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Rapid pulmonary 129Xe ventilation MRI of discharged COVID-19 patients with zigzag sampling. Magn Reson Med 2024. [PMID: 38770624 DOI: 10.1002/mrm.30120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 03/05/2024] [Accepted: 04/02/2024] [Indexed: 05/22/2024]
Abstract
PURPOSE To demonstrate the feasibility of zigzag sampling for 3D rapid hyperpolarized 129Xe ventilation MRI in human. METHODS Zigzag sampling in one direction was combined with gradient-recalled echo sequence (GRE-zigzag-Y) to acquire hyperpolarized 129Xe ventilation images. Image quality was compared with a balanced SSFP (bSSFP) sequence with the same spatial resolution for 12 healthy volunteers (HVs). For another 8 HVs and 9 discharged coronavirus disease 2019 subjects, isotropic resolution 129Xe ventilation images were acquired using zigzag sampling in two directions through GRE-zigzag-YZ. 129Xe ventilation defect percent (VDP) was quantified for GRE-zigzag-YZ and bSSFP acquisitions. Relationships and agreement between these VDP measurements were evaluated using Pearson correlation coefficient (r) and Bland-Altman analysis. RESULTS For 12 HVs, GRE-zigzag-Y and bSSFP required 2.2 s and 10.5 s, respectively, to acquire 129Xe images with a spatial resolution of 3.96 × 3.96 × 10.5 mm3. Structural similarity index, mean absolute error, and Dice similarity coefficient between the two sets of images and ventilated lung regions were 0.85 ± 0.03, 0.0015 ± 0.0001, and 0.91 ± 0.02, respectively. For another 8 HVs and 9 coronavirus disease 2019 subjects, 129Xe images with a nominal spatial resolution of 2.5 × 2.5 × 2.5 mm3 were acquired within 5.5 s per subject using GRE-zigzag-YZ. VDP provided by GRE-zigzag-YZ was strongly correlated (R2 = 0.93, p < 0.0001) with that generated by bSSFP with minimal biases (bias = -0.005%, 95% limit-of-agreement = [-0.414%, 0.424%]). CONCLUSION Zigzag sampling combined with GRE sequence provides a way for rapid 129Xe ventilation imaging.
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Hyperpolarized 129Xe MRI, 99mTc scintigraphy, and SPECT in lung ventilation imaging: a quantitative comparison. Acad Radiol 2024; 31:1666-1675. [PMID: 37977888 PMCID: PMC11015986 DOI: 10.1016/j.acra.2023.10.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/22/2023] [Accepted: 10/22/2023] [Indexed: 11/19/2023]
Abstract
RATIONALE AND OBJECTIVES The current clinical standard for functional imaging of patients with lung ailments is nuclear medicine scintigraphy and Single Photon Emission Computed Tomography (SPECT) which detect the gamma decay of inhaled radioactive tracers. Hyperpolarized (HP) Xenon-129 MRI (XeMRI) of the lungs has recently been FDA approved and provides similar functional images of the lungs with higher spatial resolution than scintigraphy and SPECT. Here we compare Technetium-99m (99mTc) diethylene-triamine-pentaacetate scintigraphy and SPECT with HP XeMRI in healthy controls, asthma, and chronic obstructive pulmonary disorder (COPD) patients. MATERIALS AND METHODS 59 subjects, healthy, with asthma, and with COPD, underwent 99mTc scintigraphy/SPECT, standard spirometry, and HP XeMRI. XeMRI and SPECT images were registered for direct voxel-wise signal comparisons. Images were also compared using ventilation defect percentage (VDP), and a standard 6-compartment method. VDP calculated from XeMRI and SPECT images was compared to spirometry. RESULTS Median Pearson correlation coefficient for voxel-wise signal comparison was 0.698 (0.613-0.782) between scintigraphy and XeMRI and 0.398 (0.286-0.502) between SPECT and XeMRI. Correlation between VDP measures was r = 0.853, p < 0.05. VDP separated asthma and COPD from the control group and was significantly correlated with FEV1, FEV1/FVC, and FEF 25-75. CONCLUSION HP XeMRI provides equivalent information to 99mTc SPECT and standard spirometry measures. Additionally, XeMRI is non-invasive, hence it could be used for longitudinal studies for evaluating emerging treatment for lung ailments.
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Effects of inhaled low-concentration xenon gas on naltrexone-precipitated withdrawal symptoms in morphine-dependent mice. Drug Alcohol Depend 2024; 255:110967. [PMID: 38150894 PMCID: PMC10841182 DOI: 10.1016/j.drugalcdep.2023.110967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 12/29/2023]
Abstract
BACKGROUND Opioid withdrawal symptoms (OWS) are highly aversive and prompt unprescribed opioid use, which increases morbidity, mortality, and, among individuals being treated for opioid use disorder (OUD), recurrence. OWS are driven by sympathetic nervous system (SNS) hyperactivity that occurs when blood opioid levels wane. We tested whether brief inhalation of xenon gas, which inhibits SNS activity and is used clinically for anesthesia and diagnostic imaging, attenuates naltrexone-precipitated withdrawal-like signs in morphine-dependent mice. METHODS Adult CD-1 mice were implanted with morphine sulfate-loaded (60 mg/ml) minipumps and maintained for 6 days to establish morphine dependence. On day 7, mice were given subcutaneous naltrexone (0.3 mg/kg) and placed in a sealed exposure chamber containing either 21% oxygen/balance nitrogen (controls) or 21% oxygen/added xenon peaking at 30%/balance nitrogen. After 10 minutes, mice were transferred to observation chambers and videorecorded for 45 minutes. Videos were scored in a blind manner for morphine withdrawal behaviors. Data were analyzed using 2-way ANOVAs testing for treatment and sex effects. RESULTS AND CONCLUSIONS Xenon-exposed mice exhibited fewer jumps (P = 0.010) and jumping suppression was detectible within the first 10-minute video segment, but no sex differences were detected. Brief inhalation of low concentration xenon rapidly and substantially attenuated naltrexone-precipitated jumping in morphine-dependent mice, suggesting that it can inhibit OWS. If xenon effects translate to humans with OUD, xenon inhalation may be effective for reducing OWS, unprescribed opioid use, and for easing OUD treatment initiation, which could help lower excess morbidity and mortality associated with OUD.
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Initial feasibility and challenges of hyperpolarized 129 Xe MRI in neonates with bronchopulmonary dysplasia. Magn Reson Med 2023; 90:2420-2431. [PMID: 37526031 PMCID: PMC10629838 DOI: 10.1002/mrm.29808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/14/2023] [Accepted: 07/08/2023] [Indexed: 08/02/2023]
Abstract
PURPOSE The underlying functional and microstructural lung disease in neonates who are born preterm (bronchopulmonary dysplasia, BPD) remains poorly characterized. Moreover, there is a lack of suitable techniques to reliably assess lung function in this population. Here, we report our preliminary experience with hyperpolarized 129 Xe MRI in neonates with BPD. METHODS Neonatal intensive care patients with established BPD were recruited (N = 9) and imaged at a corrected gestational age of median:40.7 (range:37.1, 44.4) wk using a 1.5T neonatal scanner. 2D 129 Xe ventilation and diffusion-weighted images and dissolved phase spectroscopy were acquired, alongside 1 H 3D radial UTE. 129 Xe images were acquired during a series of short apneic breath-holds (˜3 s). 1 H UTE images were acquired during tidal breathing. Ventilation defects were manually identified and qualitatively compared to lung structures on UTE. ADCs were calculated on a voxel-wise basis. The signal ratio of the 129 Xe red blood cell (RBC) and tissue membrane (M) resonances from spectroscopy was determined. RESULTS Spiral-based 129 Xe ventilation imaging showed good image quality and sufficient sensitivity to detect mild ventilation abnormalities in patients with BPD. 129 Xe ADC values were elevated above that expected given healthy data in older children and adults (median:0.046 [range:0.041, 0.064] cm2 s-1 ); the highest value obtained from an extremely pre-term patient. 129 Xe spectroscopy revealed a low RBC/M ratio (0.14 [0.06, 0.21]). CONCLUSION We have demonstrated initial feasibility of 129 Xe lung MRI in neonates. With further data, the technique may help guide management of infant lung diseases in the neonatal period and beyond.
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Functional lung imaging using novel and emerging MRI techniques. Front Med (Lausanne) 2023; 10:1060940. [PMID: 37181360 PMCID: PMC10166823 DOI: 10.3389/fmed.2023.1060940] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 04/03/2023] [Indexed: 05/16/2023] Open
Abstract
Respiratory diseases are leading causes of death and disability in the world. While early diagnosis is key, this has proven difficult due to the lack of sensitive and non-invasive tools. Computed tomography is regarded as the gold standard for structural lung imaging but lacks functional information and involves significant radiation exposure. Lung magnetic resonance imaging (MRI) has historically been challenging due to its short T2 and low proton density. Hyperpolarised gas MRI is an emerging technique that is able to overcome these difficulties, permitting the functional and microstructural evaluation of the lung. Other novel imaging techniques such as fluorinated gas MRI, oxygen-enhanced MRI, Fourier decomposition MRI and phase-resolved functional lung imaging can also be used to interrogate lung function though they are currently at varying stages of development. This article provides a clinically focused review of these contrast and non-contrast MR imaging techniques and their current applications in lung disease.
