Free-breathing Functional Pulmonary MRI: Response to Bronchodilator and Bronchoprovocation in Severe Asthma

Dante P I Capaldi; Khadija Sheikh; Rachel L Eddy; Fumin Guo; Sarah Svenningsen; Parameswaran Nair; David G McCormack; Grace Parraga; Canadian Respiratory Research Network

doi:10.1016/j.acra.2017.04.012

Free-breathing Functional Pulmonary MRI: Response to Bronchodilator and Bronchoprovocation in Severe Asthma

Acad Radiol. 2017 Oct;24(10):1268-1276. doi: 10.1016/j.acra.2017.04.012. Epub 2017 May 24.

Authors

Dante P I Capaldi¹, Khadija Sheikh¹, Rachel L Eddy¹, Fumin Guo², Sarah Svenningsen³, Parameswaran Nair⁴, David G McCormack⁵, Grace Parraga⁶; Canadian Respiratory Research Network

Affiliations

¹ Robarts Research Institute, The University of Western Ontario, London, Canada; Department of Medical Biophysics, The University of Western Ontario, London, Canada.
² Robarts Research Institute, The University of Western Ontario, London, Canada; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada.
³ Robarts Research Institute, The University of Western Ontario, London, Canada; Division of Respirology, Department of Medicine, McMaster University, Hamilton, Canada.
⁴ Division of Respirology, Department of Medicine, McMaster University, Hamilton, Canada.
⁵ Division of Respirology, Department of Medicine, The University of Western Ontario, London, Canada.
⁶ Robarts Research Institute, The University of Western Ontario, London, Canada; Department of Medical Biophysics, The University of Western Ontario, London, Canada; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada. Electronic address: gparraga@robarts.ca.

PMID: 28551402
DOI: 10.1016/j.acra.2017.04.012

Abstract

Rationale and objectives: 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 ¹H magnetic resonance imaging (FDMRI), and inhaled-gas MRI ventilation defect percent (VDP).

Materials and methods: 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 (FEV₁) >70%_predicted, MRI was also performed before and after MCh challenge. Wilcoxon signed-rank tests, Spearman correlations, and a repeated-measures analysis of variance were performed.

Results: Hyperpolarized ³He (P = .02) and FDMRI (P = .02) VDP significantly improved post-salbutamol and for four asthmatics who could perform MCh (n = 4). ³He and FDMRI VDP significantly increased at the provocative concentration of MCh, resulting in a 20% decrease in FEV₁ (PC₂₀) and decreased post-bronchodilator (P = .02), with a significant difference between methods (P = .01). FDMRI VDP was moderately correlated with ³He VDP (ρ = .61, P = .01), but underestimated VDP relative to ³He VDP (-6 ± 9%). Whereas ³He MRI VDP was significantly correlated with the lung clearance index, FDMRI was not (ρ = .49, P = .06).

Conclusions: FDMRI VDP generated in free-breathing asthmatic patients was correlated with static inspiratory breath-hold ³He MRI VDP but underestimated VDP relative to ³He MRI VDP. Although less sensitive to salbutamol and MCh, FDMRI VDP may be considered for asthma patient evaluations at centers without inhaled-gas MRI.

Keywords: Fourier decomposition; asthma; hyperpolarized noble gas; magnetic resonance imaging; treatment response.

MeSH terms

Adult
Albuterol / therapeutic use
Asthma / diagnostic imaging*
Asthma / drug therapy
Asthma / physiopathology*
Bronchoconstrictor Agents
Bronchodilator Agents / therapeutic use
Female
Humans
Image Processing, Computer-Assisted
Lung / diagnostic imaging*
Lung / physiopathology*
Magnetic Resonance Imaging / methods*
Male
Methacholine Chloride
Middle Aged
Plethysmography / methods
Respiration
Respiratory Function Tests
Spirometry / methods

Substances

Bronchoconstrictor Agents
Bronchodilator Agents
Methacholine Chloride
Albuterol

Grants and funding

MOP 201309/CIHR/Canada