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James E. Ball¹, Jim M. Wild¹, and Graham Norquay^1
1University of Sheffield, Sheffield, United Kingdom

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Gas)

Accurate knowledge of the Rb vapor density, [Rb], is essential for optimizing ¹²⁹Xe polarization (PXe) and production rates in clinical-scale ¹²⁹Xe-Rb SEOP hyperpolarizers, used for hyperpolarized ¹²⁹Xe MRI. We used atomic absorption spectroscopy to measure [Rb] for multiple Rb transitions to assess [Rb] measurement accuracy and extend [Rb] measurement range sensitivity. It was shown that [Rb] is significantly lower than saturation [Rb] and that [Rb] homogeneity was improved by implementing a larger Rb source distribution or a presaturator. The ¹²⁹Xe-Rb spin-exchange cross section, $$$\gamma^\prime$$$, was determined  to be $$$\gamma^\prime$$$= (1.2± 0.1) ×10⁻²¹m³s⁻¹ for our operating conditions.

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Yohn Taylor¹, Geoffrey J. M. Parker^1,2, Mina Kim¹, and Pilar Jimenez-royo^3
1Centre for Medical Image Computing, Quantitative Imaging Group, Department of Medical Physics & Biomedical Engineering, University College London, London, United Kingdom, ²Bioxydyn Limited, Manchester, United Kingdom, ³GlaxoSmithKline, Stevenege, United Kingdom

Keywords: Hyperpolarized MR (Gas), Modelling, Blind deconvolution

Preclinical to clinical translation of pulmonary gas exchange measurements utilising hyperpolarised ¹²⁹Xe MRI is limited by the overlapping spectral peaks of dissolved ¹²⁹Xe MR red blood cell (RBC) and tissue compartments in some preclinical species. We present a novel kinetic model of ¹²⁹Xe exchange (KMXE) in conjunction with blind estimation techniques to evaluate ¹²⁹Xe exchange between pulmonary tissue and blood without needing an explicit measurement of RBC signals. Using simulations, we show that kinetic parameter estimates are comparable to those estimated using conventional methods, demonstrating feasibility for evaluating gas exchange kinetics when no distinct RBC spectral peak can be measured.

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Mitra Tavakkoli^1,2, Sarah Svenningsen^3,4, Yonni Friedlander⁴, Norm Konyer⁵, Parameswaran Nair^3,4, and Michael D Noseworthy^1,5,6,7
1Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada, ²Imaging Research Centre, St. Joseph's Healthcare, Hamilton, ON, Canada, ³Department of Medicine, McMaster University, Hamilton, ON, Canada, ⁴Firestone Institute for Respiratory Health, St Joseph’s Healthcare Hamilton, Hamilton, ON, Canada, ⁵Imaging Research Centre, St. Joseph’s Healthcare Hamilton, Hamilton, ON, Canada, ⁶Biomedical Engineering, McMaster University, Hamilton, ON, Canada, ⁷Department of Radiology, McMaster University, Hamilton, ON, Canada

Keywords: Image Reconstruction, Sparse & Low-Rank Models, Compressed Sensing, Lung, 129Xenon

Compressed sensing is a fast-imaging technique capable of making high quality images with undersampled data. However, its application in hyperpolarized ¹²⁹Xe diffusion-weighted MRI needs to be optimized. In this study, diffusion weighted images undersampled identically and differently, were compared with SNR, SSIM, mean ADC using repeated measures ANOVA. The application of different undersampling patterns for both diffusion-weighted and baseline images can result in ADC maps with higher quality, as compared to fully sampled equivalent parametric images. Thus, the baseline and diffusion-weighted images do not necessarily have the same optimum undersampling pattern, and optimization of each needs investigation separately.

