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To evaluate findings of active pulmonary tuberculosis on computed tomographic (CT) scans and their sequential changes before and after antituberculous chemotherapy, 29 patients with newly diagnosed pulmonary tuberculosis and 12 patients with recent reactivation were studied prospectively. The diagnosis of active pulmonary tuberculosis was based on positive acid-fast bacilli in sputum (n = 29) and changes on serial radiographs obtained during treatment (n = 12). Twenty-six patients were followed up with CT during treatment for 1-20 months. Lungs from the cadavers of nine other patients, who died of pulmonary tuberculosis, were studied to provide a pathologic basis for diagnosis. At examination with CT, centrilobular lesions (nodules or branching linear structures 2-4 mm in diameter) were most commonly seen (n = 39 [95%]); in the 26 patients with follow-up, most of these lesions disappeared within 5 months after the start of treatment. In 11 of 12 patients with recent reactivation, CT clearly differentiated old fibrotic lesions from new active lesions. Lesions in and around the small airways appear to be the most characteristic CT feature of early active tuberculosis and may be a reliable criterion for disease activity.

Pulmonary tuberculosis (TB) is a common worldwide infection and a medical and social problem causing high mortality and morbidity, especially in developing countries. The traditional imaging concept of primary and reactivation TB has been recently challenged, and radiologic features depend on the level of host immunity rather than the elapsed time after the infection. We aimed to elaborate the new concept of the diagnosis and treatment of pulmonary TB, to review the characteristic imaging findings of various forms of pulmonary TB, and to assess the role of CT in the diagnosis and management of pulmonary TB. Fast and more accurate TB testing such as bacterial DNA fingerprinting and whole-blood interferon-gamma assay has been developed. Miliary or disseminated primary pattern or atypical manifestations of pulmonary TB are common in patients with impaired immunity. CT plays an important role in the detection of TB in patients in whom the chest radiograph is normal or inconclusive, in the determination of disease activity, in the detection of complication, and in the management of TB by providing a roadmap for surgical treatment planning. PET scans using 18F-FDG or 11C-choline can sometimes help differentiate tuberculous granuloma from lung malignancy.

Although chest radiographs usually provide adequate information for the diagnosis of active pulmonary tuberculosis, minimal exudative tuberculosis can be overlooked on standard chest radiographs. The aim of the present study was to assess the findings of active pulmonary tuberculosis on high resolution computed tomographic (HRCT) scans, and to evaluate their possible use in determining disease activity. Thirty two patients with newly diagnosed active pulmonary tuberculosis and 34 patients with inactive pulmonary tuberculosis were examined. The diagnosis of active pulmonary tuberculosis was based on positive acid fast bacilli in sputum and bronchial washing smears or cultures and/or changes on serial radiographs obtained during treatment. With HRCT scanning centrilobular lesions (n = 29), "tree-in-bud" appearance (n = 23), and macronodules 5-8 mm in diameter (n = 22) were most commonly seen in cases of active pulmonary tuberculosis. HRCT scans showed fibrotic lesions (n = 34), distortion of bronchovascular structures (n = 32), emphysema (n = 28), and bronchiectasis (n = 24) in patients with inactive tuberculosis. Centrilobular densities in and around the small airways and "tree-in-bud" appearances were the most characteristic CT features of disease activity. HRCT scanning clearly differentiated old fibrotic lesions from new active lesions and demonstrated early bronchogenic spread. These findings may be of value in decisions on treatment.