The roentgenologic study of the diaphragm appears to have been confined chiefly to the anteroposterior view of the thorax. This would suffice, provided the surface of the diaphragm would remain on the same level through its whole extent; but such is not the case. The diaphragm slopes downward in its course from before backward. Thus a good deal of the posterior half of the diaphragm remains obscured from view. In order to make the whole of the diaphragm accessible to exploration, it became quite evident that a lateral view of the thorax should supplement the usual anteroposterior view. Having studied a large number of diaphragms in the two positions, I became quite convinced of their true value in recognizing abnormal conditions with greater accuracy than it was possible by the use of one position alone.
ROENTGEN ANATOMY OF THE DIAPHRAGM
In the anteroposterior view of the thorax (fig. 1 A
BROWN S. THE ROENTGENOLOGIC STUDY OF THE DIAPHRAGM. JAMA. 1931;97(10):678-681. doi:10.1001/jama.1931.02730100002002