Small hyperdense nodules are nodular opacities measuring less than 10 mm in diameter, showing focal or diffuse distribution in the lung parenchyma. Small hyperdense nodules can be secondary to dystrophic calcification in previously damaged lung parenchyma. Small calcified parenchymal nodules most commonly are a result of infectious diseases. Other causes of small hyperdense nodules are pulmonary metastases, chronic haemorrhagic conditions, occupational diseases, deposition diseases, talcosis and idiopathic disorders such as pulmonary alveolar microlithiasis [1-3].
Calcified parenchymal nodules are frequently seen in tuberculosis. The sequela dystrophic calcification follows caseation, necrosis or fibrosis. These nodules are seen as well circumscribed parenchymal calcifications with fibrosis on CT (Fig. 1). Most patients with pulmonary nodular calcifications secondary to tuberculosis have calcified hilar or mediastinal lymph nodes, known together as the Ranke complex. Histoplasmosis and varicella infections may less commonly lead to parenchymal calcified nodules [1]. Widespread micronodular calcification can be seen in the late period of varicella infection.
Bạn đang xem: CT findings of high-attenuation pulmonary abnormalities
Metastatic pulmonary calcification is a consequence of calcium deposition in normal pulmonary parenchyma. This condition can occur in a variety of benign and malignant disorders such as primary and secondary hyperparathyroidism, chronic renal failure, sarcoidosis, vitamin D intoxication, IV calcium therapy, multiple myeloma and massive osteolysis caused by metastases [4]. High-resolution CT (HRCT) findings are characterised by centrilobular fluffy ground-glass nodular opacities that contain foci of calcification (Fig. 2). Metastatic pulmonary calcification is typically most marked in the upper lobes.
Xem thêm : Biotin
Idiopathic pulmonary haemosiderosis is an uncommon cause of alveolar haemorrhage that occurs predominantly in infants and young adults. This disorder is characterised by recurrent episodes of alveolar haemorrhage. HRCT shows dense centrilobular nodular opacities due to recurrent haemorrhage. Secondary haemosiderosis due to mitral stenosis may present with small calcified nodules.
Diffuse small calcified nodules, often associated with egg-shell calcification of hilar or mediastinal lymph nodes, can occur in silicosis and coal workers’ pneumoconiosis. Silicosis is caused by inhalation of free silica particles, usually during occupational exposure such as mining, sandblasting and masonry. Radiographic evidence of silicosis typically develops after 10-20 years of exposure to low concentrations of silica dust [5]. HRCT findings of silicosis include diffuse and randomly distributed small well-defined nodules that are most prominent in the upper lobes [6]. These calcified nodules are commonly seen with massive fibrosis (Fig. 3).
Multiple dense nodular opacities are rarely seen in siderosis, stannosis and baritosis, in which iron, tin and barium respectively are deposited in the lungs. In siderosis, nodular opacities are less dense and less profuse than those in silicosis. HRCT shows extremely dense opacities due to barium aspiration in baritosis, usually locating in the basal segments of the lower lobes (Fig. 4).
Xem thêm : Bookshelf
Alveolar microlithiasis, a rare disease of unknown origin, is characterized by diffuse sand-like calcifications within the alveoli. This disorder may be detected incidentally on chest radiographs obtained for other reasons. Characteristic HRCT findings consist of multiple innumerable tiny sand-like calcified micronodules that tendency toward confluence throughout both lungs. Other findings include calcified interlobular septa and small subpleural cysts. Another feature seen on HRCT includes a very low attenuation line alongside the pleura, called the “black pleural line” (Fig. 5).
Talcosis is seen in workers exposed to talc during extraction of magnesium silicate from mines and grinding. Another form of talcosis can be seen in drug users who inject talc. When dissolved and injected intravenously, talc particles become deposited within pulmonary arterioles, capillaries and interstitium.
HRCT findings consist of numerous high-attenuation well-defined micronodules or diffuse ground-glass opacities. Over time the nodules tend to confluence, resulting in high-attenuation confluent masses.
Nguồn: https://blogtinhoc.edu.vn
Danh mục: Info