studies lay the groundwork for future in vivo injections that mirror these chemical conversion processes.

Liam S. P. Lawrence^1,2, Viktor Iakovenko³, Wendy Oakden¹, Rachel W. Chan¹, Greg J. Stanisz^1,2,4, and Angus Z. Lau^1,2
1Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Department of Medical Physics, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, ⁴Department of Neurosurgery and Paediatric Neurosurgery, Medical University, Lublin, Poland

1H MR spectroscopy (MRS) can detect metabolic changes in treated tumours that could indicate therapeutic response. MR response assessment might inform radiation dose plan adaptation on MRI linear accelerators (MR-Linacs). We report the first MRS experiments on a 1.5T MR-Linac. Dynamic spectra of yeast during fermentation were acquired with and without irradiation, to measure real-time changes in metabolism. Ethanol production was detectable. The Larmor frequency drifted by 33 Hz over 11 minutes during irradiation, degrading spectral quality. While no differences in ethanol production were detected between irradiation/control experiments, the phantom setup could be optimized to increase dose and improve repeatability.

Kai Ruppert¹, Tahmina S. Achekzai¹, Luis Loza¹, Faraz Amzajerdian¹, Yi Xin¹, Hooman Hamedani¹, Ryan J. Baron¹, Mostafa Ismail¹, Ian F. Duncan¹, Stephen Kadlecek¹, and Rahim R. Rizi^1
1University of Pennsylvania, Philadelphia, PA, United States

The thickness of the membrane separating the alveolar volume from the capillary blood is difficult measure with the chemical shift saturation recovery (CSSR) hyperpolarized xenon-129 MRI technique. In this work, we used a 1D gas exchange simulation to investigate the concept of measuring the gas-phase depolarization induced by the application of long RF pulses of variable power to extract information about the thickness of this membrane. Our simulations predict that measuring the red blood cell-induced gas-phase depolarization enables an estimation of membrane thickness even when the temporal lag between the rise in dissolved-phase signals cannot be accurately determined.

Marcia Sahaya Louis^1,2, Huijun Vicky Liao², Ajay Joshi¹, and Alexander Lin^2
1ECE, Boston University, Boston, MA, United States, ²Radiology, Brigham and Women's Hospital, Boston, MA, United States

Building normative databases for MR spectroscopy studies is much needed to further the use of MRS in large clinical studies.  The effect of differences in MRS parameters is not well documented and there are no established data harmonization methods for MRS data. Therefore, the goal of this study is to identify the effects of variations such as dwell time, coil type, and software version and describe a method for harmonizing data in healthy controls that will ameliorate those effects.

Yiling Liu¹, Jianfeng Bao², Hao Chen¹, Guiqin Liu³, Jingliang Chen², and Zhiyong Zhang^1
1School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ²The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China, ³Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China

Placements of lipid saturation bands not only demand a skillful MRSI scanning operation but also restrict the full brain MRSI coverage. Therefore, MRSI acquisition without lipid suppression while doing post-removal of lipid becomes clinically attractive and valuable. In this work, we propose to integrate hybrid CSI/EPSI acquisitions with L2 regularization for fast lipid removal of MRSI. The hybrid CSI/EPSI acquisitions rely on the same excitation and refocusing evolution with the modified CSI and EPSI sequences. Phantom and in-vivo brain studies demonstrate the effectiveness and low computational cost of the proposed method.

Alex Ensworth^1,2, Laura R. Barlow^3,4, Piotr Kozlowski^1,2,3,4, Erin L. MacMillan^3,4,5, and Cornelia Laule^1,2,3,6
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ²International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada, ³Radiology, University of British Columbia, Vancouver, BC, Canada, ⁴UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada, ⁵Philips Canada, Mississauga, ON, Canada, ⁶Pathology & Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada

The choice of repetition time (TR) in MR spectroscopy studies is widely debated. A shorter TR results in more clinically acceptable scan times, however due to T1 effects, the metabolite concentrations are reduced. We used semi-LASER MRS to compare the SNR and absolute metabolite concentrations for TR=2,5 and 8s. We demonstrate it is possible to achieve similar SNR and scan time using a TR of 5s with half the acquisitions compared to a TR of 2s, where the metabolite concentrations are 20% lower. Using a TR of 5s for any MRS study is feasible and recommended to minimize T1 effects.

