CT QUANTIFICATION OF INTERSTITIAL FIBROSIS IN PATIENTS WITH ASBESTOSIS - A COMPARISON OF 2 METHODS

OBJECTIVE. The likelihood of interstitial lung disease being detected on high-resolution CT scans and having functional significance is ofte n related to the severity of the disease. The extent and severity of t he abnormalities seen on high-resolution CT are usually assessed subje ctively. This study was undertaken to investigate whether a subjective semiquantitative scoring method or a method using a cumulation of the different high-resolution CT features of asbestosis were comparable i n suggesting asbestosis in a group of patients with histopathologic co nfirmation of disease. A secondary objective was to compare the result s of these two high-resolution CT methods with chest radiographs in th e same population. MATERIALS AND METHODS. This study group consisted o f 24 patients and six lungs obtained at autopsy. Histopathologic asbes tosis was present in 25 of the 30 patients or lungs. The patients or l ungs were imaged using selected high-resolution CT scans. The high-res olution CT scans were assessed in two ways. One used a subjective semi quantitative extent and severity score consisting of four levels of se verity, while the other was a cumulative score adding the different ty pes of high-resolution abnormalities in asbestosis. The commonest high -resolution CT abnormalities in the cases with confirmed asbestosis we re interstitial lines (84%), parenchymal bands (76%), and architectura l distortion of secondary pulmonary lobules (56%). Subpleural lines an d honeycombing were less frequent. The histopathologic severity of asb estosis was independently graded on a four-point scale. Chest radiogra phs, when available, were classified according to the International La bor Organization (ILO) classification of pneumoconioses. RESULTS. With the subjective semiquantitative high-resolution CT severity score, as bestosis was suggested in 16 (64%) instances, all with disease. With t he cumulative method, any one type of abnormality was present in 88% o f cases with asbestosis, two types in 78%, and three in 56%. However, to include only cases with asbestosis, three different abnormalities h ad to be present. The high-resolution CT scans were normal or near nor mal in five instances of asbestosis. Chest radiographs using the ILO c lassification predicted asbestosis with a lesser frequency than high-r esolution CT in this selected population. CONCLUSION. We conclude that a subjective semiquantitative grading system of the extent and severi ty of asbestosis and a method using a cumulative addition of the diffe rent findings in asbestosis give similar results in suggesting the pre sence of disease. Thus, for the high-resolution CT detection of asbest osis, a combination of the cumulative number of different findings and an assessment of the extent and severity of the abnormalities could b e complimentary. We also conclude that asbestosis can be present histo pathologically with a normal or near normal high-resolution CT scan.