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Undersampled Diffusion-Weighted 129Xe MRI Morphometry of Airspace Enlargement: Feasibility in Chronic Obstructive Pulmonary Disease. Diagnostics (Basel) 2023; 13:diagnostics13081477. [PMID: 37189579 DOI: 10.3390/diagnostics13081477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/10/2023] [Accepted: 04/18/2023] [Indexed: 05/17/2023] Open
Abstract
Multi-b diffusion-weighted hyperpolarized gas MRI measures pulmonary airspace enlargement using apparent diffusion coefficients (ADC) and mean linear intercepts (Lm). Rapid single-breath acquisitions may facilitate clinical translation, and, hence, we aimed to develop single-breath three-dimensional multi-b diffusion-weighted 129Xe MRI using k-space undersampling. We evaluated multi-b (0, 12, 20, 30 s/cm2) diffusion-weighted 129Xe ADC/morphometry estimates using a fully sampled and retrospectively undersampled k-space with two acceleration-factors (AF = 2 and 3) in never-smokers and ex-smokers with chronic obstructive pulmonary disease (COPD) or alpha-one anti-trypsin deficiency (AATD). For the three sampling cases, mean ADC/Lm values were not significantly different (all p > 0.5); ADC/Lm values were significantly different for the COPD subgroup (0.08 cm2s-1/580 µm, AF = 3; all p < 0.001) as compared to never-smokers (0.05 cm2s-1/300 µm, AF = 3). For never-smokers, mean differences of 7%/7% and 10%/7% were observed between fully sampled and retrospectively undersampled (AF = 2/AF = 3) ADC and Lm values, respectively. For the COPD subgroup, mean differences of 3%/4% and 11%/10% were observed between fully sampled and retrospectively undersampled (AF = 2/AF = 3) ADC and Lm, respectively. There was no relationship between acceleration factor with ADC or Lm (p = 0.9); voxel-wise ADC/Lm measured using AF = 2 and AF = 3 were significantly and strongly related to fully-sampled values (all p < 0.0001). Multi-b diffusion-weighted 129Xe MRI is feasible using two different acceleration methods to measure pulmonary airspace enlargement using Lm and ADC in COPD participants and never-smokers.
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B 1 and magnetization decay correction for hyperpolarized 129 Xe lung imaging using sequential 2D spiral acquisitions. Magn Reson Med 2023; 90:473-482. [PMID: 36989185 DOI: 10.1002/mrm.29655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/22/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023]
Abstract
PURPOSE To mitigate signal variations caused by inhomogeneous RF and magnetization decay in hyperpolarized 129 Xe ventilation images using flip-angle maps generated from sequential 2D spiral ventilation images acquired in a breath-hold. Images and correction maps were compared with those obtained using conventional, 2D gradient-recalled echo. THEORY AND METHODS Analytical expressions to predict signal intensity and uncertainty in flip-angle measurements were derived from the Bloch equations and validated by simulations and phantom experiments. Imaging in 129 Xe phantoms and human subjects (1 healthy, 1 cystic fibrosis) was performed using 2D gradient-recalled echo and spiral. For both sequences, consecutive images were acquired with the same slice position during a breath-hold (Cartesian scan time = 15 s; spiral scan time = 5 s). The ratio of these images was used to calculate flip-angle maps and correct intensity inhomogeneities in ventilation images. RESULTS Mean measured flip angle showed excellent agreement with the applied flip angle in simulations (R2 = 0.99) for both sequences. Mean measured flip angle agreed well with the globally applied flip angle (∼15% difference) in 129 Xe phantoms and in vivo imaging using both sequences. Corrected images displayed reduced coil-dependent signal nonuniformity relative to uncorrected images. CONCLUSIONS Flip-angle maps were obtained using sequentially acquired, 2D spiral, 129 Xe ventilation images. Signal intensity variations caused by RF-coil inhomogeneity can be corrected by acquiring sequential single-breath ventilation images in less than 5-s scan time. Thus, this method can be used to remove undesirable heterogeneity while preserving physiological effects on the signal distribution.
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Hyperpolarized 129Xe MRI at low field: Current status and future directions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 348:107387. [PMID: 36731353 DOI: 10.1016/j.jmr.2023.107387] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 12/07/2022] [Accepted: 01/23/2023] [Indexed: 06/18/2023]
Abstract
Magnetic Resonance Imaging (MRI) is dictated by the magnetization of the sample, and is thus a low-sensitivity imaging method. Inhalation of hyperpolarized (HP) noble gases, such as helium-3 and xenon-129, is a non-invasive, radiation-risk free imaging technique permitting high resolution imaging of the lungs and pulmonary functions, such as the lung microstructure, diffusion, perfusion, gas exchange, and dynamic ventilation. Instead of increasing the magnetic field strength, the higher spin polarization achievable from this method results in significantly higher net MR signal independent of tissue/water concentration. Moreover, the significantly longer apparent transverse relaxation time T2* of these HP gases at low magnetic field strengths results in fewer necessary radiofrequency (RF) pulses, permitting larger flip angles; this allows for high-sensitivity imaging of in vivo animal and human lungs at conventionally low (<0.5 T) field strengths and suggests that the low field regime is optimal for pulmonary MRI using hyperpolarized gases. In this review, theory on the common spin-exchange optical-pumping method of hyperpolarization and the field dependence of the MR signal of HP gases are presented, in the context of human lung imaging. The current state-of-the-art is explored, with emphasis on both MRI hardware (low field scanners, RF coils, and polarizers) and image acquisition techniques (pulse sequences) advancements. Common challenges surrounding imaging of HP gases and possible solutions are discussed, and the future of low field hyperpolarized gas MRI is posed as being a clinically-accessible and versatile imaging method, circumventing the siting restrictions of conventional high field scanners and bringing point-of-care pulmonary imaging to global facilities.
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Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report. Ann Am Thorac Soc 2023; 20:161-195. [PMID: 36723475 PMCID: PMC9989862 DOI: 10.1513/annalsats.202211-915st] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MRI) using ultrashort-echo time (UTE) sequences has improved signal detection from lung parenchyma; contrast agents are used to deduce airway function, ventilation-perfusion-diffusion, and mechanics. Proton MRI can measure regional ventilation-perfusion ratio. Quantitative imaging (QI)-derived endpoints have been developed to identify structure-function phenotypes, including air-blood-tissue volume partition, bronchovascular remodeling, emphysema, fibrosis, and textural patterns indicating architectural alteration. Coregistered landmarks on paired images obtained at different lung volumes are used to infer airway caliber, air trapping, gas and blood transport, compliance, and deformation. This document summarizes fundamental "good practice" stereological principles in QI study design and analysis; evaluates technical capabilities and limitations of common imaging modalities; and assesses major QI endpoints regarding underlying assumptions and limitations, ability to detect and stratify heterogeneous, overlapping pathophysiology, and monitor disease progression and therapeutic response, correlated with and complementary to, functional indices. The goal is to promote unbiased quantification and interpretation of in vivo imaging data, compare metrics obtained using different QI modalities to ensure accurate and reproducible metric derivation, and avoid misrepresentation of inferred physiological processes. The role of imaging-based computational modeling in advancing these goals is emphasized. Fundamental principles outlined herein are critical for all forms of QI irrespective of acquisition modality or disease entity.
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Investigating the impact of RF saturation-pulse parameters on compartment-selective gas-phase depolarization with xenon polarization transfer contrast MRI. Magn Reson Med 2022; 88:2447-2460. [PMID: 36046917 PMCID: PMC9529921 DOI: 10.1002/mrm.29405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/20/2022] [Accepted: 07/17/2022] [Indexed: 11/07/2022]
Abstract
PURPOSE To demonstrate the utility of continuous-wave (CW) saturation pulses in xenon-polarization transfer contrast (XTC) MRI and MRS, to investigate the selectivity of CW pulses applied to dissolved-phase resonances, and to develop a correction method for measurement biases from saturation of the nontargeted dissolved-phase compartment. METHODS Studies were performed in six healthy Sprague-Dawley rats over a series of end-exhale breath holds. Discrete saturation schemes included a series of 30 Gaussian pulses (8 ms FWHM), spaced 25 ms apart; CW saturation schemes included single block pulses, with variable flip angle and duration. In XTC imaging, saturation pulses were applied on both dissolved-phase resonance frequencies and off-resonance, to correct for other sources of signal loss and compromised selectivity. In spectroscopy experiments, saturation pulses were applied at a set of 19 frequencies spread out between 185 and 200 ppm to map out modified z-spectra. RESULTS Both modified z-spectra and imaging results showed that CW RF pulses offer sufficient depolarization and improved selectivity for generating contrast between presaturation and postsaturation acquisitions. A comparison of results obtained using a variety of saturation parameters confirms that saturation pulses applied at higher powers exhibit increased cross-contamination between dissolved-phase resonances. CONCLUSION Using CW RF saturation pulses in XTC contrast preparation, with the proposed correction method, offers a potentially more selective alternative to traditional discrete saturation. The suppression of the red blood cell contribution to the gas-phase depolarization opens the door to a novel way of quantifying exchange time between alveolar volume and hemoglobin.
