For dyspneic patients 3 months after discharge from the hospital for COVID-19, hyperpolarized 129 Xe MRI showed abnormalities due to gas transfer limitation in the lungs. Key Results In nine patients evaluated at 3 months post hospital discharge for COVID-19, hyperpolarized 129 Xe MRI identifies regional RBC:TP abnormalities, in comparison to healthy controls, (0.3 ± 0.1 versus 0.5 ± 0.1, respectively, p = 0.001, effect size = 1.36) despite structurally normal/near normal lungs on CT post COVID-19 pneumonia. Hyperpolarized 129 Xe MRI gas transfer abnormalities are present post COVID-19 pneumonia even when patient clinical measurements such as D-dimer, hemoglobin and lung function tests are within normal range.

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Purpose:To compare lobar ventilation and apparent diffusion coefficient (ADC) values obtained with hyperpolarized xenon 129 ( 129 Xe) magnetic resonance (MR) imaging to quantitative computed tomography (CT) metrics on a lobar basis and pulmonary function test (PFT) results on a wholelung basis in patients with chronic obstructive pulmonary disease (COPD). Materials andMethods:The study was approved by the National Research Ethics Service Committee; written informed consent was obtained from all patients. Results:Percentage ventilated volume and average ADC at lobar 129 Xe MR imaging showed correlation with percentage emphysema at lobar quantitative CT (r = 20.32, P , .001 and r = 0.75, P , .0001, respectively). The average ADC at whole-lung 129 Xe MR imaging showed moderate correlation with PFT results (percentage predicted transfer factor of the lung for carbon monoxide [Tlco]: r = 20.61, P , .005) and percentage predicted functional residual capacity (r = 0.47, P , .05). Whole-lung quantitative CT percentage emphysema also showed statistically significant correlation with percentage predicted Tlco (r = 20.65, P , .005). Conclusion:Lobar ventilation and ADC values obtained from hyperpolarized 129Xe MR imaging demonstrated correlation with quantitative CT percentage emphysema on a lobar basis and with PFT results on a whole-lung basis.q RSNA, 2016

Purpose To derive lobar ventilation in patients with chronic obstructive pulmonary disease (COPD) using a rapid time-series hyperpolarized xenon-129 (HPX) magnetic resonance imaging (MRI) technique and compare this to ventilation/perfusion single-photon emission computed tomography (V/Q-SPECT), correlating the results with high-resolution computed tomography (CT) and pulmonary function tests (PFTs). Materials and methods Twelve COPD subjects (GOLD stages I–IV) participated in this study and underwent HPX-MRI, V/Q-SPECT/CT, high-resolution CT, and PFTs. HPX-MRI was performed using a novel time-series spiral k-space sampling approach. Relative percentage ventilations were calculated for individual lobe for comparison to the relative SPECT lobar ventilation and perfusion. The absolute HPX-MRI percentage ventilation in each lobe was compared to the absolute CT percentage emphysema score calculated using a signal threshold method. Pearson’s correlation and linear regression tests were performed to compare each imaging modality. Results Strong correlations were found between the relative lobar percentage ventilation with HPX-MRI and percentage ventilation SPECT ( r = 0.644; p < 0.001) and percentage perfusion SPECT ( r = 0.767; p < 0.001). The absolute CT percentage emphysema and HPX percentage ventilation correlation was also statistically significant ( r = 0.695, p < 0.001). The whole lung HPX percentage ventilation correlated with the PFT measurements (FEV 1 with r = − 0.886, p < 0.001*, and FEV 1 /FVC with r = − 0.861, p < 0.001*) better than the whole lung CT percentage emphysema score (FEV 1 with r = − 0.635, p = 0.027; and FEV 1 /FVC with r = − 0.652, p = 0.021). Conclusion Lobar ventilation with HPX-MRI showed a strong correlation with lobar ventilation and perfusion measurements derived from SPECT/CT, and is better than the emphysema score obtained with high-resolution CT. Key Points • The ventilation hyperpolarized xenon-129 MRI correlates well with ventilation and perfusion with SPECT/CT with the advantage of higher temporal and spatial resolution. • The hyperpolarized xenon-129 MRI correlates with the PFT measurements better than the high-resolution CT with the advantage of avoiding the use of ionizing radiation. Electronic supplementary material The online version of this article (10.1007/s00330-018-5888-y) contains supplementary material,...

