Electrostatic imaging in radiology: limitations and prospects

Abstract

In this radiographic technique, the latent image takes the form of a surface distribution of electric charge which may be rendered visible in various ways. The charge distribution is formed either on a selenium surface (xeroradiography) or by collecting ions on an insulating foil (ionography). Conventional powder development techniques yield visible images in which high spatial frequencies are enhanced (‘edge contrast’) and low frequencies largely suppressed. This contrast pattern is useful for the radiological study of soft tissues, vascular structure, bones and joints. Xeroradiography is less sensitive than film-screen radiography and this restricts its medical application to sites where gonad exposure is minimal. Ionography with compressed xenon has high sensitivity but is not yet fully developed commercially. It requires a rigid link between the X-ray tube and the recording chamber. The latent image is produced on plastic foil which can then be developed in many different ways to yield either edge contrast or density images. Liquid ionography avoids the need for high pressure and allows multiple copies of the latent image to be made. There are some special applications of ionography in the research laboratory but in industrial work xeroradiography, despite lower sensitivity, is likely to be more convenient for any applications which demand edge contrast pictures.