Wolfgang Gottwald¹, Luca Nagel¹, Geoffrey J. Topping¹, and Franz Schilling^1
1Department of Nuclear Medicine, TUM School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany

A multi-voxel point resolved spectroscopy (MV-PRESS) sequence was developed for measuring hyperpolarized ¹³C-labelled compounds, on a 7T preclinical small animal scanner. MV-PRESS allows to excite selected imaging voxels within a 3D volume with high sensitivity (i.e. 90° excitation angle). This method was compared to both single-voxel PRESS of a thermal ¹H phantom and CSI with a hyperpolarized [1-¹³C]pyruvate phantom. MV-PRESS was then used to detect both pyruvate and lactate in healthy mouse kidneys after hyperpolarized [1-¹³C]pyruvate injection, using 2x2x2 mm³ voxels for a total of 4 voxels.

Nicholas Bryden¹, Michele Kelley¹, Christian T McHugh¹, and Rosa T Branca^1
1University of North Carolina Chapel Hill, Chapel Hill, NC, United States

We provide longitudinal relaxation measurements of hyperpolarized (HP) ¹²⁹Xe gas dissolved in a variety of solvents at both low and high magnetic field strengths. The method of measuring T₁ presented here is less sensitive than more commonly used methods to RF flip angle miscalibration, which has caused the significant variation in dissolved-phase ¹²⁹Xe T₁ values reported in the past. A field dependent study of gas depolarization by hollow membrane fibers commonly used to dissolve xenon in blood or other solvents is also included, which provides insight to experimental limitations on their use in both field regimes.

Cornelius von Morze¹, Tyler Blazey¹, Richard Baeza², Ruslan Garipov², Timothy Whitehead¹, Galen D Reed³, Joel R Garbow¹, and Kooresh I Shoghi^1
1Washington University, St Louis, MO, United States, ²MR Solutions, Guildford, United Kingdom, ³GE Healthcare, Dallas, TX, United States

Hyperpolarized (HP) ¹³C MRI requires advanced pulse sequences to capture the dynamic, localized metabolic information. We developed an echo planar spectroscopic imaging (EPSI) pulse sequence incorporating multi-band spectral-spatial radiofrequency (SSRF) pulses for rapid and efficient HP ¹³C MRI on a new cryogen-free simultaneous PET/MR molecular imaging platform with compact footprint. Excitation profiles were measured in phantoms, and the SSRF-EPSI sequence was tested in rats using two HP ¹³C probes. We also obtained simultaneous ¹⁸F-FDG-PET data for comparison. In conclusion, advanced ¹³C SSRF imaging approaches are feasible on the new PET/MR platform, facilitating direct comparison with PET.

Francesca Reineri¹, Oksana Bondar¹, Carla Carrera², Eleonora Cavallari¹, Erika Cerutti¹, Ginevra Di Matteo¹, and Silvio Aime^1
1Molecular Biotechnology, University of Torino, Torino, Italy, ²Institute of Biostructure and Bioimaging, Nation Research Council, Torino, Italy

ParaHydrogen Induced Polarization is a hyperpolarization method much less technically demanding and affordable than d-DNP. The Side Arm Hydrogenation method allowed to obtain hyperpolarized [1-13C]pyruvate that can be used for metabolic studies, but concerns about the safety and bio-compatibility of the final aqueous solution of the HP products may be present, due to organic solvents and metal complex. In this work, a method to remove all the traces of toxic solvents and metal complex from the final product will be presented, together with the ¹³C-MR images obtained using the metabolite thus hyperpolarized.

