[Analysis of pyrophillitosis by high-resolution computed tomography].

High-resolution computed tomography (HR-CT) was performed on 20 patients with pyrophilitosis. Small nodular opacities in these patients could be divided by HR-CT into two types, namely, tiny irregular branching structures (TIB) and small round opacities (SRO). TIB had a centrilobular distribution and were characteristic of pyrophillitosis. SRO had both centrilobular and perilobular distributions and were considered to be changes modified by the aspiration of silica. Large opacities (LO) of pyrophillitosis were classified into three types, that is, spherical type, flat type parallel to the bronchus and flat type parallel to the thoracic wall. The spherical type was seen in patients exposed to both pyrophillite and silica, while the flat types were seen in patients exposed to only pyrophillite and were characteristic opacities of pyrophillitosis. Pulmonary emphysema was found in only one patient with pyrophillitosis, whereas mediastinal lymph node swelling and calcification were seen in most patients with pyrophillitosis. HR-CT is useful in making a more accurate evaluation of these lesions.