Morphological features of bronchiectasis in patients with non-tuberculous mycobacteriosis and interstitial pneumonia

Abstract

Objective: To compare the morphological features of bronchiectasis between patients with different underlying diseases, we performed quantitative analysis of high-resolution computed tomography (HRCT) images of 14 patients with non-tuberculous mycobacteriosis (NTM) and 13 with idiopathic pulmonary fibrosis (IPF). A 3D image of the bronchial structure was made from HRCT data. Bronchiectasis was defined as abnormal dilatation of the bronchi with the diameter greater than that of the accompanying pulmonary artery. We measured the inner and outer diameters, wall area as %total airway cross sectional area (WA%), and wall thickness to airway diameter ratio (T/D) of the 4-8th generations of bronchi.

Results: In patients with IPF, the inner and outer diameters linearly decreased toward the distal bronchi. In contrast, the inner and outer diameters of NTM fluctuated. The coefficient of variation of the outer diameters of the 6-7th generations of bronchi was larger in the NTM patients than in those with IPF, whereas no significant difference was observed in the coefficient of variation of the inner diameters between the groups. In IPF patients, WA% and T/D varied between the generation of bronchi, but the coefficient of variation of WA% and T/D was relatively small in those with NTM.

Keywords: 3D image; Bronchial structure; Bronchiectasis; Idiopathic pulmonary fibrosis; Non-tuberculous mycobacteriosis.

Fig. 1

Measurement procedure using a CT-3D imaging workstation. The bronchus to be measured was selected on the left CT image, and a bronchial pathway was created by automatic extraction (top). The bronchial cross section at the specified position is displayed and the inner and outer diameters are marked (bottom left). The inner and outer diameters, WA%, and T/D ratio were automatically calculated for the 4th-8th generations of bronchi (bottom right). L: lumen diameter, T: wall thickness, D: overall bronchial diameter. In the measurement screen, multiple measurements of T, D, and L are made, and their average are calculated

Fig. 2

Morphological parameters of bronchiectasis. A Outer diameter, B Inner diameter. In the patients with IPF, the outer and inner diameters decreased linearly toward the distal part of the bronchus. In contrast, some bronchi were larger at the distal part, and the outer and inner diameter measurements of a generation of the bronchi were largely different between the patients with NTM. C WA%, D T/D ratio. WA% and T/D ratio in most of the NTM patients increased linearly toward the distal part of the bronchus although the values were diverse between the subjects. In the patients with IPF, larger values of WA% and T/D ratio were observed at the distal part

Fig. 3

Schematic diagram of morphological features of bronchiectasis. Bronchiectasis in NTM patients has a larger lumen and thicker walls due to edematous changes of the bronchial wall, whereas IPF patients have a larger lumen and thinner airway wall due to traction along with the fibrosis of the surrounding alveoli