55 degrees oblique hilar tomography.

Fifty-five-degree oblique hilar tomography is an accurate and simple means of evaluating hilar anatomy and pathology. It is of most value in proving the hilum to be normal in cases in which plain chest roentgenograms suggest a hilar lesion. It is accurate in differentiating hilar adenopathy from hilar masses and in both of these it is helpful in determining the extent and bilaterality of the disease process. Unfortunately, granulomatous infiltrates within the hilum cannot be differentiated from tumor. The procedure is of limited value in the presence of diffuse perihilar pulmonary fibrosis, and at this time caution must be advised in the interpretation of small, unilateral, ill-defined hilar densities as tumors.