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Kylie Yeung^1,2,3, Zack Ravetz^1,4, Kher Lik Ng^2,5, Gabriele AbuEid², William Hickes², Kenneth Jacob², Mitchel Danisa², Marianne Durrant², Rebecca Mills¹, Ayaka Shinozaki^1,6, Jordan McGing¹, Aaron Axford¹, Sarah Birkhoelzer¹, Rolf F Schulte⁷, Oliver Rider¹, Anthony McIntyre², Emily Fraser⁵, Damian J Tyler^1,6, Fergus Gleeson^2,8, and James T Grist^1,2,6,9
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom, ²Department of Radiology, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom, ³Department of Oncology, Univeristy of Oxford, Oxford, United Kingdom, ⁴RRPPS, University Hospitals Birmingham, Birmingham, United Kingdom, ⁵Oxford Respiratory Service, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom, ⁶Department of Physiology, Anatomy and Genetics, Univeristy of Oxford, Oxford, United Kingdom, ⁷GE Global Research, Munich, Germany, ⁸Department of Oncology, University of Oxford, Oxford, United Kingdom, ⁹Alama Mater Studorium, University of Bologna, Bologna, Italy

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Non-Gas), Xenon-129, Carbon-13

Hyperpolarized MRI allows the imaging of processes such as gas exchange and metabolism. Calibration of transmit and receive (Tx/Rx) B₁ is required to account for coil inhomogeneities in reconstruction. A variable flip angle (VFA) method, which is fast and readily implemented, allows for a simultaneous B₁/T₁ measurement. In this study, a mathematical model of VFA calibration was developed, tested, validated in a hyperpolarized Carbon-13 (¹³C) phantom and in vivo with hyperpolarized Xenon-129 imaging of human lungs.

Cheng Wang^1,2, Sa Xiao^1,2, Zimeng Li^1,2, Haidong Li^1,2, and Xin Zhou^1,2
1State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Wuhan, China, ²University of Chinese Academy of Sciences, Beijing, China

Keywords: Hyperpolarized MR (Gas), Lung

Ventilation defect percentage (VDP) generated from hyperpolarized gas (³He or ¹²⁹Xe) MRI is a sensitive indicator of lung disease. However, the commonly used K-means method for the calculation of VDP is not suitable for low signal-to-noise ratio (SNR) images. In this work, we proposed a hybrid segmentation method to segment the ventilation defect regions and calculate VDP values under low SNR conditions. The results show that the proposed method has improved both the accuracy of segmenting VDP map and calculating VDP value.

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Aryil Bechtel¹, David Mummy¹, Junlan Lu², Suphachart Leewiwatwong³, Joseph Mammarappallil¹, Sakib Kabir¹, and Bastiaan Driehuys^1,2,3
1Radiology, Duke University, Durham, NC, United States, ²Medical Physics, Duke University, Durham, NC, United States, ³Biomedical Engineering, Duke University, Durham, NC, United States

Keywords: Hyperpolarized MR (Gas), Lung

¹²⁹Xe gas exchange MRI is commonly quantified by binning images of ventilation, membrane uptake (M/gas), and red blood cell transfer (RBC/gas) according to thresholds established using healthy reference distributions. To date, reference values have been based on small samples and do not account for hemoglobin concentration (Hb), which is known to vary by sex. We apply a Hb correction to data from 15 young, healthy volunteers (age=25.2±3.3 yrs., 6 female). After correction, there was no significant difference in individual mean M/gas and RBC/gas between males and females. The resulting reference distributions have less dispersion and skew than previously established distributions.

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Neil J Stewart¹, Jose de Arcos², Alberto M Biancardi¹, Jemima H Pilgrim-Morris¹, Oliver I Rodgers¹, Ryan S Munro¹, Guilhem J Collier¹, Graham Norquay¹, Helen Marshall¹, Anja Brau³, Marc Lebel⁴, and Jim M Wild^1
1The University of Sheffield, Sheffield, United Kingdom, ²GE Healthcare, Cambridge, United Kingdom, ³GE Healthcare, San Francisco, CA, United States, ⁴GE Healthcare, Calgary, AB, Canada

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Gas)

The utility of a deep learning based reconstruction tool for improving the quality of hyperpolarized ¹²⁹Xe lung ventilation images was assessed. DL-reconstructed ¹²⁹Xe ventilation image quality and SNR was improved compared with conventionally reconstructed images. In a cohort of patients with asthma and/or COPD, a small bias towards increased ventilation defect percentage, and a bias towards decreased coefficient of variation, in DL-reconstructed vs. conventionally-reconstructed images, was observed. Initial feasibility of utilising this tool for reduced-cost ¹²⁹Xe ventilation imaging using natural-abundance xenon, and improved spatial resolution imaging with 129-enriched xenon, is demonstrated.

