Mean bronchial wall attenuation value in chronic obstructive pulmonary disease: comparison with standard bronchial parameters and correlation with function.

OBJECTIVE: The objective of our study was to evaluate bronchial wall attenuation values quantified using CT in patients with chronic obstructive pulmonary disease (COPD). SUBJECTS AND METHODS: Ninety patients (81 men, nine women; age range, 21-80 years; mean age, 56 years) underwent CT and pulmonary function tests (PFTs). Bronchial wall attenuation value, wall area, and lumen area were averaged over four segmental bronchi in control subjects (n = 30), smokers with COPD (n = 30), and smokers without COPD (n = 30). The bronchial wall thickness, wall area-to-lumen area ratio, and wall area-to-total area ratio were computed. The extent of emphysema was measured as the percentage of area with an attenuation of less than -950 HU. Parameters were compared among groups and were correlated with PFT results. Receiver operating characteristic curves were obtained for each parameter and areas under the curve were compared. Variables responsible for changes in wall attenuation values and those accounting for obstructive indexes were assessed using multiple regressions.
RESULTS: The wall attenuation value was the only parameter discriminating between each pair of groups (mean ± SD, -293 ± 71 HU in COPD patients, -387 ± 70 HU in smokers, and -457 ± 69 HU in control subjects). The area under the curve of the wall attenuation value was greater than that of any other CT bronchial parameter to separate smokers from COPD patients. Wall attenuation value correlated with PFT results and was influenced by the wall area-to-lumen area ratio. The wall attenuation value, extent of emphysema, and standard bronchial parameters independently influenced obstructive indexes.
CONCLUSION: The bronchial wall attenuation value is a powerful index for assessing tobacco-related bronchial wall changes in patients with COPD.