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MR Imaging for the Evaluation of Diffuse Lung Disease. Radiol Clin North Am 2022; 60:1021-1032. [DOI: 10.1016/j.rcl.2022.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pediatric 129 Xe Gas-Transfer MRI-Feasibility and Applicability. J Magn Reson Imaging 2022; 56:1207-1219. [PMID: 35244302 PMCID: PMC9519191 DOI: 10.1002/jmri.28136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 02/16/2022] [Accepted: 02/18/2022] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND 129 Xe gas-transfer MRI provides regional measures of pulmonary gas exchange in adults and separates xenon in interstitial lung tissue/plasma (barrier) from xenon in red blood cells (RBCs). The technique has yet to be demonstrated in pediatric populations or conditions. PURPOSE/HYPOTHESIS To perform an exploratory analysis of 129 Xe gas-transfer MRI in children. STUDY TYPE Prospective. POPULATION Seventy-seven human volunteers (38 males, age = 17.7 ± 15.1 years, range 5-68 years, 16 healthy). Four pediatric disease cohorts. FIELD STRENGTH/SEQUENCE 3-T, three-dimensional-radial one-point Dixon Fast Field Echo (FFE) Ultrashort Echo Time (UTE). ASSESSMENT Breath hold compliance was assessed by quantitative signal-to-noise and dynamic metrics. Whole-lung means and standard deviations were extracted from gas-transfer maps. Gas-transfer metrics were investigated with respect to age and lung disease. Clinical pulmonary function tests were retrospectively acquired for reference lung disease severity. STATISTICAL TESTS Wilcoxon rank-sum tests to compare age and disease cohorts, Wilcoxon signed-rank tests to compare pre- and post-breath hold vitals, Pearson correlations between age and gas-transfer metrics, and limits of normal with a binomial exact test to compare fraction of subjects with abnormal gas-transfer. P ≤ 0.05 was considered significant. RESULTS Eighty percentage of pediatric subjects successfully completed 129 Xe gas-transfer MRI. Gas-transfer parameters differed between healthy children and adults, including ventilation (0.75 and 0.67) and RBC:barrier ratio (0.31 and 0.46) which also correlated with age (ρ = -0.76, 0.57, respectively). Bone marrow transplant subjects had impaired ventilation (90% of reference) and increased dissolved 129 Xe standard deviation (242%). Bronchopulmonary dysplasia subjects had decreased barrier-uptake (69%). Cystic fibrosis subjects had impaired ventilation (91%) and increased RBC-transfer (146%). Lastly, childhood interstitial lung disease subjects had increased ventilation heterogeneity (113%). Limits of normal provided detection of abnormalities in additional gas-transfer parameters. DATA CONCLUSION Pediatric 129 Xe gas-transfer MRI was adequately successful and gas-transfer metrics correlated with age. Exploratory analysis revealed abnormalities in a variety of pediatric obstructive and restrictive lung diseases. LEVEL OF EVIDENCE 2 TECHNICAL EFFICACY STAGE: 2.
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Nichtinvasive funktionelle Lungenbildgebung mit hyperpolarisiertem Xenon. ZEITSCHRIFT FÜR PNEUMOLOGIE 2022. [PMCID: PMC9387426 DOI: 10.1007/s10405-022-00462-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hintergrund Die Magnetresonanztomographie (MRT) ist ein nichtinvasives Verfahren mit hervorragendem Weichteilkontrast. Aufgrund der geringen Protonendichte und vielen Luft-Gewebe-Übergängen ist die Anwendung in der Lunge jedoch eingeschränkt, so dass hier häufig röntgenbasierte Methoden eingesetzt werden (mit den bekannten Nachteilen ionisierender Strahlung). Fragestellung In dieser Übersichtsarbeit wird die Lungen-MRT mit hyperpolarisiertem Xenon-129 (Xe-MRT) dargestellt. Die Xe-MRT erlaubt einzigartige wertvolle Einblicke in die Mikrostruktur und Funktion der Lunge, einschließlich des Gasaustauschs mit roten Blutkörperchen – Parameter, die mit klinischen Standardmethoden nicht zugänglich sind. Material und Methoden Durch die magnetische Markierung, die Hyperpolarisierung, wird das Signal von Xenon-129 um bis zu 100.000-fach verstärkt. Hierbei werden die Elektronen von Rubidium mittels Laserlicht zunächst auf 100 % polarisiert und dann durch Stöße auf Xenon übertragen. Danach wird das hyperpolarisierte Gas in einem Beutel zum Patienten gebracht und eingeatmet, kurz bevor die MRT-Aufnahmen beginnen. Ergebnisse Durch spezielle Programmierungen (Sequenzen) in der MRT kann die Ventilation, Mikrostruktur oder der Gasaustausch der Lunge in 3‑D dargestellt werden. Dies ermöglicht z. B. die quantitative Darstellung von Belüftungsdefekten, der Größe der Alveolen, der Gasaufnahme im Gewebe und des Gastransfers ins Blut. Schlussfolgerung Die Xe-MRT liefert einzigartige Informationen über den Zustand der Lunge – nichtinvasiv, in vivo und in weniger als einer Minute.
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Abstract
There is an increased appreciation for the importance of the right heart and pulmonary circulation in several disease states across the spectrum of pulmonary hypertension and left heart failure. However, assessment of the structure and function of the right heart and pulmonary circulation can be challenging, due to the complex geometry of the right ventricle, comorbid pulmonary airways and parenchymal disease, and the overlap of hemodynamic abnormalities with left heart failure. Several new and evolving imaging modalities interrogate the right heart and pulmonary circulation with greater diagnostic precision. Echocardiographic approaches such as speckle-tracking and 3-dimensional imaging provide detailed assessments of regional systolic and diastolic function and volumetric assessments. Magnetic resonance approaches can provide high-resolution views of cardiac structure/function, tissue characterization, and perfusion through the pulmonary vasculature. Molecular imaging with positron emission tomography allows an assessment of specific pathobiologically relevant targets in the right heart and pulmonary circulation. Machine learning analysis of high-resolution computed tomographic lung scans permits quantitative morphometry of the lung circulation without intravenous contrast. Inhaled magnetic resonance imaging probes, such as hyperpolarized 129Xe magnetic resonance imaging, report on pulmonary gas exchange and pulmonary capillary hemodynamics. These approaches provide important information on right ventricular structure and function along with perfusion through the pulmonary circulation. At this time, the majority of these developing technologies have yet to be clinically validated, with few studies demonstrating the utility of these imaging biomarkers for diagnosis or monitoring disease. These technologies hold promise for earlier diagnosis and noninvasive monitoring of right heart failure and pulmonary hypertension that will aid in preclinical studies, enhance patient selection and provide surrogate end points in clinical trials, and ultimately improve bedside care.
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Nichtinvasive funktionelle Lungenbildgebung mit hyperpolarisiertem Xenon. Radiologe 2022; 62:475-485. [PMID: 35403905 PMCID: PMC8996207 DOI: 10.1007/s00117-022-00993-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2022] [Indexed: 11/25/2022]
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Abstract
The use of pulmonary MRI in a clinical setting has historically been limited. Whilst CT remains the gold-standard for structural lung imaging in many clinical indications, technical developments in ultrashort and zero echo time MRI techniques are beginning to help realise non-ionising structural imaging in certain lung disorders. In this invited review, we discuss a complementary technique - hyperpolarised (HP) gas MRI with inhaled 3He and 129Xe - a method for functional and microstructural imaging of the lung that has great potential as a clinical tool for early detection and improved understanding of pathophysiology in many lung diseases. HP gas MRI now has the potential to make an impact on clinical management by enabling safe, sensitive monitoring of disease progression and response to therapy. With reference to the significant evidence base gathered over the last two decades, we review HP gas MRI studies in patients with a range of pulmonary disorders, including COPD/emphysema, asthma, cystic fibrosis, and interstitial lung disease. We provide several examples of our experience in Sheffield of using these techniques in a diagnostic clinical setting in challenging adult and paediatric lung diseases.
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Examining lung microstructure using
19
F MR
diffusion imaging in
COPD
patients. Magn Reson Med 2022; 88:860-870. [DOI: 10.1002/mrm.29237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/24/2022] [Accepted: 02/26/2022] [Indexed: 12/16/2022]
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Imaging in Asthma Management. Semin Respir Crit Care Med 2022; 43:613-626. [PMID: 35211923 DOI: 10.1055/s-0042-1743289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Asthma is a heterogeneous disease characterized by chronic airway inflammation that affects more than 300 million people worldwide. Clinically, asthma has a widely variable presentation and is defined based on a history of respiratory symptoms alongside airflow limitation. Imaging is not needed to confirm a diagnosis of asthma, and thus the use of imaging in asthma has historically been limited to excluding alternative diagnoses. However, significant advances continue to be made in novel imaging methodologies, which have been increasingly used to better understand respiratory impairment in asthma. As a disease primarily impacting the airways, asthma is best understood by imaging methods with the ability to elucidate airway impairment. Techniques such as computed tomography, magnetic resonance imaging with gaseous contrast agents, and positron emission tomography enable assessment of the small airways. Others, such as optical coherence tomography and endobronchial ultrasound enable high-resolution imaging of the large airways accessible to bronchoscopy. These imaging techniques are providing new insights in the pathophysiology and treatments of asthma and are poised to impact the clinical management of asthma.
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Pilot Quality-Assurance Study of a Third-Generation Batch-Mode Clinical-Scale Automated Xenon-129 Hyperpolarizer. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27041327. [PMID: 35209116 PMCID: PMC8879294 DOI: 10.3390/molecules27041327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 02/08/2022] [Accepted: 02/10/2022] [Indexed: 11/28/2022]
Abstract
We present a pilot quality assurance (QA) study of a clinical-scale, automated, third-generation (GEN-3) 129Xe hyperpolarizer employing batch-mode spin-exchange optical pumping (SEOP) with high-Xe densities (50% natural abundance Xe and 50% N2 in ~2.6 atm total pressure sourced from Nova Gas Technologies) and rapid temperature ramping enabled by an aluminum heating jacket surrounding the 0.5 L SEOP cell. 129Xe hyperpolarization was performed over the course of 700 gas loading cycles of the SEOP cell, simulating long-term hyperpolarized contrast agent production in a clinical lung imaging setting. High levels of 129Xe polarization (avg. %PXe = 51.0% with standard deviation σPXe = 3.0%) were recorded with fast 129Xe polarization build-up time constants (avg. Tb = 25.1 min with standard deviation σTb = 3.1 min) across the first 500 SEOP cell refills, using moderate temperatures of 75 °C. These results demonstrate a more than 2-fold increase in build-up rate relative to previously demonstrated results in a comparable QA study on a second-generation (GEN-2) 129Xe hyperpolarizer device, with only a minor reduction in maximum achievable %PXe and with greater consistency over a larger number of SEOP cell refill processes at a similar polarization lifetime duration (avg. T1 = 82.4 min, standard deviation σT1 = 10.8 min). Additionally, the effects of varying SEOP jacket temperatures, distribution of Rb metal, and preparation and operation of the fluid path are quantified in the context of device installation, performance optimization and maintenance to consistently produce high 129Xe polarization values, build-up rates (Tb as low as 6 min) and lifetimes over the course of a typical high-throughput 129Xe polarization SEOP cell life cycle. The results presented further demonstrate the significant potential for hyperpolarized 129Xe contrast agent in imaging and bio-sensing applications on a clinical scale.
