Quantitative analysis of lung function and airway remodeling using ventilation/perfusion single photon emission tomography/computed tomography in patients with chronic obstructive pulmonary disease and asthma

Introduction: Chronic obstructive pulmonary disease (COPD) and asthma are heterogeneous diseases, which means that accurate and detailed information about local structural and functional abnormalities is needed to better characterize the severity of the disease and to improve the choice of potential treatments. It is generally accepted that FEV1 cannot describe the complexity of chronic airway disease or the underlying pathophysiology and cannot be used alone for optimal assessment and management of the disease. Our purpose is to investigate the role of ventilation/perfusion single photon emission tomography/computed tomography (V/P SPECT/CT) quantitative parameters in evaluating COPD and asthma disease severity, airway obstruction degree, ventilation and perfusion distribution patterns, airway remodeling, and lung parenchymal changes.

Methods: Fifty-three subjects, including patients with COPD or asthma, and healthy controls, who underwent V/P SPECT/CT, high-resolution computed tomography (HRCT), and pulmonary function tests (PFTs) were included. Preserved lung ventilation (PLVF), perfusion function (PLPF), degree of airway obstruction (OG), proportion of anatomical volume, ventilation and perfusion contribution of each lobe, volume perfusion ratio, and V/P distribution patterns were evaluated using V/P SPECT/CT. The quantitative parameters of HRCT included CT bronchial and CT pulmonary function parameters. In addition, V/P SPECT/CT-, HRCT-, and PFT-related parameters were compared.

Results: The OG and PLVF, PLPF, and PFT parameters were significantly correlated, with FEV1 correlation being the most significant (r=-0.901, r=0.915, and r=0.836, respectively). There was a strong negative correlation between OG and PLVF (r=-0.945) and OG and PLPF (r=-0.853), and a strong positive correlation between PLPF and PLVF (r=0.872). In addition, OG, PLVF, and PLPF were moderate to strongly correlated with CT lung function parameters; the correlation with both lung EIs was the strongest (r=0.81, r=-0.839, and r=-0.754, respectively; P<0.01). In addition, OG, PLVF, and PLPF showed low to moderate correlations with most CT bronchial parameters (r=-0.366 ~ -0.663, P<0.01). The CT lung function parameters were all moderately to strongly correlated with PFT (r=-0.611 ~ -0.860, P<0.01), unlike the SPECT parameters. There were three different V/P distribution patterns, including matched, mismatched, and reverse mismatched patterns. Lastly, the CT volume overestimated the contribution in the upper lobes and underestimated the lower lobes’ contribution to overall function.

Conclusions: V/P SPECT/CT can provide information on airway remodeling and pulmonary function changes in COPD and asthma, assessing the impairment of regional pulmonary function and grading the degree of airway obstruction. In addition, V/P SPECT/CT was superior to HRCT in evaluating lung function, and this study revealed the differences between the CT anatomical volumes and ventilation and perfusion contributions. SPECT imaging complements global respiratory function measurements by adding regional functional and morphologic information for ventilation and perfusion.

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