Chest radiographic evaluation of diffuse infiltrative lung disease: review of a dying art.
- Wallace T Miller
- European journal of radiology
Plain chest radiography remains the first diagnostic approach to diffuse infiltrative lung disease but has limited diagnostic sensitivity and specificity. Many diseases remain occult or are not correctly assessed using chest Xray, appearing as a nonspecific ‘reticulonodular pattern’. High-resolution CT (HRCT) is actually the recommended imaging technique in the diagnosis, assessment, and follow-up of these diseases, allowing also the evaluation of the effectiveness of the medical therapy and the selection of the type and the location of the biopsy when required. Appropriate techniques must be used to acquire highquality HRCT scans, with the thin collimation and high spatial reconstruction algorithm being the most important factors. A nodular pattern, linear and reticular opacities, cystic lesions, ground-glass opacities and consolidations are the most common HRCT patterns of diffuse infiltrative lung disease. This article reviews the role of chest radiography and HRCT in the diagnosis and assessment of these diseases, the technical aspects of HRCT, its clinical indications and the radiological pattern of the most common types of chronic diffuse infiltrative lung disease. Copyright © 2004 S. Karger AG, Basel Introduction The radiological diagnostic approach to diffuse infiltrative lung disease is classically based on chest X-ray evaluation. Among the most difficult tasks in radiology, chest X-rays remain unsurpassed in relation to its costs, radiation dose, availability, and ease of performance. However, chest radiography has substantial limitations: it is normal in 10–15 percent of symptomatic patients with proven infiltrative lung disease [1, 2]; it can mimic interstitial disease in patients with different lung lesions (e.g. paraseptal emphysema and small-airway disease), and it is often quite nonspecific although abnormal. Peripheral reticular, cystic, linear, nodular lesions and ground-glass density are the main radiological patterns used in the plain film interpretation of diffuse lung disease.Unfortunately, interstitial lung disease often appears in a non-specific ‘reticulonodular’ pattern . The distribution of the opacities and the clinical history play a fundamental role in the assessment of nonspecific patterns. In several studies, overall sensitivity and specificity of chest X-rays were 80 and 82%, respectively, for the detection of diffuse lung disease; a confident diagnosis was possible in only 23% of cases, which proved to be correct in 77% . Since 1982, when Todo et al.  first described the HRCT technique, the high correlation between HRCT D ow nl oa de d by : 54 .1 91 .4 0. 80 9 /1 7/ 20 17 2 :2 4: 14 P M Diffuse Infiltrative Disease Respiration 2004;71:4–19 5 findings and abnormalities seen on corresponding inflation-fixed lung specimens aroused great interest [5, 6]. For the first time, the secondary pulmonary lobule and anatomic details as interlobar fissures, interlobular septa, centrilobular arterial branches and, in some cases, the thin intralobular septa could be correctly identified with a radiological method. Presently, more than 20 years after its introduction, HRCT is considered the best imaging tool in this field of application for the evaluation of the pulmonary interstitium and secondary pulmonary lobule to diagnose and assess diffuse lung disease. Several authors have reported a sensitivity of 95% and a specificity approaching 100% for HRCT in disease detection [4, 7]. A confident specific diagnosis has been possible in about one half of the cases, and these diagnoses proved correct in 93% compared to 77% with chest Xrays. Grenier et al.  assessed, using Bayesian analysis, the sequential value of clinical chest-radiographic and CT findings in classifying chronic diffuse infiltrative lung disease. The authors showed an incremental diagnostic benefit for HRCT: in a series of 100 patients with diffuse lung disease, an accurate diagnosis was made on the basis of clinical data in only 27% of the cases, increasing to 53% combined with radiographic findings and to 61% with CT data. This article reviews the role of chest radiography and HRCT in the diagnosis and management of diffuse infiltrative lung diseases, the technical aspects of HRCT, its clinical indications and the radiological patterns of the most common diseases. Anatomic Considerations and Technical