Computed Tomography of the Pulmonary Parenchyma
Since its inception in the mid-1970s, computed tomography has played a major role in the evaluation of the mediastinum and to a lesser extent in that of the chest wall and pleura. Adequate evaluations of the pulmonary parenchyma were not possible until the early 1980s, when achievement of short scanning times permitted studies at suspended respiration. In addition, thinner slice sections and higher spatial resolution techniques enabled more detailed analyses of the parenchyma, providing a wealth of new data. Over the past few years, the rapid spread and ready availability of CT scanners has led to a dramatic increase in the use of CT in pulmonary parenchymal pathology, providing an opportunity to better evaluate its current and potential future role. More info
CT in the Evaluation of Focal Pulmonary Pathology
Staging of bronchogenic carcinoma was one of the earliest applications of CT in localized lung disease. Initially, high hopes were placed on the ability of CT to precisely display the relationships of a tumor mass to the pleura and surrounding structures and thus reliably define local invasion. However, it soon became clear that CT was not as accurate as expected. Error rate was particularly high when only minor changes such as thickening of the pleura or minor irregularities of the tumor-pleura interface were observed. Associated inflammatory changes or desmoplastic reactions may easily simulate minor degrees of invasion. Only when clear destruction or gross interdigitation of the tumor with surrounding structures is present can one be certain of tumor invasion. Further, the surgical management of locally invasive carcinoma has become more effective and unless a major structure such as a large vessel, the trachea, the esophagus or a vertebral body is involved, attempts at curative resection are still technically possible. Precise localization of the tumor for surgical planning is very effective with CT. Ambiguous sites of localization such as superior segments of the lower lobes vs upper lobes can almost always be clarified by demonstrating the fissures with thin-section CT scans. CT localization of a tumor in relation to airways down to the subsegmental bronchi is reliable, thus offering effective guidance for bron-choscopic tissue sampling.