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Comparison of Hyperpolarized 3He and 129Xe MR Imaging in Cystic Fibrosis Patients. Acad Radiol 2022; 29 Suppl 2:S82-S90. [PMID: 33487537 DOI: 10.1016/j.acra.2021.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/24/2020] [Accepted: 01/06/2021] [Indexed: 12/29/2022]
Abstract
PURPOSE In this study, we compared hyperpolarized 3He and 129Xe images from patients with cystic fibrosis using two commonly applied magnetic resonance sequences, standard gradient echo (GRE) and balanced steady-state free precession (TrueFISP) to quantify regional similarities and differences in signal distribution and defect analysis. MATERIALS AND METHODS Ten patients (7M/3F) with cystic fibrosis underwent hyperpolarized gas MR imaging with both 3He and 129Xe. Six had MRI with both GRE, and TrueFISP sequences and four patients had only GRE sequence but not TrueFISP. Ventilation defect percentages (VDPs) were calculated as lung voxels with <60% of the whole-lung hyperpolarized gas signal mean and was measured in all datasets. The voxel signal distributions of both 129Xe and 3He gases were visualized and compared using violin plots. VDPs of hyperpolarized 3 He and 129 Xe were compared in Bland-Altman plots; Pearson correlation coefficients were used to evaluate the relationships between inter-gas and inter-scan to assess the reproducibility. RESULTS A significant correlation was demonstrated between 129Xe VDP and 3He VDP for both GRE and TrueFISP sequences (ρ = 0.78, p<0.0004). The correlation between the GRE and TrueFISP VDP for 3He was ρ = 0.98 and was ρ = 0.91 for 129Xe. Overall, 129Xe (27.2±9.4) VDP was higher than 3He (24.3±6.9) VDP on average on cystic fibrosis patients. CONCLUSION In patients with cystic fibrosis, the selection of hyperpolarized 129Xe or 3He gas is most likely inconsequential when it comes to measure the overall lung function by VDP although 129Xe may be more sensitive to starker lung defects, particularly when using a TrueFISP sequence.
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Bronchopulmonary dysplasia from chest radiographs to magnetic resonance imaging and computed tomography: adding value. Pediatr Radiol 2022; 52:643-660. [PMID: 35122130 PMCID: PMC8921108 DOI: 10.1007/s00247-021-05250-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 09/13/2021] [Accepted: 11/25/2021] [Indexed: 12/31/2022]
Abstract
Bronchopulmonary dysplasia (BPD) is a common long-term complication of preterm birth. The chest radiograph appearance and survivability have evolved since the first description of BPD in 1967 because of improved ventilation and clinical strategies and the introduction of surfactant in the early 1990s. Contemporary imaging care is evolving with the recognition that comorbidities of tracheobronchomalacia and pulmonary hypertension have a great influence on outcomes and can be noninvasively evaluated with CT and MRI techniques, which provide a detailed evaluation of the lungs, trachea and to a lesser degree the heart. However, echocardiography remains the primary modality to evaluate and screen for pulmonary hypertension. This review is intended to highlight the important findings that chest radiograph, CT and MRI can contribute to precision diagnosis, phenotyping and prognosis resulting in optimal management and therapeutics.
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Magnetic shielding of parahydrogen hyperpolarization experiments for the masses. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2021; 59:1180-1186. [PMID: 33948988 PMCID: PMC8568740 DOI: 10.1002/mrc.5167] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 05/07/2023]
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Abstract
The use of magnetic resonance imaging (MRI) and spectroscopy (MRS) in the clinical setting enables the acquisition of valuable anatomical information in a rapid, non-invasive fashion. However, MRI applications for identifying disease-related biomarkers are limited due to low sensitivity at clinical magnetic field strengths. The development of hyperpolarized (hp) 129Xe MRI/MRS techniques as complements to traditional 1H-based imaging has been a burgeoning area of research over the past two decades. Pioneering experiments have shown that hp 129Xe can be encapsulated within host molecules to generate ultrasensitive biosensors. In particular, xenon has high affinity for cryptophanes, which are small organic cages that can be functionalized with affinity tags, fluorophores, solubilizing groups, and other moieties to identify biomedically relevant analytes. Cryptophane sensors designed for proteins, metal ions, nucleic acids, pH, and temperature have achieved nanomolar-to-femtomolar limits of detection via a combination of 129Xe hyperpolarization and chemical exchange saturation transfer (CEST) techniques. This review aims to summarize the development of cryptophane biosensors for 129Xe MRI applications, while highlighting innovative biosensor designs and the consequent enhancements in detection sensitivity, which will be invaluable in expanding the scope of 129Xe MRI. This review aims to summarize the development of cryptophane biosensors for 129Xe MRI applications, while highlighting innovative biosensor designs and the consequent enhancements in detection sensitivity, which will be invaluable in expanding the scope of 129Xe MRI.![]()
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Protocols for multi-site trials using hyperpolarized 129 Xe MRI for imaging of ventilation, alveolar-airspace size, and gas exchange: A position paper from the 129 Xe MRI clinical trials consortium. Magn Reson Med 2021; 86:2966-2986. [PMID: 34478584 DOI: 10.1002/mrm.28985] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 07/13/2021] [Accepted: 08/06/2021] [Indexed: 12/12/2022]
Abstract
Hyperpolarized (HP) 129 Xe MRI uniquely images pulmonary ventilation, gas exchange, and terminal airway morphology rapidly and safely, providing novel information not possible using conventional imaging modalities or pulmonary function tests. As such, there is mounting interest in expanding the use of biomarkers derived from HP 129 Xe MRI as outcome measures in multi-site clinical trials across a range of pulmonary disorders. Until recently, HP 129 Xe MRI techniques have been developed largely independently at a limited number of academic centers, without harmonizing acquisition strategies. To promote uniformity and adoption of HP 129 Xe MRI more widely in translational research, multi-site trials, and ultimately clinical practice, this position paper from the 129 Xe MRI Clinical Trials Consortium (https://cpir.cchmc.org/XeMRICTC) recommends standard protocols to harmonize methods for image acquisition in HP 129 Xe MRI. Recommendations are described for the most common HP gas MRI techniques-calibration, ventilation, alveolar-airspace size, and gas exchange-across MRI scanner manufacturers most used for this application. Moreover, recommendations are described for 129 Xe dose volumes and breath-hold standardization to further foster consistency of imaging studies. The intention is that sites with HP 129 Xe MRI capabilities can readily implement these methods to obtain consistent high-quality images that provide regional insight into lung structure and function. While this document represents consensus at a snapshot in time, a roadmap for technical developments is provided that will further increase image quality and efficiency. These standardized dosing and imaging protocols will facilitate the wider adoption of HP 129 Xe MRI for multi-site pulmonary research.
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Hyperpolarized 129 Xe multi-slice imaging of the human brain using a 3D gradient echo pulse sequence. Magn Reson Med 2021; 86:3175-3181. [PMID: 34272774 DOI: 10.1002/mrm.28932] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 06/10/2021] [Accepted: 06/30/2021] [Indexed: 12/14/2022]
Abstract
PURPOSE To demonstrate the possibility of performing multi-slice in-vivo human brain MRI using hyperpolarized (HP) xenon-129 (129 Xe) in two different orientations and to calculate the signal-to-noise ratio (SNR). METHODS Two healthy female participants were imaged during a single breath-hold of HP 129 Xe using a Philips Achieva 3.0T MRI scanner (Philips, Andover, MA). Each HP 129 Xe multi-slice brain image was acquired during separate HP 129 Xe breath-holds using 3D gradient echo (GRE) imaging. The acquisition started 10 s after the inhalation of 1 L of HP 129 Xe. Overall, four sagittal and three axial images were acquired (seven imaging sessions per participant). The SNR was calculated for each slice in both orientations. RESULTS The first ever HP 129 Xe multi-slice images of the brain were acquired in axial and sagittal orientations. The HP 129 Xe signal distribution correlated well with the gray matter distribution. The highest SNR values were close in the axial and sagittal orientations (19.46 ± 3.25 and 18.76 ± 4.94, respectively). Additionally, anatomical features, such as the ventricles, were observed in both orientations. CONCLUSION The possibility of using multi-slice HP 129 Xe human brain magnetic resonance imaging was demonstrated for the first time. HP 129 Xe multi-slice MRI can be implemented for brain imaging to improve current diagnostic methods.
