Firestone Institute for Respiratory Health, St. Joseph's Healthcare Hamilton, Hamilton, Canada; Department of Medicine, McMaster University, 50 Charlton Avenue East, Hamilton, Ontario, Canada L8N 4A6.
Robarts Research Institute, Western University, London, Canada; Department of Medical Biophysics, Western University, London, Canada.
Acad Radiol. 2021 Jun;28(6):817-826. doi: 10.1016/j.acra.2020.04.025. Epub 2020 May 14.
Xe 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 Xe ventilation MRI measurements in severe asthmatics at two sites.
In seven adults with severe asthma, Xe ventilation MRI was acquired pre- and post-bronchodilator at two geographic sites within 24-hours. Xe 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 Xe VDP reproducibility and agreement.
Whole-lung and slice-by-slice Xe 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 Xe-dose-equivalent-volume (101 ± 15 mL site 1, 49 ± 6 mL site 2, p < 0.0001), gas-mixture (Xe/He site 1; Xe/N site 2) and SNR (40 ± 19 site 1, 23 ± 5 site 2, p = 0.02). Qualitative Xe gas distribution differences were observed between sites and slice-by-slice Xe VDP, but not whole-lung Xe 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).
Xe MRI VDP at two different sites measured within 24-hours in the same severe asthmatics were correlated. Qualitative and quantitative intersite differences in Xe regional gas distribution and VDP point to site-specific variability that may be due to differences in gas-mixture composition or SNR.
Xe MRI 已被开发用于无创可视化和定量评估哮喘患者气道阻塞的功能后果。为了广泛应用 Xe MRI，需要提供其在不同地点的可重复性和一致性的证据。我们的目标是评估两名受试者在两个不同地点的重度哮喘患者的 Xe 通气 MRI 测量的可重复性和一致性。
七名重度哮喘患者在 24 小时内先后在两个不同地点进行了支气管扩张剂前后的 Xe 通气 MRI 检查。计算 Xe MRI 信号与噪声比（SNR），并将通气异常量化为全肺和逐层的通气缺损百分比（VDP）。采用组内相关系数（ICC）和 Bland-Altman 分析来确定不同地点 Xe VDP 的可重复性和一致性。
两个部位的全肺和逐层 Xe VDP 均具有相关性和可重复性（支气管扩张剂前：全肺 ICC=0.90，p=0.005，逐层 ICC=0.78，p<0.0001；支气管扩张剂后：全肺 ICC=0.94，p<0.0001，逐层 ICC=0.83，p<0.0001），尽管 Xe 剂量等效体积（101±15ml 部位 1，49±6ml 部位 2，p<0.0001）、气体混合物（部位 1 Xe/He；部位 2 Xe/N）和 SNR（40±19 部位 1，23±5 部位 2，p=0.02）存在差异。尽管如此，仍观察到两个部位的 Xe 气体分布存在定性差异，且逐层 Xe VDP 低于全肺 Xe VDP，但仅在部位 1 存在显著差异（支气管扩张剂前 VDP：全肺偏差=–3%，p>0.99，逐层偏差=–3%，p=0.0001；支气管扩张剂后 VDP：全肺偏差=–2%，p=0.59，逐层偏差=–2%，p=0.0003）。
同一重度哮喘患者在 24 小时内于两个不同地点进行的 Xe MRI VDP 具有相关性。Xe 区域性气体分布和 VDP 的定性和定量的不同提示存在与部位相关的可变性，这可能是由于气体混合物组成或 SNR 的差异所致。
