1 INTRODUCTION
Bronchiolitis obliterans (BO) is a chronic obstructive lung disease that leads to the irreversible obliteration of the small airways1,2. BO can occur with various etiologic factors, including infection, allogeneic hematopoietic stem cell transplantation (HSCT), and organ transplantation3. Bronchiolar epithelial cell and subepithelial structural damage and inflammation are the major pathogenesis of BO4.
Early diagnosis of BO in young children is particularly important, as it affects permanent lung function in the future. The diagnosis of BO is generally based on chest computed tomography (CT) images, along with a combination of PFTs or histologic findings. Common CT findings in patients with BO include bronchiectasis, bronchial wall thickening, and air trapping5. Conventionally, spirometry and chest CT findings have been suggested as the two most important standards for the diagnosis of BO. However, a clear diagnosis or assessment of the severity of early childhood BO can often be challenging, as the presence of lumen dilatation and bronchial wall thickening may be discrete or absent in the early stages, and poor coordination often makes PFTs difficult to complete. Hence, it is desirable to develop additional tools that can improve the diagnosis of BO among young children.
The purpose of this study was to evaluate the quantitative diagnostic performance of CT in pediatric BO patients by analyzing various lung density indices (LDIs) based on mean lung density (MLD) measured during inspiration and exhalation using the chest CT quantitative method.