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The effects of an initial depolarization pulse on dissolved phase hyperpolarized 129 Xe brain MRI. Magn Reson Med 2021; 86:3147-3155. [PMID: 34254356 DOI: 10.1002/mrm.28918] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 06/01/2021] [Accepted: 06/16/2021] [Indexed: 12/27/2022]
Abstract
PURPOSE To evaluate the effect of an initial 90° depolarization RF pulse on the dissolved-phase hyperpolarized (HP) xenon-129 (129 Xe) brain imaging and to compare the SNR variability of HP 129 Xe images acquired without an initial depolarization RF pulse to those following the initial depolarization pulse. METHODS Five cognitive normal healthy volunteers were imaged using a Philips Achieva 3.0T MRI scanner during a single breath-hold following inhalation of 1 L of HP 129 Xe. Each participant underwent six HP 129 Xe scans. Three scans were performed using conventional single-slice projection HP 129 Xe brain imaging, and the other three scans were performed using the HP 129 Xe time-of-flight imaging with an initial rectangular depolarization pulse. RESULTS Although the utilization of an initial depolarization results in the reduction of the mean image SNR, the presence of an initial depolarization RF pulse reduces the SNR variability of the HP 129 Xe brain image by a factor of 2.26. The highest SNR variability was observed from the posterior brain region, where the anterior region possessed the lower level of signal variability. CONCLUSION An initial 90° depolarization RF pulse, applied prior to the HP 129 Xe image acquisition, reduced the HP 129 Xe signal variability more than two times between the different breath-hold images.
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Reproducibility of Hyperpolarized 129Xe MRI Ventilation Defect Percent in Severe Asthma to Evaluate Clinical Trial Feasibility. Acad Radiol 2021; 28:817-826. [PMID: 32417033 DOI: 10.1016/j.acra.2020.04.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 04/07/2020] [Accepted: 04/15/2020] [Indexed: 02/06/2023]
Abstract
RATIONALE AND OBJECTIVES 129Xe MRI has been developed to noninvasively visualize and quantify the functional consequence of airway obstruction in asthma. Its widespread application requires evidence of intersite reproducibility and agreement. Our objective was to evaluate reproducibility and agreement of 129Xe ventilation MRI measurements in severe asthmatics at two sites. MATERIALS AND METHODS In seven adults with severe asthma, 129Xe ventilation MRI was acquired pre- and post-bronchodilator at two geographic sites within 24-hours. 129Xe MRI signal-to-noise ratio (SNR) was calculated and ventilation abnormalities were quantified as the whole-lung and slice-by-slice ventilation defect percent (VDP). Intraclass correlation coefficients (ICC) and Bland-Altman analysis were used to determine intersite 129Xe VDP reproducibility and agreement. RESULTS Whole-lung and slice-by-slice 129Xe VDP measured at both sites were correlated and reproducible (pre-bronchodilator: whole-lung ICC = 0.90, p = 0.005, slice-by-slice ICC = 0.78, p < 0.0001; post-bronchodilator: whole-lung ICC = 0.94, p < 0.0001, slice-by-slice ICC = 0.83, p < 0.0001) notwithstanding intersite differences in the 129Xe-dose-equivalent-volume (101 ± 15 mL site 1, 49 ± 6 mL site 2, p < 0.0001), gas-mixture (129Xe/4He site 1; 129Xe/N2 site 2) and SNR (40 ± 19 site 1, 23 ± 5 site 2, p = 0.02). Qualitative 129Xe gas distribution differences were observed between sites and slice-by-slice 129Xe VDP, but not whole-lung 129Xe VDP, was significantly lower at site 1 (pre-bronchodilator VDP: whole-lung bias = -3%, p > 0.99, slice-by-slice bias = -3%, p = 0.0001; post-bronchodilator VDP: whole-lung bias = -2%, p = 0.59, slice-by-slice-bias = -2%, p = 0.0003). CONCLUSION 129Xe MRI VDP at two different sites measured within 24-hours in the same severe asthmatics were correlated. Qualitative and quantitative intersite differences in 129Xe regional gas distribution and VDP point to site-specific variability that may be due to differences in gas-mixture composition or SNR.
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129Xe MRI as a measure of clinical disease severity for pediatric asthma. J Allergy Clin Immunol 2021; 147:2146-2153.e1. [PMID: 33227317 DOI: 10.1016/j.jaci.2020.11.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 11/06/2020] [Accepted: 11/11/2020] [Indexed: 01/20/2023]
Abstract
BACKGROUND Measurement of regional lung ventilation with hyperpolarized 129Xe magnetic resonance imaging (129Xe MRI) in pediatric asthma is poised to advance our understanding of disease mechanisms and pathophysiology in a disorder with diverse clinical phenotypes. 129Xe MRI has not been investigated in a pediatric asthma cohort. OBJECTIVE We hypothesized that 129Xe MRI is feasible and can demonstrate ventilation defects that relate to and predict clinical severity in a pediatric asthma cohort. METHODS Thirty-seven children (13 with severe asthma, 8 with mild/moderate asthma, 16 age-matched healthy controls) aged 6 to 17 years old were imaged with 129Xe MRI. Ventilation defect percentage (VDP) and image reader score were calculated and compared with clinical measures at baseline and at follow-up. RESULTS Children with asthma had higher VDP (P = .002) and number of defects per image slice (defects/slice) (P = .0001) than children without asthma. Children with clinically severe asthma had significantly higher VDP and number of defects/slice than healthy controls. Children with asthma who had a higher number of defects/slice had a higher rate of health care utilization (r = 0.48; P = .03) and oral corticosteroid use (r = 0.43; P = .05) at baseline. Receiver-operating characteristic analysis demonstrated that the VDP and number of defects/slice were predictive of increased health care utilization, asthma, and severe asthma. VDP correlated with FEV1 (r = -0.35; P = .04) and FEV1/forced vital capacity ratio (r = -0.41; P = .01). CONCLUSIONS 129Xe MRI correlates with asthma severity, health care utilization, and oral corticosteroid use. Because delineation of clinical severity is often difficult in children, 129Xe MRI may be an important biomarker for severity, with potential to identify children at higher risk for exacerbations and improve outcomes.
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Novel Thoracic MRI Approaches for the Assessment of Pulmonary Physiology and Inflammation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1304:123-145. [PMID: 34019267 DOI: 10.1007/978-3-030-68748-9_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Excessive pulmonary inflammation can lead to damage of lung tissue, airway remodelling and established structural lung disease. Novel therapeutics that specifically target inflammatory pathways are becoming increasingly common in clinical practice, but there is yet to be a similar stepwise change in pulmonary diagnostic tools. A variety of thoracic magnetic resonance imaging (MRI) tools are currently in development, which may soon fulfil this emerging clinical need for highly sensitive assessments of lung structure and function. Given conventional MRI techniques are poorly suited to lung imaging, alternate strategies have been developed, including the use of inhaled contrast agents, intravenous contrast and specialized lung MR sequences. In this chapter, we discuss technical challenges of performing MRI of the lungs and how they may be overcome. Key thoracic MRI modalities are reviewed, namely, hyperpolarized noble gas MRI, oxygen-enhanced MRI (OE-MRI), ultrashort echo time (UTE) MRI and dynamic contrast-enhanced (DCE) MRI. Finally, we consider potential clinical applications of these techniques including phenotyping of lung disease, evaluation of novel pulmonary therapeutic efficacy and longitudinal assessment of specific patient groups.
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Modern pulmonary imaging of bronchopulmonary dysplasia. J Perinatol 2021; 41:707-717. [PMID: 33547408 PMCID: PMC8561744 DOI: 10.1038/s41372-021-00929-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 11/05/2020] [Accepted: 01/15/2021] [Indexed: 01/30/2023]
Abstract
Bronchopulmonary dysplasia (BPD) is a complex and serious cardiopulmonary morbidity in infants who are born preterm. Despite advances in clinical care, BPD remains a significant source of morbidity and mortality, due in large part to the increased survival of extremely preterm infants. There are few strong early prognostic indicators of BPD or its later outcomes, and evidence for the usage and timing of various interventions is minimal. As a result, clinical management is often imprecise. In this review, we highlight cutting-edge methods and findings from recent pulmonary imaging research that have high translational value. Further, we discuss the potential role that various radiological modalities may play in early risk stratification for development of BPD and in guiding treatment strategies of BPD when employed in varying severities and time-points throughout the neonatal disease course.
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In vivo methods and applications of xenon-129 magnetic resonance. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2021; 122:42-62. [PMID: 33632417 PMCID: PMC7933823 DOI: 10.1016/j.pnmrs.2020.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 11/26/2020] [Accepted: 11/29/2020] [Indexed: 05/28/2023]
Abstract
Hyperpolarised gas lung MRI using xenon-129 can provide detailed 3D images of the ventilated lung airspaces, and can be applied to quantify lung microstructure and detailed aspects of lung function such as gas exchange. It is sensitive to functional and structural changes in early lung disease and can be used in longitudinal studies of disease progression and therapy response. The ability of 129Xe to dissolve into the blood stream and its chemical shift sensitivity to its local environment allow monitoring of gas exchange in the lungs, perfusion of the brain and kidneys, and blood oxygenation. This article reviews the methods and applications of in vivo129Xe MR in humans, with a focus on the physics of polarisation by optical pumping, radiofrequency coil and pulse sequence design, and the in vivo applications of 129Xe MRI and MRS to examine lung ventilation, microstructure and gas exchange, blood oxygenation, and perfusion of the brain and kidneys.
