Akademik

A technique used to enhance detectability of opacified anatomic structures on radiographic or scintigraphic images; a negative of an image made before introduction of contrast medium or radionuclide is photographically or electronically removed from a later image; commonly used in cerebral angiography. SEE ALSO: digital s. angiography, mask.

- energy s. digital radiography using higher- and lower-energy exposures, either by double exposure at 2-kV levels or by interposing a copper filter that absorbs the lower-energy photons between two phosphor plates, with computer calculation of high-Z and low-Z images (bone and soft tissues, respectively); makes use of the fact that lower-energy x-rays are absorbed by more high-Z substances, such as calcium and copper, because of the photoelectric effect. SEE ALSO: Z, photoelectric effect, phosphor plate.