Inhomogeneous lung densities in high resolution computed tomography

High resolution computed tomography (HRCT) is an imaging modality,which achieves high quality images of lung anatomy. HRCT is imaging modality of choice in evaluating of lung parenchyma. In HRCT imaging of small differences in lung density is possible, which are invisible in plane radiograms and standard CT. The aim of the study is analyzing of HRCT diagnostic possibilities in revealing and differentiating of causes of inhomogeneous lung density. Material comprises of a group of 118 patients, in which HRCT examination was performed due to interstitial lung diseases. Examinations were performed with SOMATOM ART scanner by Siemens, equipped with matrix sized 512x512 pixels and software enabling examination in high resolution protocol. Examination was performed at full inspiration in supine patients positions. Additional expiratory sections were also obtained. In which patients the frequency and statistical significance of ground glass opacities,mosaic perfusion and air-trapping were evaluated. The presence of ground glass opacities correlated significantly with sarcoidosis,pneumoconiosis and interstitial pneumonia,in which they were present in 76%, 79% and 95%, respectively. The mosaic perfusion was seen in HRCT predominantly in patients with bronchiolitis (in 79%), and was statistically significant finding for bronchiolitis. The air-trapping was statistically significant only for bronchiolitis, in which it was seen in 95% patients. Inhomogeneous lung density in HRCT examination may be caused by ground glass opacity, air-trapping, mosaic perfusion and emphysema. The expiratory HRCT is important in differentiating those reasons of inhomogeneous lung density. The mosaic perfusion and air-trapping are typical findings in bronchiolitis, although may be found in different diseases. Ground glass opacity is typical for inflammatory lung diseases. (author)