Ventilation heterogeneity in ex-smokers without airflow limitation

Damien Pike; Miranda Kirby; Fumin Guo; David G McCormack; Grace Parraga

doi:10.1016/j.acra.2015.04.006

Ventilation heterogeneity in ex-smokers without airflow limitation

Acad Radiol. 2015 Aug;22(8):1068-78. doi: 10.1016/j.acra.2015.04.006. Epub 2015 May 23.

Authors

Damien Pike¹, Miranda Kirby², Fumin Guo³, David G McCormack⁴, Grace Parraga⁵

Affiliations

¹ Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; Department of Medical Biophysics, The University of Western Ontario, London, Canada.
² James Hogg Research Centre, St. Paul's Hospital, University of British Columbia, Vancouver, Canada.
³ Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada.
⁴ Division of Respirology, Department of Medicine, The University of Western Ontario, London, Canada.
⁵ Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; 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: 26008133
DOI: 10.1016/j.acra.2015.04.006

Abstract

Rationale and objectives: Hyperpolarized (3)He magnetic resonance imaging (MRI) ventilation abnormalities are visible in ex-smokers without airflow limitation, but the clinical relevance of this is not well-understood. Our objective was to phenotype healthy ex-smokers with normal and abnormally elevated ventilation defect percent (VDP).

Materials and methods: Sixty ex-smokers without airflow limitation provided written informed consent to (3)He MRI, computed tomography (CT), and pulmonary function tests in a single visit. (3)He MRI VDP and apparent diffusion coefficients (ADCs) were measured for whole-lung and each lung lobe as were CT measurements of emphysema (relative area [RA] with attenuation ≤-950 HU, RA950) and airway morphology (wall area percent [WA%], lumen area [LA] and LA normalized to body surface area [LA/BSA]).

Results: In 42 ex-smokers, there was abnormally elevated VDP and no significant differences for pulmonary function, RA950, or airway measurements compared to 18 ex-smokers with normal VDP. Ex-smokers with abnormally elevated VDP reported significantly greater (3)He ADC in the apical lung (right upper lobe [RUL], P = .02; right middle lobe [RML], P = .04; and left upper lobe [LUL], P = .009). Whole lung (r = 0.40, P = .001) and lobar VDP (RUL, r = 0.32, P = .01; RML, r = 0.46, P = .002; right lower lobe [RLL], r = 0.38, P = .003; LUL, r = 0.35, P = .006; and left lower lobe, r = 0.37, P = .004) correlated with regional (3)He ADC. Although whole-lung VDP and CT airway morphology measurements were not correlated, regional VDP was correlated with RUL LA (r = -0.37, P = .004), LA/BSA (r = -0.42, P = .0008), RLL WA% (r = 0.28, P = .03), LA (r = -0.28, P = .03), and LA/BSA (r = -0.37, P = .004).

Conclusions: Abnormally elevated VDP in ex-smokers without airflow limitation was coincident with very mild emphysema detected using MRI and regional airway remodeling detected using CT representing a subclinical obstructive lung disease phenotype.

Keywords: Hyperpolarized (3)He magnetic resonance imaging; airways disease; computed tomography; emphysema.

Publication types

Comparative Study
Controlled Clinical Trial
Research Support, Non-U.S. Gov't

MeSH terms

Aged
Emphysema / physiopathology*
Female
Helium*
Humans
Image Interpretation, Computer-Assisted / methods
Isotopes
Magnetic Resonance Imaging / methods*
Male
Pulmonary Disease, Chronic Obstructive / physiopathology
Pulmonary Ventilation*
Radiopharmaceuticals
Reference Values
Reproducibility of Results
Sensitivity and Specificity
Smoking / physiopathology*
Smoking Cessation*

Substances

Isotopes
Radiopharmaceuticals
Helium

Grants and funding

MOP 106437/Canadian Institutes of Health Research/Canada