Yohn C.G. Taylor¹, Frederick J. Wilson², and Geoff J.M. Parker^1,3
1Centre for Medical Image Computing, Quantitative Imaging Group, Department of Medical Physics & Biomedical Engineering, University College London, London, United Kingdom, ²GlaxoSmithKline R&D, Stevenage, United Kingdom, ³Bioxydyn Limited, Manchester, United Kingdom

Univariate sensitivity analysis was used to determine parameter importance within the model of gas exchange (MOXE) for lung hyperpolarised ¹²⁹Xe MRS/MRI. Sensitivity of the model to parameter variation across a range of saturation recovery delay times within the chemical shift saturation recovery (CSSR) technique was assessed. Simulated parameter values spanned those in healthy and patient groups. MOXE is found to be most sensitive to changes in surface-area-to-volume ratio and in septal wall thickness. MOXE is negligibly sensitive to alveoli-capillary barrier thickness. CSSR measurements taken within delay periods between 0 - 200 ms provide optimum parameter sensitivity.

Michele Kelley¹ and Rosa Tamara Branca^1
1Department of Physics and Astronomy, University of North Carolina - Chapel Hill, Chapel Hill, NC, United States

To increase the ¹²⁹Xe polarization for emerging biomedical applications, the Rb polarization on which the ¹²⁹Xe directly depends must be first optimized. Radiation trapping is a form of Rb depolarization thought to be quenched by the N₂ added to SEOP gas mixtures. Here we use absorption spectroscopy to measure the Rb density, optical spectroscopy to monitor the fraction of Rb atoms involved in radiation trapping, and field cycling to measure the Rb polarization. We find that radiation trapping is still present during spin-exchange optical pumping and appears to limit the achievable Rb polarization.

Jose Santiago Enriquez^1,2, Natalia Baran³, Shivanand Pudakalakatti¹, Marina Konopleva^2,3, and Pratip Bhattacharya^1,2
1Cancer Systems Imaging, MD Anderson Cancer Center, Houston, TX, United States, ²UT MD Anderson Cancer Center UT Health Science Center Houston Graduate School of Biomedical Sciences, Houston, TX, United States, ³Leukemia, MD Anderson Cancer Center, Houston, TX, United States

Metabolic reprogramming is one of the key hallmarks in acquiring aggressive phenotype and chemoresistance in many cancers including T-cell acute lymphoblastic leukemia (T-ALL). To combat chemoresistance, we treated patient-derived xenografts with two metabolic drugs that target two different pathways for T-ALL: IACS-010759, a Complex I inhibitor for OXPHOS pathway and AZD3965, a monocarboxylate transporter-1 (MCT1) inhibitor. Hyperpolarized metabolic imaging in vivo and NMR metabolomics ex vivo was utilized to observe the difference in metabolism with single treatment and in combination. Our results demonstrate that metabolic intervention utilizing OXPHOS blockade can be potentiated by targeting the MCT1 transporter.

Junlan Lu¹, Suphachart Leewiwatwong², David Mummy³, and Bastiaan Driehuys^2
1Medical Physics, Duke University, Durham, NC, United States, ²Biomedical Engineering, Duke University, Durham, NC, United States, ³Radiology, Duke University, Durham, NC, United States

Quantitative analysis of hyperpolarized ¹²⁹Xe ventilation imaging requires overcoming the ill-posed problem of accurately correcting for bias field. The standard solution of N4ITK bias field correction removes not only bias field, but also physiologic gradients of interest. An alternative approach is applying RF depolarization mapping in a cohort of subjects to construct a bias field template. Here, we compare the effect that these different bias field correction techniques have on the ¹²⁹Xe MRI ventilation gradients in a cohort of healthy patients (n=18).

Tahmina Achekzai¹, Luis Loza¹, Stephen Kadlecek¹, Kai Ruppert¹, Faraz Amzajerdian¹, and Rahim Rizi^1
1University of Pennsylvania, Philadelphia, PA, United States

In Xenon Polarization Transfer Constant (XTC) imaging, saturation pulses are applied at DP Xe frequencies for red blood cell (RBC) and tissue plasma (TP), but, due to their high power, are not perfectly selective, often depolarizing both DP frequencies instead of only the one intended. We used XTC spectroscopy to explore how various saturation pulse parameters, primarily pulse power, affects saturation selectivity. The generated graphs plot depolarization as a function of saturation frequency. They demonstrate that as pulse power increases, the contribution of gas-phase depolarization due to off-resonance saturation increases, compromising selectivity.