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Paulina Victoria Wyszkiewicz^1,2, Maksym Sharma^1,2, Harkiran K Kooner^1,2, David G McCormack³, Miranda Kirby⁴, and Grace Parraga^1,2,3,5
1Department of Medical Biophysics, Western University, London, ON, Canada, ²Robarts Research Institute, London, ON, Canada, ³Division of Respirology, Department of Medical Biophysics, Western University, London, ON, Canada, ⁴Department of Physics, Toronto Metropolitan University, Toronto, ON, Canada, ⁵School of Biomedical Engineering, Western University, London, ON, Canada

Keywords: Hyperpolarized MR (Gas), Lung

The onset and progression of chronic obstructive pulmonary disease (COPD) is currently believed to initiate in the small-airways and progresses to emphysema or terminal airspace (alveolar) enlargement and destruction. MRI apparent-diffusion-coefficient (ADC) provides a way to measure subclinical emphysematous destruction in patients. Here we investigated the relationship between pulmonary functional MRI measurements of terminal airspace enlargement using ³He MRI-ADC and CT airway changes in ex-smokers with COPD. MRI-ADC values at baseline were uniquely predictive of worsening CT total-airway-count and airway wall-area after three-years. MRI captures evidence of mild or subclinical emphysema and its relationship with terminal airway obliteration in COPD.
 

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Lutoslawa Mikowska¹, Vira Grynko^2,3, Yurii Shepelytskyi^3,4, Iullian Constantin Ruset⁵, Joseph Deschamps⁶, Hannah Aalto⁶, Marta Targosz-Korecka¹, Hubert Harańczyk¹, Dilip Balamore⁷, and Mitchell Albert^3,4,8
1Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Kraków, Poland, ²Chemistry and Material Science Program, Lakehead University, Thunder Bay, ON, Canada, ³Thunder Bay Regional Health Research Institute, Thunder Bay, ON, Canada, ⁴Chemistry Department, Lakehead University, Thunder Bay, ON, Canada, ⁵Xemed LLC, Durham, NH, United States, ⁶Applied Life Sciences Program, Lakehead University, Thunder Bay, ON, Canada, ⁷Department of Engineering/Physics/Technology, Nassau Community College, Garden City, NY, United States, ⁸Northern Ontario School of Medicine, Sudbury, ON, Canada

Keywords: Hyperpolarized MR (Gas), Spectroscopy, blood, hemoglobin, dissolved phase imaging

We examined the impact of elevated glucose levels on the chemical shift and T₂^* relaxation of hyperpolarized ¹²⁹Xe dissolved in sheep blood. The addition of glucose did not affect the ¹²⁹Xe-plasma resonance. For the first time, however, we have observed an additional ¹²⁹Xe dissolved phase resonance attributed to ¹²⁹Xe bound to glycated hemoglobin. A glucose-related linear downfield shift of the ¹²⁹Xe resonance frequency was observed for ¹²⁹Xe bound to native hemoglobin, whereas the T₂^* relaxation of ¹²⁹Xe bound to glycated hemoglobin increased non-linearly with increasing glucose concentration.

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Michele Kelley¹, Nicholas Bryden¹, Sebastian William Atalla¹, and Rosa Tamara Branca^1
1University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Gas)

We present a simple protocol for polarizing ¹H at ultra-low field. By simply bubbling hyperpolarized Xe gas in a solution containing thermally polarized ¹H spins, the proton thermal polarization can be enhanced by more than 100-fold. This enhancement is clearly observed, even in absence of saturation pulses, at ultra-low field where thermal polarization is close to background noise levels. Simultaneous detection of ¹H and ¹²⁹Xe magnetizations shows that the transfer of polarization from ¹²⁹Xe to ¹H spins is a continuous process that lasts until the dissolved-phase ¹²⁹Xe polarization is relaxed back to thermal equilibrium. 

Chenlu Yuan¹, Qianni Guo¹, Qingbin Zeng¹, Yaping Yuan¹, Weiping Jiang¹, Chaohui Ye¹, and Xin Zhou^1
1Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences – Wuhan National Laboratory for Optoelectronics, Wuhan 430071, P. R. China, WUHAN, China

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Gas), 129Xe，Hyper-CEST

We synthesized an ultrasensitive ¹²⁹Xe NMR probe with dual signals. It is a hollow nanoparticle composed of water-soluble CB[6]. It has two different hydrophobic cavities. Two ¹²⁹Xe NMR signals with different chemical shifts can appear in a single detection, effectively avoiding the occurrence of false positive and false negative in complex biological environment detection, improving the accuracy and sensitivity of single detection, and has broad application prospects.