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Novel imaging techniques for cystic fibrosis lung disease. Pediatr Pulmonol 2021; 56 Suppl 1:S40-S54. [PMID: 32592531 PMCID: PMC7808406 DOI: 10.1002/ppul.24931] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 06/25/2020] [Indexed: 12/24/2022]
Abstract
With an increasing number of patients with cystic fibrosis (CF) receiving highly effective CFTR (cystic fibrosis transmembrane regulator protein) modulator therapy, particularly at a young age, there is an increasing need to identify imaging tools that can detect and regionally visualize mild CF lung disease and subtle changes in disease state. In this review, we discuss the latest developments in imaging modalities for both structural and functional imaging of the lung available to CF clinicians and researchers, from the widely available, clinically utilized imaging methods for assessing CF lung disease-chest radiography and computed tomography-to newer techniques poised to become the next phase of clinical tools-structural/functional proton and hyperpolarized gas magnetic resonance imaging (MRI). Finally, we provide a brief discussion of several newer lung imaging techniques that are currently available only in selected research settings, including chest tomosynthesis, and fluorinated gas MRI. We provide an update on the clinical and/or research status of each technique, with a focus on sensitivity, early disease detection, and possibilities for monitoring treatment efficacy.
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Damaged lung gas exchange function of discharged COVID-19 patients detected by hyperpolarized 129Xe MRI. SCIENCE ADVANCES 2021; 7:eabc8180. [PMID: 33219111 PMCID: PMC7775756 DOI: 10.1126/sciadv.abc8180] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Accepted: 11/02/2020] [Indexed: 05/28/2023]
Abstract
The recovery process of COVID-19 patients is unclear. Some recovered patients complain of continued shortness of breath. Vasculopathy has been reported in COVID-19, stressing the importance of probing pulmonary microstructure and function at the alveolar-capillary interface. While computed tomography (CT) detects structural abnormalities, little is known about the impact of disease on lung function. 129Xe magnetic resonance imaging (MRI) is a technique uniquely capable of assessing ventilation, microstructure, and gas exchange. Using 129Xe MRI, we found that COVID-19 patients show a higher rate of ventilation defects (5.9% versus 3.7%), unchanged microstructure, and longer gas-blood exchange time (43.5 ms versus 32.5 ms) compared with healthy individuals. These findings suggest that regional ventilation and alveolar airspace dimensions are relatively normal around the time of discharge, while gas-blood exchange function is diminished. This study establishes the feasibility of localized lung function measurements in COVID-19 patients and their potential usefulness as a supplement to structural imaging.
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Inhaled Gas Magnetic Resonance Imaging: Advances, Applications, Limitations, and New Frontiers. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00013-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Measuring pulmonary gas exchange using compartment-selective xenon-polarization transfer contrast (XTC) MRI. Magn Reson Med 2020; 85:2709-2722. [PMID: 33283943 DOI: 10.1002/mrm.28626] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 12/22/2022]
Abstract
PURPOSE To demonstrate the feasibility of generating red blood cell (RBC) and tissue/plasma (TP)-specific gas-phase (GP) depolarization maps using xenon-polarization transfer contrast (XTC) MR imaging. METHODS Imaging was performed in three healthy subjects, an asymptomatic smoker, and a chronic obstructive pulmonary disease (COPD) patient. Single-breath XTC data were acquired through a series of three GP images using a 2D multi-slice GRE during a 12 s breath-hold. A series of 8 ms Gaussian inversion pulses spaced 30 ms apart were applied in-between the images to quantify the exchange between the GP and dissolved-phase (DP) compartments. Inversion pulses were either centered on-resonance to generate contrast, or off-resonance to correct for other sources of signal loss. For an alternative scheme, inversions of both RBC and TP resonances were inserted in lieu of off-resonance pulses. Finally, this technique was extended to a multi-breath protocol consistent with tidal breathing, involving 30 consecutive acquisitions. RESULTS Inversion pulses shifted off-resonance by 20 ppm to mimic the distance between the RBC and TP resonances demonstrated selectivity, and initial GP depolarization maps illustrated stark magnitude and distribution differences between healthy and diseased subjects that were consistent with traditional approaches. CONCLUSION The proposed DP-compartment selective XTC MRI technique provides information on gas exchange between all three detectable states of xenon in the lungs and is sufficiently sensitive to indicate differences in lung function between the study subjects. Investigated extensions of this approach to imaging schemes that either minimize breath-hold duration or the overall number of breath-holds open avenues for future research to improve measurement accuracy and patient comfort.
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Parahydrogen-Induced Polarization of Diethyl Ether Anesthetic. Chemistry 2020; 26:13621-13626. [PMID: 32667687 PMCID: PMC7722203 DOI: 10.1002/chem.202002528] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 07/05/2020] [Indexed: 12/29/2022]
Abstract
The growing interest in magnetic resonance imaging (MRI) for assessing regional lung function relies on the use of nuclear spin hyperpolarized gas as a contrast agent. The long gas-phase lifetimes of hyperpolarized 129 Xe make this inhalable contrast agent acceptable for clinical research today despite limitations such as high cost, low throughput of production and challenges of 129 Xe imaging on clinical MRI scanners, which are normally equipped with proton detection only. We report on low-cost and high-throughput preparation of proton-hyperpolarized diethyl ether, which can be potentially employed for pulmonary imaging with a nontoxic, simple, and sensitive overall strategy using proton detection commonly available on all clinical MRI scanners. Diethyl ether is hyperpolarized by pairwise parahydrogen addition to vinyl ethyl ether and characterized by 1 H NMR spectroscopy. Proton polarization levels exceeding 8 % are achieved at near complete chemical conversion within seconds, causing the activation of radio amplification by stimulated emission radiation (RASER) throughout detection. Although gas-phase T1 relaxation of hyperpolarized diethyl ether (at partial pressure of 0.5 bar) is very efficient, with T1 of ca. 1.2 second, we demonstrate that, at low magnetic fields, the use of long-lived singlet states created via pairwise parahydrogen addition extends the relaxation decay by approximately threefold, paving the way to bioimaging applications and beyond.
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XeUS: A second-generation automated open-source batch-mode clinical-scale hyperpolarizer. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 319:106813. [PMID: 32932118 DOI: 10.1016/j.jmr.2020.106813] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 08/20/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
We present a second-generation open-source automated batch-mode 129Xe hyperpolarizer (XeUS GEN-2), designed for clinical-scale hyperpolarized (HP) 129Xe production via spin-exchange optical pumping (SEOP) in the regimes of high Xe density (0.66-2.5 atm partial pressure) and resonant photon flux (~170 W, Δλ = 0.154 nm FWHM), without the need for cryo-collection typically employed by continuous-flow hyperpolarizers. An Arduino micro-controller was used for hyperpolarizer operation. Processing open-source software was employed to program a custom graphical user interface (GUI), capable of remote automation. The Arduino Integrated Development Environment (IDE) was used to design a variety of customized automation sequences such as temperature ramping, NMR signal acquisition, and SEOP cell refilling for increased reliability. A polycarbonate 3D-printed oven equipped with a thermo-electric cooler/heater provides thermal stability for SEOP for both binary (Xe/N2) and ternary (4He-containing) SEOP cell gas mixtures. Quantitative studies of the 129Xe hyperpolarization process demonstrate that near-unity polarization can be achieved in a 0.5 L SEOP cell. For example, %PXe of 93.2 ± 2.9% is achieved at 0.66 atm Xe pressure with polarization build-up rate constant γSEOP = 0.040 ± 0.005 min-1, giving a max dose equivalent ≈ 0.11 L/h 100% hyperpolarized, 100% enriched 129Xe; %PXe of 72.6 ± 1.4% is achieved at 1.75 atm Xe pressure with γSEOP of 0.041 ± 0.001 min-1, yielding a corresponding max dose equivalent of 0.27 L/h. Quality assurance studies on this device have demonstrated the potential to refill SEOP cells hundreds of times without significant losses in performance, with average %PXe = 71.7%, (standard deviation σP = 1.52%) and mean polarization lifetime T1 = 90.5 min, (standard deviation σT = 10.3 min) over the first ~200 gas mixture refills, with sufficient performance maintained across a further ~700 refills. These findings highlight numerous technological developments and have significant translational relevance for efficient production of gaseous HP 129Xe contrast agents for use in clinical imaging and bio-sensing techniques.
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Cyst Ventilation Heterogeneity and Alveolar Airspace Dilation as Early Disease Markers in Lymphangioleiomyomatosis. Ann Am Thorac Soc 2020; 16:1008-1016. [PMID: 31038987 DOI: 10.1513/annalsats.201812-880oc] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Rationale: Lymphangioleiomyomatosis (LAM) is a rare disease associated with cystic destruction of the pulmonary parenchyma and chronic respiratory failure, and there are trials underway to determine if early intervention can prevent disease progression. An imaging technique that is sensitive to early regional disease would therefore be valuable for patient care and clinical trials.Objectives: We postulated that hyperpolarized 129Xe MRI would be sensitive to ventilation abnormalities and alveolar airspace dilation in patients with mild LAM disease and normal pulmonary function and that 129Xe MRI would reveal important features of cyst ventilation.Methods: 129Xe ventilation and diffusion-weighted MR images were acquired in 22 patients with LAM during two breath-holds of hyperpolarized 129Xe. 129Xe ventilation defect percentage (VDP; percentage of voxels <60% of the mean whole-lung 129Xe MRI signal) and apparent diffusion coefficient (ADC), a measure of alveolar airspace size, were quantified and compared with pulmonary function test parameters with Spearman statistics. Sixteen patients with LAM had a recent, clinical chest computed tomography (CT) scan available, and cyst ventilation was assessed by thresholding cysts on the CT images and registration to the 129Xe ventilation images.Results: Ventilation deficits were observed in all patients with LAM, including those with normal pulmonary function and few cysts, and the mean VDP was 19.2% (95% confidence interval [CI], 14.8-23.5%). 129Xe VDP was strongly correlated with forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio (r = -0.51, P = 0.02) and diffusing capacity of the lung for carbon monoxide (DlCO) (r = -0.60, P = 0.009) but not with FEV1 (r = -0.33, P = 0.13), likely because of the sensitivity of 129Xe MRI to mild LAM disease in patients with normal FEV1. The mean ADC was 0.048 cm2/s (95% CI, 0.042-0.053 cm2/s). In many cases, ADC was elevated relative to previously reported values in adults, and ADC was correlated with FEV1, FEV1/FVC ratio, and DlCO (P ≤ 0.02 for all). Co-registered 129Xe MRI and CT imaging revealed considerable ventilation heterogeneity within individual patients with LAM and across patients with similarly sized cysts.Conclusions: 129Xe MRI provides a means to assess the complex regional ventilation and alveolar airspace size changes of LAM with high sensitivity and may be a clinically useful future tool for screening, managing patients, and measuring treatment efficacy.
