A Study of the Roentgenologic Appearance of the Lobes of the Lung and the Interlobar Fissures

Abstract

ROENTGENOGRAMS consist of superimposed shadows of a three-dimension object projected on a flat plane. The shadows obtained on the film are of two dimensions and do not give a true picture of the shape of the process or its location. To bring out the third dimension, stereo-roentgenograms are often taken. The use of postero-anterior and lateral projections gives us two films in planes at right-angles to each other, which is of great aid in studying the position and shape of the parts under consideration. The necessity of knowing the exact position and shape of a disease process is especially important in the chest. Processes occurring in the interlobar septa offer particular difficulty in interpretation on a single postero-anterior projection. Because of the oblique position of the septa, the horizontal ray projects the shadow of the septa on the roentgenogram as a broad surface, giving the impression of a diffuse area of lung involvement. Stereo-roentgenograms do not bring out the true nature or location of this process. A lateral view, in the same plane as the interlobar fissure, gives us a totally different conception as to the limits of the process. No longer should roentgenologists be satisfied to make a diagnosis of shadows of increased density occupying the upper or lower part of the chest. With the demand for information made by the chest surgeon, roentgenologists are called upon to be more accurate in locating the disease process, as well as to be more specific regarding its nature. Considerable literature has appeared concerning the roentgenologic appearance of certain disease processes, but there is no satisfactory study available as a guide to the exact appearance on the roentgenogram of the lobes of the lung and the interlobar septa. This study was undertaken to provide such a set of diagrams, showing the appearance of the lobes of the lung and interlobar septa in the postero-anterior and lateral views. The shadows obtained were subsequently compared to clinical cases of unquestioned diagnoses. We do not mean to imply that all disease processes affecting these divisions of the lung would occupy the areas designated in the diagrams: previous disease conditions of the lung may have resulted in retraction, distortion, or displacement of the region of the lung under consideration. The entire interlober septum may not be, and usually is not, involved by the disease process. Likewise, only a portion of one or more lobes may be affected. Notwithstanding such factors which may play a part in the distortion of these shadows, the general configuration of the affected parts of the lung closely simulate the diagrams experimentally produced. In a previous article one of us described the roentgenologic appearance of the potential interlobar spaces. The present study is a continuation of the subject, illustrating the affected spaces by clinical cases.