Automated Volumetric Quantification of Emphysema Severity by Using Ultrashort Echo Time MRI: Validation in Participants with Chronic Obstructive Pulmonary Disease

Abstract

hronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation (1) and is the third leading cause of mortality worldwide (2). In the past decades, chest CT has helped to provide valuable insights into COPD. Indeed, CT enables noninvasive, in vivo, and three-dimensional (3D) quantification of the key components of the disease, such as bronchial remodeling (3) and emphysema (4). Evidence of COPD subtypes (1), relationship with genetic variants (5), longitudinal follow-up (6), and mortality (7) have been investigated at CT. More recently, in an era where the advent of artificial intelligence may allow intricate combinations of both morphologic and functional information, lung MRI has emerged as a radiation-free modality for the longitudinal follow-up of lung diseases and (8) to help better identify participant phenotype or predict disease outcomes (9). Studies related to ventilation (10), perfusion (11), dynamic biomarkers (12), and coupling between the cardiovascular and pulmonary systems (13,14) at MRI have been performed. However, there are few studies that evaluated the regional extent of emphysema by using MRI (15-18). Recent advances with ultrashort echo times (UTEs) have been shown to enable submillimeter resolution with good contrast in three dimensions (19,20).

The Clinical Use of Lung MRI in Cystic Fibrosis

“…32 Therefore, complementary softwarebased quantitative tools have been emphasized to enable objective and reproducible assessment for more standardized evaluation. Three-dimensional measurement of the central bronchial tree, at functional residual capacity, 33 or the amount of emphysema 34 (Fig 2 ) has been proven using 3D-UTE. A quantitative volumetric measurement of structural abnormalities by UTE also demonstrated clinical relevance to discriminate CF with exacerbation and to detect their longitudinal improvement after a 1-year follow-up, although PFT results were found to be stable.…”

Structural and functional changes in COPD: What we have learned from imaging

“…Using this novel MR modality, detection and visual description of emphysema can be accurately performed. 71,72 Another difficulty using MRI is quantitative measurement of disease severity, because in comparison to CT, the MR signal is not calibrated. Thus, any quantitative index cannot rely on absolute measurement values.…”

“…The acquisition is made in free‐breathing mode, and there is no need for a contrast product injection. Using this novel MR modality, detection and visual description of emphysema can be accurately performed 71,72 …”

“…Thus, any quantitative index cannot rely on absolute measurement values. Adaptative solutions have been developed and validated to demonstrate that quantifying the volume of emphysema is feasible using UTE MRI 68,71,72 (Figure 4). Also, correlations of lung signal‐intensity with pulmonary function and CT measurements of emphysema were reported in COPD patients exhibiting variable degrees of emphysema severity 68,72 .…”

<p>Assessing pulmonary hypertension in COPD. Is there a role for computed tomography?</p>

“…Other interesting technics could be used to study PH, such as Dual energy CT,29 or magnetic resonance imaging (MRI). MRI is much less employed in lung diseases due to the low signal intensity of the lung but recent improvements have been published30–34 and MRI is currently the best tool for evaluating heart morphology and function,35 or estimating pulmonary arterial pressure using phase contrast MRI 36…”