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Pilot multi-site quality assurance study of batch-mode clinical-scale automated xenon-129 hyperpolarizers. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 316:106755. [PMID: 32512397 DOI: 10.1016/j.jmr.2020.106755] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/21/2020] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
We present a pilot quality assurance (QA) study of spin-exchange optical pumping (SEOP) performed on two nearly identical second-generation (GEN-2) automated batch-mode clinical-scale 129Xe hyperpolarizers, each utilizing a convective forced air oven, high-power (~170 W) continuous pump laser irradiation, and xenon-rich gas mixtures (~1.30 atm partial pressure). In one study, the repeatability of SEOP in a 1000 Torr Xe/900 Torr N2/100 Torr 4He (2000 Torr total pressure) gas mixture is evaluated over the course of ~700 gas loading cycles, with negligible decrease in performance during the first ~200 cycles, and with high 129Xe polarization levels (avg. %PXe = 71.7% with standard deviation σPXe = 1.5%), build-up rates (avg. γSEOP = 0.019 min-1 with standard deviation σγ = 0.003 min-1) and polarization lifetimes (avg. T1 = 90.5 min with standard deviation σT = 10.3 min) reported at moderate oven temperature of ~70 °C. Although the SEOP cell in this study exhibited a detectable performance decrease after 400 cycles, the cell continued to produce potentially useable HP 129Xe with %PXe = 42.3 ± 0.6% even after nearly 700 refill cycles. The possibility of "regenerating" "dormant" (i.e., not used for an extended period of time) SEOP cells using repeated temperature cycling methods to recover %PXe is also demonstrated. The quality and consistency of results show significant promise for translation to clinical-scale production of hyperpolarized 129Xe contrast agents for imaging and bio-sensing applications.
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Helium-rich mixtures for improved batch-mode clinical-scale spin-exchange optical pumping of Xenon-129. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 315:106739. [PMID: 32408239 DOI: 10.1016/j.jmr.2020.106739] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 04/24/2020] [Indexed: 06/11/2023]
Abstract
We present studies of spin-exchange optical pumping (SEOP) using ternary xenon-nitrogen-helium gas mixtures at high xenon partial pressures (up to 1330 Torr partial pressure at loading, out of 2660 Torr total pressure) in a 500-mL volume SEOP cell, using two automated batch-mode clinical-scale 129Xe hyperpolarizers operating under continuous high-power (~170 W) pump laser irradiation. In this pilot study, we explore SEOP in gas mixtures with up to 45% 4He content under a wide range of experimental conditions. When an aluminum jacket cooling/heating design was employed (GEN-3 hyperpolarizer), 129Xe polarization (%PXe) of 55.9 ± 0.9% was observed with mono-exponential build-up rate γSEOP of 0.049 ± 0.001 min-1 for the 4He-rich mixture (1000 Torr Xe/900 Torr He, 100 Torr N2), compared to %PXe of 49.3 ± 3.3% at γSEOP of 0.035 ± 0.004 min-1 for the N2-rich gas mixture (1000 Torr Xe/100 Torr He, 900 Torr N2). When forced-air cooling/heating was used (GEN-2 hyperpolarizer), %PXe of 83.9 ± 2.7% was observed at γSEOP of 0.045 ± 0.005 min-1 for the 4He-rich mixture (1000 Torr Xe/900 Torr He, 100 Torr N2), compared to %PXe of 73.5 ± 1.3% at γSEOP of 0.028 ± 0.001 min-1 for the N2-rich gas mixture (1000 Torr Xe and 1000 Torr N2). Additionally, %PXe of 72.6 ± 1.4% was observed at a build-up rate γSEOP of 0.041 ± 0.003 min-1 for a super-high-density 4He-rich mixture (1330 Torr Xe/1200 Torr 4He/130 Torr N2), compared to %PXe = 56.6 ± 1.3% at a build-up rate of γSEOP of 0.034 ± 0.002 min-1 for an N2-rich mixture (1330 Torr Xe/1330 Torr N2) using forced air cooling/heating. The observed SEOP hyperpolarization performance under these conditions corresponds to %PXe improvement by a factor of 1.14 ± 0.04 at 1000 Torr Xe density and by up to a factor of 1.28 ± 0.04 at 1330 Torr Xe density at improved SEOP build-up rates by factors of 1.61 ± 0.18 and 1.21 ± 0.11 respectively. Record %PXe levels have been obtained here: 83.9 ± 2.7% at 1000 Torr Xe partial pressure and 72.6 ± 1.4% at 1330 Torr Xe partial pressure. In addition to improved thermal stability for SEOP, the use of 4He-rich gas mixtures also reduces the overall density of produced inhalable HP contrast agents; this property may be desirable for HP 129Xe inhalation by human subjects in clinical settings-especially in populations with heavily impaired lung function. The described approach should enjoy ready application in the production of inhalable 129Xe contrast agent with near-unity 129Xe nuclear spin polarization.
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Transverse relaxation rates of pulmonary dissolved-phase Hyperpolarized 129 Xe as a biomarker of lung injury in idiopathic pulmonary fibrosis. Magn Reson Med 2020; 84:1857-1867. [PMID: 32162357 DOI: 10.1002/mrm.28246] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 02/12/2020] [Accepted: 02/12/2020] [Indexed: 12/24/2022]
Abstract
PURPOSE The MR properties (chemical shifts and R 2 ∗ decay rates) of dissolved-phase hyperpolarized (HP) 129 Xe are confounded by the large magnetic field inhomogeneity present in the lung. This work improves measurements of these properties using a model-based image reconstruction to characterize the R 2 ∗ decay rates of dissolved-phase HP 129 Xe in healthy subjects and patients with idiopathic pulmonary fibrosis (IPF). METHODS Whole-lung MRS and 3D radial MRI with four gradient echoes were performed after inhalation of HP 129 Xe in healthy subjects and patients with IPF. A model-based image reconstruction formulated as a regularized optimization problem was solved iteratively to measure regional signal intensity in the gas, barrier, and red blood cell (RBC) compartments, while simultaneously measuring their chemical shifts and R 2 ∗ decay rates. RESULTS The estimation of spectral properties reduced artifacts in images of HP 129 Xe in the gas, barrier, and RBC compartments and improved image SNR by over 20%. R 2 ∗ decay rates of the RBC and barrier compartments were lower in patients with IPF compared to healthy subjects (P < 0.001 and P = 0.005, respectively) and correlated to DLCO (R = 0.71 and 0.64, respectively). Chemical shift of the RBC component measured with whole-lung spectroscopy was significantly different between IPF and normal subjects (P = 0.022). CONCLUSION Estimates for R 2 ∗ in both barrier and RBC dissolved-phase HP 129 Xe compartments using a regional signal model improved image quality for dissolved-phase images and provided additional biomarkers of lung injury in IPF.
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Batch-Mode Clinical-Scale Optical Hyperpolarization of Xenon-129 Using an Aluminum Jacket with Rapid Temperature Ramping. Anal Chem 2020; 92:4309-4316. [PMID: 32073251 DOI: 10.1021/acs.analchem.9b05051] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We present spin-exchange optical pumping (SEOP) using a third-generation (GEN-3) automated batch-mode clinical-scale 129Xe hyperpolarizer utilizing continuous high-power (∼170 W) pump laser irradiation and a novel aluminum jacket design for rapid temperature ramping of xenon-rich gas mixtures (up to 2 atm partial pressure). The aluminum jacket design is capable of heating SEOP cells from ambient temperature (typically 25 °C) to 70 °C (temperature of the SEOP process) in 4 min, and perform cooling of the cell to the temperature at which the hyperpolarized gas mixture can be released from the hyperpolarizer (with negligible amounts of Rb metal leaving the cell) in approximately 4 min, substantially faster (by a factor of 6) than previous hyperpolarizer designs relying on air heat exchange. These reductions in temperature cycling time will likely be highly advantageous for the overall increase of production rates of batch-mode (i.e., stopped-flow) 129Xe hyperpolarizers, which is particularly beneficial for clinical applications. The additional advantage of the presented design is significantly improved thermal management of the SEOP cell. Accompanying the heating jacket design and performance, we also evaluate the repeatability of SEOP experiments conducted using this new architecture, and present typically achievable hyperpolarization levels exceeding 40% at exponential build-up rates on the order of 0.1 min-1.
