From the Department of Physiology, Anatomy, and Genetics (J.T.G.), Oxford Centre for Clinical MR Research (J.T.G., B.R.), Medical Research Council Human Immunology Unit (L.H.), and Department of Oncology (F.G.), University of Oxford, Old Road, Headington, Oxford 0X3 7DQ, England; Department of Radiology, The Churchill Hospital (J.T.G., M.C., G.A., A.M., V.M., F.G.), and Oxford Interstitial Lung Disease Service (E.F., L.H.), Oxford National Health Service Foundation Trust, Oxford, England; Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, England (J.T.G.); and Polarised Lung and Respiratory Imaging Sheffield, Department of Infection Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, England (G.J.C., J.M.W.).
Radiology. 2021 Oct;301(1):E353-E360. doi: 10.1148/radiol.2021210033. Epub 2021 May 25.
Background SARS-CoV-2 targets angiotensin-converting enzyme 2-expressing cells in the respiratory tract. There are reports of breathlessness in patients many months after infection. Purpose To determine whether hyperpolarized xenon 129 MRI (XeMRI) imaging could be used to identify the possible cause of breathlessness in patients at 3 months after hospital discharge following COVID-19 infection. Materials and Methods This prospective study was undertaken between August and December of 2020, with patients and healthy control volunteers being enrolled. All patients underwent lung function tests; ventilation and dissolved-phase XeMRI, with the mean red blood cell (RBC) to tissue or plasma (TP) ratio being calculated; and a low-dose chest CT, with scans being scored for the degree of abnormalities after COVID-19. Healthy control volunteers underwent XeMRI. The intraclass correlation coefficient was calculated for volunteer and patient scans to assess repeatability. A Wilcoxon rank sum test and Cohen effect size calculation were performed to assess differences in the RBC/TP ratio between patients and control volunteers. Results Nine patients (mean age, 57 years ± 7 [standard deviation]; six male patients) and five volunteers (mean age, 29 years ± 3; five female volunteers) were enrolled. The mean time from hospital discharge for patients was 169 days (range, 116-254 days). There was a difference in the RBC/TP ratio between patients and control volunteers (0.3 ± 0.1 vs 0.5 ± 0.1, respectively; = .001; effect size, 1.36). There was significant difference between the RBC and gas phase spectral full width at half maximum between volunteers and patients (median ± range, 567 ± 1 vs 507 ± 81 [ = .002] and 104 ± 2 vs 122 ± 17 [ = .004], respectively). Results were reproducible, with intraclass correlation coefficients of 0.82 and 0.88 being demonstrated for patients and volunteers, respectively. Participants had normal or nearly normal CT scans (mean, seven of 25; range, zero of 25 to 10 of 25). Conclusion Hyperpolarized xenon 129 MRI results showed alveolar capillary diffusion limitation in all nine patients after COVID-19 pneumonia, despite normal or nearly normal results at CT. © RSNA, 2021 See also the editorial by Dietrich in this issue.
背景 SARS-CoV-2 靶向呼吸道中表达血管紧张素转换酶 2 的细胞。有报道称，感染后数月的患者会出现呼吸困难。目的 确定在 COVID-19 感染后出院 3 个月时，超极化氙 129 MRI（XeMRI）成像是否可用于识别呼吸困难的可能原因。材料与方法 本前瞻性研究于 2020 年 8 月至 12 月进行，招募了患者和健康对照志愿者。所有患者均进行了肺功能检查；进行通气和溶解相 XeMRI，计算平均红细胞（RBC）与组织或血浆（TP）比；进行低剂量胸部 CT，根据 COVID-19 后异常程度对扫描进行评分。健康对照志愿者进行 XeMRI。计算志愿者和患者扫描的组内相关系数，以评估重复性。采用 Wilcoxon 秩和检验和 Cohen 效应量计算，比较患者和对照组志愿者 RBC/TP 比值的差异。结果 共纳入 9 例患者（平均年龄 57 岁±7[标准差]；6 例男性患者）和 5 例志愿者（平均年龄 29 岁±3；5 例女性志愿者）。患者从出院到研究的平均时间为 169 天（范围，116-254 天）。患者与对照组志愿者 RBC/TP 比值存在差异（分别为 0.3±0.1 和 0.5±0.1； =.001；效应量，1.36）。志愿者与患者 RBC 和气相谱全宽半最大值之间存在显著差异（中位数±范围，567±1 与 507±81 [ =.002] 和 104±2 与 122±17 [ =.004]）。结果具有可重复性，患者和志愿者的组内相关系数分别为 0.82 和 0.88。参与者的 CT 扫描正常或几乎正常（平均，25 个中有 7 个；范围，25 个中有 0 个至 10 个）。结论 尽管 COVID-19 肺炎后 CT 检查结果正常或几乎正常，但超极化氙 129 MRI 结果显示所有 9 例患者的肺泡毛细血管扩散受限。
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