200 kV xeroradiography in occupational exposure to silica and asbestos.

Some details of the physics of xeroradiography, and the bearing these have on films of the lung obtained by this technique, are discussed. In experiments designed to obtain useful films with a minimum of radiation exposure it was found that an exposure range of 10-30 mas at 200 kV at 1.35 m (4 1/2 ft) without a grid or air gap gave very satisfactory results. The positive model of development was considered to give more information than the negative mode. One hundred and fourteen miners who had been exposed to silica dust, asbestos dusts or both, were examined by this technique. The xeroradiographs were compared with silver halide films taken at 200 kV. The xeroradiographs were considered to be superior in several respects, especially in the delineation of vascular shadows, normal and abnormal linear opacities. Linear opacities in asbestos-exposed subjects were better shown on the xeroradiographs and were occasionally seen on these films when the 200 kV conventional film was entirely normal. Small rounded opacities of silicosis were very poorly shown on the xeroradiographs. Pleural thickening and pleural plaques may be very well demonstrated.