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Delayed ventilation assessment using fast dynamic hyperpolarised Xenon-129 magnetic resonance imaging. Eur Radiol 2020; 30:1145-1155. [PMID: 31485836 PMCID: PMC6957546 DOI: 10.1007/s00330-019-06415-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/09/2019] [Accepted: 08/07/2019] [Indexed: 12/18/2022]
Abstract
OBJECTIVES To investigate the use of a fast dynamic hyperpolarised 129Xe ventilation magnetic resonance imaging (DXeV-MRI) method for detecting and quantifying delayed ventilation in patients with chronic obstructive pulmonary disease (COPD). METHODS Three male participants (age range 31-43) with healthy lungs and 15 patients (M/F = 12:3, age range = 48-73) with COPD (stages II-IV) underwent spirometry tests, quantitative chest computed tomography (QCT), and DXeV-MRI at 1.5-Tesla. Regional delayed ventilation was captured by measuring the temporal signal change in each lung region of interest (ROI) in comparison to that in the trachea. In addition to its qualitative assessment through visual inspection by a clinical radiologist, delayed ventilation was quantitatively captured by calculating a covariance measurement of the lung ROI and trachea signals, and quantified using both the time delay, and the difference between the integrated areas covered by the signal-time curves of the two signals. RESULTS Regional temporal ventilation, consistent with the expected physiological changes across a free breathing cycle, was demonstrated with DXeV-MRI in all patients. Delayed ventilation was observed in 13 of the 15 COPD patients and involved variable lung ROIs. This was in contrast to the control group, where no delayed ventilation was demonstrated (p = 0.0173). CONCLUSIONS DXeV-MRI offers a non-invasive way of detecting and quantifying delayed ventilation in patients with COPD, and provides physiological information on regional pulmonary function during a full breathing cycle. KEY POINTS • Dynamic xenon MRI allows for the non-invasive detection and measurement of delayed ventilation in COPD patients. • Dynamic xenon MRI during a free breathing cycle can provide unique information about pulmonary physiology and pulmonary disease pathophysiology. • With further validation, dynamic xenon MRI could offer a non-invasive way of measuring collateral ventilation which can then be used to guide lung volume reduction therapy (LVRT) for certain COPD patients.
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Alveolar Airspace Size in Healthy and Diseased Infant Lungs Measured via Hyperpolarized 3He Gas Diffusion Magnetic Resonance Imaging. Neonatology 2020; 117:704-712. [PMID: 33176330 PMCID: PMC7878286 DOI: 10.1159/000511084] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 08/22/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Alveolar development and lung parenchymal simplification are not well characterized in vivo in neonatal patients with respiratory morbidities, such as bronchopulmonary dysplasia (BPD). Hyperpolarized (HP) gas diffusion magnetic resonance imaging (MRI) is a sensitive, safe, nonionizing, and noninvasive biomarker for measuring airspace size in vivo but has not yet been implemented in young infants. OBJECTIVE This work quantified alveolar airspace size via HP gas diffusion MRI in healthy and diseased explanted infant lung specimens, with comparison to histological morphometry. METHODS Lung specimens from 8 infants were obtained: 7 healthy left upper lobes (0-16 months, post-autopsy) and 1 left lung with filamin-A mutation, closely representing BPD lung disease (11 months, post-transplantation). Specimens were imaged using HP 3He diffusion MRI to generate apparent diffusion coefficients (ADCs) as biomarkers of alveolar airspace size, with comparison to mean linear intercept (Lm) via quantitative histology. RESULTS Mean ADC and Lm were significantly increased throughout the diseased specimen (ADC = 0.26 ± 0.06 cm2/s, Lm = 587 ± 212 µm) compared with healthy specimens (ADC = 0.14 ± 0.03 cm2/s, Lm = 133 ± 37 µm; p < 1 × 10-7); increased values reflect enlarged airspaces. Mean ADCs in healthy specimens were significantly correlated to Lm (r = 0.69, p = 0.041). CONCLUSIONS HP gas diffusion MRI is sensitive to healthy and diseased regional alveolar airspace size in infant lungs, with good comparison to quantitative histology in ex vivo specimens. This work demonstrates the translational potential of gas MRI techniques for in vivo assessment of normal and abnormal alveolar development in neonates with pulmonary disease.
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Improved pulmonary 129 Xe ventilation imaging via 3D-spiral UTE MRI. Magn Reson Med 2019; 84:312-320. [PMID: 31788858 DOI: 10.1002/mrm.28114] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/13/2019] [Accepted: 11/15/2019] [Indexed: 02/03/2023]
Abstract
PURPOSE Hyperpolarized 129 Xe MRI characterizes regional lung ventilation in a variety of disease populations, with high sensitivity to airway obstruction in early disease. However, ventilation images are usually limited to a single breath-hold and most-often acquired using gradient-recalled echo sequences with thick slices (~10-15 mm), which increases partial-volume effects, limits ability to observe small defects, and suffers from imperfect slice selection. We demonstrate higher-resolution ventilation images, in shorter breath-holds, using FLORET (Fermat Looped ORthogonally Encoded Trajectories), a center-out 3D-spiral UTE sequence. METHODS In vivo human adult (N = 4; 2 healthy, 2 with cystic fibrosis) 129 Xe images were acquired using 2D gradient-recalled echo, 3D radial, and FLORET. Each sequence was acquired at its highest possible resolution within a 16-second breath-hold with a minimum voxel dimension of 3 mm. Images were compared using 129 Xe ventilation defect percentage, SNR, similarity coefficients, and vasculature cross-sections. RESULTS The FLORET sequence obtained relative normalized SNR, 40% greater than 2D gradient-recalled echo (P = .012) and 26% greater than 3D radial (P = .067). Moreover, the FLORET images were acquired with 3-fold-higher nominal resolution in a 15% shorter breath-hold. Finally, vasculature was less prominent in FLORET, likely due to diminished susceptibility-induced dephasing at shorter TEs afforded by UTE sequences. CONCLUSION The FLORET sequence yields higher SNR for a given resolution with a shorter breath-hold than traditional ventilation imaging techniques. This sequence more accurately measures ventilation abnormalities and enables reduced scan times in patients with poor compliance and severe lung disease.
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Assessing the feasibility of hyperpolarized
129
Xe multiple‐breath washout MRI in pediatric cystic fibrosis. Magn Reson Med 2019; 84:304-311. [DOI: 10.1002/mrm.28099] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 10/11/2019] [Accepted: 11/05/2019] [Indexed: 12/16/2022]
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Accelerated 129 Xe MRI morphometry of terminal airspace enlargement: Feasibility in volunteers and those with alpha-1 antitrypsin deficiency. Magn Reson Med 2019; 84:416-426. [PMID: 31765497 DOI: 10.1002/mrm.28091] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 12/21/2022]
Abstract
PURPOSE Multi-b diffusion-weighted hyperpolarized inhaled-gas MRI provides imaging biomarkers of terminal airspace enlargement including ADC and mean linear intercept (Lm ), but clinical translation has been limited because image acquisition requires relatively long or multiple breath-holds that are not well-tolerated by patients. Therefore, we aimed to accelerate single breath-hold 3D multi-b diffusion-weighted 129 Xe MRI, using k-space undersampling in imaging direction using a different undersampling pattern for different b-values combined with the stretched exponential model to generate maps of ventilation, apparent transverse relaxation time constant ( T 2 ∗ ), ADC, and Lm values in a single, short breath-hold; accelerated and non-accelerated measurements were directly compared. METHODS We evaluated multi-b (0, 12, 20, 30, and 45.5 s/cm2 ) diffusion-weighted 129 Xe T 2 ∗ /ADC/morphometry estimates using acceleration factor (AF = 1 and 7) and multi-breath sampling in 3 volunteers (HV), and 6 participants with alpha-1 antitrypsin deficiency (AATD). RESULTS For the HV subgroup, mean differences of 5%, 2%, and 8% were observed between fully sampled and undersampled k-space for ADC, Lm , and T 2 ∗ values, respectively. For the AATD subgroup, mean differences were 9%, 6%, and 12% between fully sampled and undersampled k-space for ADC, Lm and T 2 ∗ values, respectively. Although mean differences of 1% and 4.5% were observed between accelerated and multi-breath sampled ADC and Lm values, respectively, mean ADC/Lm estimates were not significantly different from corresponding mean ADCM /Lm M or mean ADCA /Lm A estimates (all P > 0.60 , A = undersampled and M = multi-breath sampled). CONCLUSIONS Accelerated multi-b diffusion-weighted 129 Xe MRI is feasible at AF = 7 for generating pulmonary ADC and Lm in AATD and normal lung.
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Pulmonary xenon-129 MRI: new opportunities to unravel enigmas in respiratory medicine. Eur Respir J 2019; 55:13993003.01987-2019. [PMID: 31699844 DOI: 10.1183/13993003.01987-2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 10/24/2019] [Indexed: 11/05/2022]
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Quantification of Ventilation and Gas Uptake in Free-Breathing Mice With Hyperpolarized 129Xe MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:2081-2091. [PMID: 30990426 PMCID: PMC7268199 DOI: 10.1109/tmi.2019.2911293] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Hyperpolarized 129Xe magnetic resonance imaging is a powerful modality capable of assessing lung structure and function. While it has shown promise as a clinical tool for the longitudinal assessment of lung function, its utility as an investigative tool for animal models of pulmonary diseases is limited by the necessity of invasive intubation and mechanical ventilation procedures. In this paper, we overcame this limitation by developing a gas delivery system and implementing a set of imaging schemes to acquire high-resolution gas- and dissolved-phase images in free-breathing mice. Gradient echo pulse sequences were used to acquire both high- and low-resolution gas-phase images, and regional fractional ventilation was quantified by comparing signal buildup among low-resolution gas-phase images acquired at two flip-angles. Dissolved-phase images were acquired using both ultra-short echo time and chemical shift imaging sequences with discrete sets of flip-angle/repetition time combinations to visualize gas uptake and distribution throughout the body. Spectral features distinct to various anatomical regions were identified in images acquired using the latter sequence and were used for the quantification of gas arrival times for respective compartments.
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