Differentiation of quantitative CT imaging phenotypes in asthma versus COPD

Area of Science:

• Pulmonary imaging and respiratory disease research.
• Quantitative CT (QCT) analysis of airway and parenchymal metrics.

Background:

• Asthma and Chronic Obstructive Pulmonary Disease (COPD) are distinct respiratory conditions.
• Quantitative CT (QCT) imaging offers objective metrics for disease characterization.
• Understanding similarities and differences in QCT metrics between asthma and COPD is crucial for diagnosis and management.

Purpose of the Study:

• To characterize similarities and disparities between asthma and COPD using QCT-derived airway and parenchymal metrics.
• To identify discriminant QCT variables between asthma and COPD patients.

Main Methods:

• Inspiratory and expiratory QCT scans were analyzed from 75 asthma, 215 COPD, and 94 healthy subjects (all with post-bronchodilator FEV1 <80%).
• Segmental airway variables (circularity, normalized wall thickness, normalized hydraulic diameter) and lobar parenchymal variables (emphysema, small-airway disease, tissue fraction, lung deformation) were computed.
• Image registration and density-based metrics were employed for detailed analysis.

Main Results:

• Both asthma and COPD subjects showed decreased airway circularity and normalized hydraulic diameter compared to healthy controls.
• COPD subjects exhibited more severe emphysema and small-airway disease, along with reduced tissue fraction and lung deformation, compared to asthma subjects.
• Differences in emphysema, small-airway disease, and tissue fraction between asthma and COPD were more pronounced in the upper and middle lobes.

Conclusions:

• Patients with asthma and COPD (FEV1 <80%) share similar airway geometric alterations but differ in parenchymal disease severity.
• Density-based QCT metrics from upper and middle lobes effectively discriminate between asthma and COPD.
• QCT provides valuable insights into the distinct pathological features of asthma and COPD.