Imaging and lung disease: uses and interpretation

Diagnostic imaging has undergone a profound revolution since the first computed tomography (CT) unit was conceived in 1971; CT is now an integral part of daily practice in thoracic radiology, and has reached a relative technological maturity. Magnetic Resonance Imaging (MRI) has been introduced more recently. Technical difficulties still exist and are related to cardiac and respiratory motion. The storage-phosphor-based computed radiography system provides several advantages, including compensation for variations in exposure, but is still under evaluation especially in bedside radiography. Nevertheless careful plain film analysis still remains an important examination, and should be done before special procedures are taken to answer specific questions. Routine chest radiography is still the most frequent method of imaging employed today. Radiographic studies can suggest airway pathology such as atelectasis, endobronchial neoplasia or bronchiectasis, but CT provides a unique strategy for the localization and characterization of bronchial and pulmonary parenchymal disease. The most important role of CT is to determine, localize and characterize patterns within the pulmonary parenchyma, and correctly identify bronchiectasis even when bronchography is equivocal. In lung cancer, imaging has an important role in accurate staging with regard to the correct selection of patients and evaluation of prognosis. CT is one of the major tests used for staging. The staging system now adopted worldwide is based upon AJCC and ATS classification, and has two major components: anatomic extent of the disease (TNM) and cell types. The role of MRI with regard to lung cancer is not precisely determined. MRI can play a complementary role in the staging of lung cancer in cases of superior sulcus tumour; pericardial involvement, tumoral extension in subcarinal region and invasion of the superior vena cava. The radiologic detection of the solitary nodule is a difficult charge for the radiologist; CT provides the precise localization of the nodule and is reliable for analysing radiologic features such as calcification, cavitation, and spiculated borders. The problem remains of the discovery of an incidental benign pulmonary nodule in the patient with an extrathoracic malignancy, and often necessitates percutaneous biopsy under CT guidance. The evaluation of diffuse lung disease lies on pattern recognition. Chest radiography is the initial tool for diagnosis, high resolution CT (HRCT) can provide routine visualization of structures of less than 500 mu. HRCT can be useful in formulating a differential diagnosis with recognition of pattern and distribution of the disease.(ABSTRACT TRUNCATED AT 400 WORDS)