Capaldi Dante P I, Sheikh Khadija, Eddy Rachel L, Guo Fumin, Svenningsen Sarah, Nair Parameswaran, McCormack David G, Parraga Grace
Robarts Research Institute, The University of Western Ontario, London, Canada; Department of Medical Biophysics, The University of Western Ontario, London, Canada.
Robarts Research Institute, The University of Western Ontario, London, Canada; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada.
Acad Radiol. 2017 Oct;24(10):1268-1276. doi: 10.1016/j.acra.2017.04.012. Epub 2017 May 24.
Ventilation heterogeneity is a hallmark feature of asthma. Our objective was to evaluate ventilation heterogeneity in patients with severe asthma, both pre- and post-salbutamol, as well as post-methacholine (MCh) challenge using the lung clearance index, free-breathing pulmonary H magnetic resonance imaging (FDMRI), and inhaled-gas MRI ventilation defect percent (VDP).
Sixteen severe asthmatics (49 ± 10 years) provided written informed consent to an ethics board-approved protocol. Spirometry, plethysmography, and multiple breath nitrogen washout to measure the lung clearance index were performed during a single visit within 15 minutes of MRI. Inhaled-gas MRI and FDMRI were performed pre- and post-bronchodilator to generate VDP. For asthmatics with forced expiratory volume in 1 second (FEV) >70%, MRI was also performed before and after MCh challenge. Wilcoxon signed-rank tests, Spearman correlations, and a repeated-measures analysis of variance were performed.
Hyperpolarized He (P = .02) and FDMRI (P = .02) VDP significantly improved post-salbutamol and for four asthmatics who could perform MCh (n = 4). He and FDMRI VDP significantly increased at the provocative concentration of MCh, resulting in a 20% decrease in FEV (PC) and decreased post-bronchodilator (P = .02), with a significant difference between methods (P = .01). FDMRI VDP was moderately correlated with He VDP (ρ = .61, P = .01), but underestimated VDP relative to He VDP (-6 ± 9%). Whereas He MRI VDP was significantly correlated with the lung clearance index, FDMRI was not (ρ = .49, P = .06).
FDMRI VDP generated in free-breathing asthmatic patients was correlated with static inspiratory breath-hold He MRI VDP but underestimated VDP relative to He MRI VDP. Although less sensitive to salbutamol and MCh, FDMRI VDP may be considered for asthma patient evaluations at centers without inhaled-gas MRI.
通气异质性是哮喘的一个标志性特征。我们的目的是使用肺清除指数、自由呼吸肺部氢磁共振成像（FDMRI）和吸入气体MRI通气缺陷百分比（VDP），评估重度哮喘患者在使用沙丁胺醇前后以及乙酰甲胆碱（MCh）激发试验后的通气异质性。
16名重度哮喘患者（49±10岁）书面知情同意一项经伦理委员会批准的方案。在MRI检查的15分钟内的单次就诊期间，进行肺活量测定、体积描记法和多次呼吸氮洗脱以测量肺清除指数。在支气管扩张剂使用前后进行吸入气体MRI和FDMRI检查以生成VDP。对于一秒用力呼气容积（FEV）>70%的哮喘患者，在MCh激发试验前后也进行MRI检查。进行了Wilcoxon符号秩检验、Spearman相关性分析和重复测量方差分析。
超极化氦气（P = 0.02）和FDMRI（P = 0.02）的VDP在使用沙丁胺醇后以及对于4名能够进行MCh激发试验的哮喘患者（n = 4）有显著改善。在MCh激发浓度下，氦气和FDMRI的VDP显著增加，导致FEV（PC）下降20%，支气管扩张剂使用后下降（P = 0.02），不同方法之间有显著差异（P = 0.01）。FDMRI的VDP与氦气VDP中度相关（ρ = 0.61，P = 0.01），但相对于氦气VDP低估了VDP（-6±9%）。虽然氦气MRI的VDP与肺清除指数显著相关，但FDMRI与肺清除指数无相关性（ρ = 0.49，P = 0.06）。
自由呼吸哮喘患者中生成的FDMRI的VDP与静态吸气屏气氦气MRI的VDP相关，但相对于氦气MRI的VDP低估了VDP。尽管对沙丁胺醇和MCh的敏感性较低，但对于没有吸入气体MRI设备的中心，在评估哮喘患者时可考虑使用FDMRI的VDP。