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Michael Vaeggemose^1,2, Graham Norquay ³, Esben Søvsø Szocska Hansen¹, Neil J. Stewart³, Oliver I. Rodgers³, Ryan S. Munro³, Rolf F. Schulte⁴, Guilhem J. Collier ³, Christoffer Laustsen¹, and Jim M. Wild^3
1MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark, ²GE Healthcare, Brøndby, Denmark, ³POLARIS group, University of Sheffield, Sheffield, United Kingdom, ⁴GE Healthcare, Munich, Germany

Keywords: Hyperpolarized MR (Gas), Hyperpolarized MR (Gas), Lung ventilation imaging

Hyperpolarised ¹²⁹Xe gas was accumulated using spin-exchange optical pumping (SEOP) by continuous-flow of xenon gas directly from the cell without the use of cryogenic separation. 3D ventilation images were acquired in human and porcine models to determine clinical diagnostic image quality. Xenon ventilation image quality indicates that on demand batch production of xenon is feasible for both preclinical and clinical lung ventilation imaging examinations.

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Aryil Bechtel¹, Anna Costelle², Elianna Bier³, Junlan Lu², Joseph Mammarappallil¹, Sakib Kabir¹, David Mummy¹, and Bastiaan Driehuys^1,2,3
1Radiology, Duke University, Durham, NC, United States, ²Medical Physics, Duke University, Durham, NC, United States, ³Biomedical Engineering, Duke University, Durham, NC, United States

Keywords: Hyperpolarized MR (Gas), Heart, Lung

¹²⁹Xe MRS measures static and dynamic spectral parameters from ¹²⁹Xe signal in airspaces, membrane tissues, and red blood cells (RBC) and has the potential to characterize cardiopulmonary diseases. However, a better understanding of measurement repeatability is needed, and different approaches to quantifying cardiogenic oscillations have been proposed. Here, we compare quantification of oscillations using sine-fitting and a peak-finding algorithm and use reader ratings to identify acceptable study quality. Across a range of cardiopulmonary disease groups, measurements of static parameters showed good intra-session repeatability while the peak-finding algorithm generally yielded higher repeatability than sine fits for most dynamic parameters.

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Kai Ruppert¹, Luis Loza¹, Faraz Amzajerdian¹, Hooman Hamedani¹, Mostafa K Ismail¹, Ryan J Baron¹, Ian F Duncan¹, Harrilla Profka¹, Stephen Kadlecek¹, and Rahim R Rizi^1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States

Keywords: Hyperpolarized MR (Gas), Pulse Sequence Design

Chemical shift saturation recovery (CSSR) MR spectroscopy using hyperpolarized xenon-129 provides metrics of pulmonary physiology by saturating the xenon dissolved-phase magnetization in the lung with a 90° RF pulse and measuring the subsequent signal recovery via gas exchange. Our measurements in a rat demonstrate that chemical shift inversion recovery (CSIR) spectroscopy, which replaces the saturation with an inversion pulse, produces equivalent results to CSSR but with greater robustness with respect to both low signal amplitudes at short delay times and incomplete saturation.

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Faraz Amzajerdian¹, Hooman Hamedani¹, Ryan Baron¹, Mostafa Ismail¹, Luis Loza¹, Kai Ruppert¹, Stephen Kadlecek¹, and Rahim Rizi^1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States

Keywords: Hyperpolarized MR (Gas), Lung

Regional quantification of ventilation dynamics can provide valuable insights into the functional changes associated with both unilateral and bilateral lung transplantation, potentially improving diagnostic monitoring and providing a better understanding of underlying pathophysiology. By imaging hyperpolarized xenon-129 (HXe) continuously over an extended period of time, ventilation dynamics more representative of steady-state, physiological breathing were derived and used to assess differences between unilateral and bilateral transplant patients.

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Nicholas Bryden¹, Sebastian William Atalla¹, Michele Kelley¹, Leah R Holmes¹, and Rosa Tamara Branca^1
1Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Keywords: Hyperpolarized MR (Non-Gas), Relaxometry

We demonstrate enhanced T₁ relaxation of hyperpolarized ¹²⁹Xe spins in blood and in the presence of superparamagnetic iron oxide nanoparticles (SPIONs) at low field strengths.