Xeroradiography

Xeroradiography is a type of x-ray in which a picture of the body is recorded on paper rather than on film. In this technique, a plate of selenium, which rests on a thin layer of aluminium oxide, is charged uniformly by passing it in front of a '[http://www.medcyclopaedia.com/library/topics/volume_i/s/scorotron.aspx scorotron]'. As X-ray photon impinges on this amorphous coat of selenium, charges diffuse out, in proportion to energy content of the X-ray. This occurs as a result of [http://en.wiktionary.org/wiki/photoconduction photoconduction]. The resulting imprint, in the form of charge distribution on the plate, attracts toner particles, which is then transferred to reusable paper plates. In contrast to conventional X-rays, photographic developers are not needed. Hence the term xeroradiography; 'xero' meaning dry in Greek. It requires more radiation exposure. Its use is in mammography.