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Purpose To perform magnetic resonance imaging (MRI), human lung imaging, and quantification of the gas-transfer dynamics of hyperpolarized xenon-129 (HPX) from the alveoli into the blood plasma. Materials and methods HPX MRI with iterative decomposition of water and fat with echo asymmetry and least-square estimation (IDEAL) approach were used with multi-interleaved spiral k-space sampling to obtain HPX gas and dissolved phase images. IDEAL time-series images were then obtained from ten subjects including six normal subjects and four patients with pulmonary emphysema to test the feasibility of the proposed technique for capturing xenon-129 gas-transfer dynamics (XGTD). The dynamics of xenon gas diffusion over the entire lung was also investigated by measuring the signal intensity variations between three regions of interest, including the left and right lungs and the heart using Welch’s t test. Results The technique enabled the acquisition of HPX gas and dissolved phase compartment images in a single breath-hold interval of 8 s. The y -intersect of the XGTD curves were also found to be statistically lower in the patients with lung emphysema than in the healthy group ( p < 0.05). Conclusion This time-series IDEAL technique enables the visualization and quantification of inhaled xenon from the alveoli to the left ventricle with a clinical gradient strength magnet during a single breath-hold, in healthy and diseased lungs. Key Points • The proposed hyperpolarized xenon-129 gas and dissolved magnetic resonance imaging technique can provide regional and temporal measurements of xenon-129 gas-transfer dynamics. • Quantitative measurement of xenon-129 gas-transfer dynamics from the alveolar to the heart was demonstrated in normal subjects and pulmonary emphysema. • Comparison of gas-transfer dynamics in normal subjects and pulmonary emphysema showed that the proposed technique appears sensitive to changes affecting the alveoli, pulmonary interstitium, and capillaries. Electronic supplementary material The online version of this article (10.1007/s00330-018-5853-9) contains supplementary material, which is available to authorized users.

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BackgroundLong-COVID is an umbrella term used to describe ongoing symptoms following COVID-19 infection after four weeks. Symptoms are wide-ranging but breathlessness is one of the most common and can persist for months after the initial infection. Investigations including Computed Tomography (CT), and physiological measurements (lung function tests) are usually unremarkable. The mechanisms driving breathlessness remain unclear, and this may be hindering the development of effective treatments.MethodsEleven non-hospitalised Long-COVID (NHLC, 4 male), 12 post-hospitalised COVID-19 (PHC, 10 male) patients were recruited from a Post-COVID Assessment clinic, and thirteen healthy controls (6 female) were recruited to undergo Hyperpolarized Xenon Magnetic Resonance Imaging (Hp-XeMRI). NHLC and PHC participants underwent contemporaneous CT, Hp-XeMRI, lung function tests, 1-minute sit-to-stand test and breathlessness questionnaires. Statistical analysis included group and pair-wise comparisons between patients and controls, and correlations between patient clinical and imaging data.ResultsNHLC and PHC patients were 287 ± 79 [range 190-437] and 149 ± 68 [range 68-269] days from infection, respectively. All NHLC patients had normal CT scans, and the PHC had normal or near normal CT scans (0.3/25 ± 0.6 [range 0-2] and 7/25 ± 5 [range 4-8], respectively). There was a significant difference in TLco (%) between NHLC and PHC patients (76 ± 8 % vs 86 ± 8%, respectively, p = 0.04) but no differences in other measurements of lung function. There were significant differences in RBC:TP mean between volunteers (0.45 ± 0.07, range [0.33-0.55]) and PHC (0.31 ± 0.11, [range 0.16-0.37]) and NHLC (0.35 ± 0.09, [range 0.26-0.58]) patients, but not between NHLC and PHC (p = 0.26).ConclusionThere are RBC:TP abnormalities in NHLC and PHC patients, with NHLC patients also demonstrating lower TLco than PHC patients despite their having normal CT scans. These abnormalities are present many months after the initial infection.Summary statementHyperpolarized Xenon MRI and TLco demonstrate significantly impaired gas transfer in non-hospitalised long-COVID patients when all other investigations are normal.Key resultsThere are significant differences in RBC:TP mean between healthy controls and PHC/NHLC patients (0.45 ± 0.07, range [0.33-0.55], 0.31 ± 0.11, [range 0.16-0.37], 0.35 ± 0.09, [range 0.26-0.58], respectively, p < 0.05 after correction for multiple comparisons) indicating a change in lung compartment volumes between groups.There was a significant difference in TLco (%) between NHLC and PHC patients (76 ± 8 % vs 86 ± 8%, respectively, p = 0.04), despite normal or near normal FEV (%) (100 ± 13% [range 72-123%] and 88 ± 21% [range 62-113%], p>0.05.There were significant differences in CT abnormalities between NHLC and PHC patients (0.3/25 ± 0.6 [range 0-2] and 7/25 ± 5 [range 4-8], respectively) despite similarly impaired RBC:TP.