Marilena M DeMayo^1,2,3,4,5, Alexander McGirr^2,3,4, Ben Selby^3,6, Frank MacMaster⁷, Chantel T Debert^3,6, and Ashley D Harris^1,3,5
1Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada, ²Department of Psychiatry, University of Calgary, Calgary, AB, Canada, ³Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, ⁴Mathison Centre for Mental Health Research and Education, University of Calgary, Calgary, AB, Canada, ⁵Department of Radiology, University of Calgary, Calgary, AB, Canada, ⁶Department of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada, ⁷Provincial Addiction and Mental Health (PAMH) Portfolio, University of Calgary, Calgary, AB, Canada

Small anatomically specific voxels in cerebral cortex require a large number of averages to quantify metabolites by magnetic resonance spectroscopy. It is unclear whether cortical regional variability in metabolite concentration requires small voxels, or whether a larger voxel which incorporates the region of interest can provide adequately representative measures with fewer averages. Concentrations of glutamate, glx, creatine, choline, myo­-inositol and N-acetyl-aspartate (NAA) were correlated within subjects between an overlapping small (15x15x15mm) and large (30x30x30mm) voxel. There was a significant correlation between creatine measures, while choline showed a positive trend. There was no correlation between glutamate, glx, NAA, and myo-inositol.

Tiffany Bell^1,2,3, Dana Goerzen⁴, Masoumeh Dehghani⁴, Jamie Near^4,5,6, and Ashley D Harris^1,2,3
1Department of Radiology, University of Calgary, Calgary, AB, Canada, ²Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, ³Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada, ⁴Centre d’Imagerie Cerebrale, Douglas Mental Health Institute, Montreal, QC, Canada, ⁵Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ⁶Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada

Measuring GABA in the human brain in vivo using magnetic resonance spectroscopy (MRS) is not trivial due to its low abundance in the brain and the overlap of signal from higher concentration metabolites. At 3T, an editing sequence is typically used to isolate the GABA signal. Data acquired at 7T has higher SNR and better spectral resolution, therefore editing is often not used to measure GABA at this field strength. Here we compare GABA levels acquired at 7T using STEAM to GABA levels acquired at 3T using GABA-edited MEGA-PRESS and find little agreement between the two measures.

Henri de Maissin^1,2, Vladislav Ivantaev¹, Christoph A. Müller^1,2, Obaid Mohiuddin¹, Jürgen Hennig³, Dominik von Elverfeldt³, Jan-Bernd Hövener⁴, Strefan Glöggler^5,6, and Andreas Benjamin Schmidt^1,2
1Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Center (DKFZ), Heidelberg, Germany, ³University Medical Center Freiburg, Freiburg, Germany, ⁴3Section Biomedical Imaging, Molecular Imaging North Competence Center (MOINCC), Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein and Kiel University, Kiel, Germany, ⁵Max Planck Institute for Biophysical Chemistry, Göttingen, Germany, ⁶Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany

Parahydrogen (pH₂) and Synthesis Amid the Magnet Bore Allow Dramatically Enhanced Nuclear Alignment (SAMBADENA) and have recently enabled hyperpolarization (HP) of ¹³C and subsequent in vivo administration of the produced contrast agent inside an MRI system. pH₂ Induced Polarization (PHIP) by Side-Arm Hydrogenation (PHIP-SAH) has extended the portfolio of PHIP agents to metabolically-active molecules such as acetate, lactate, and pyruvate, but typically requires hydrogenation in organic solvents like chloroform. Here we present our new, solvent-compatible SAMBADENA setup and preliminary results of the ¹³C HP in chloroform of the PHIP-SAH molecule cinnamyl-pyruvate – opening the pathway towards metabolic studies with SAMBADENA.