Active Pulmonary Tuberculosis: Reliable Signs for Early Diagnosis by High Resolution CT (HRCT)
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Although standard chest radiographs usually provide adequate information for the diagnosis of active pulmonary tuberculosis, minimal lesions can be overlooked. The aim of the present study was to define the role of high resolution CT in the evaluation of active pulmonary tuberculosis including the sequential changes before and after therapy. This study included 40 patients with newly diagnosed pulmonary tuberculosis, studied prospectively. The diagnosis of active pulmonary tuberculosis was based on the detection of acid-fast bacilli in sputum or bronchial washing smears. HRCT scans and plain chest X-ray were obtained before the beginning of treatment, as well as 3 and 6 months during treatment. The lesions commonly identified on HRCT scanning included centrilobular nodules or linear lesions (100%), "tree in bud" appearance (90%), poorly defined nodules (75%) and cavitary lesions (60%). The follow up scans showed resolution of most of these lesions within 6 months after treatment except the centrilobular nodules. On the other hand, distortion of broncho-vascular structures, emphysema, fibrotic bands, bronchiectasis and loss of lung volume tended to increase or develop on follow up HRCT scans and chest radiographs as evidence of the healing process. We concluded that the centrilobular nodules and "tree in bud" appearance, are the most characteristic HRCT features of early active tuberculosis and are considered reliable criteria for monitoring the disease activity.