Visibility and sharpness of lung structure at 90, 140, and 350 kV

Human lung specimens containing a variety of lesions were radiographed at 90, 140, and 350 kV. Nodules less than 3 mm in diameter and linear shadows less than 0.3 mm in diameter were either not visible or poorly seen at 350 kV. Larger lesions were seen well with all three kilovoltages, although the interfaces were more distinct on the 90- and 140-kV views. The best images were obtained at 90, slightly worse at 140, and least satisfactory at 350 kV; in general, however, most features of the normal and diseased lung were readily seen at all three kilovoltages. The apparent degradation of the lung image at high kV levels may be explained by the large focal spot of the 350-kV system and the attenuation properties of high-energy photons.