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US6042986A Portal localization radiographic element and method of imaging 失效
门静脉定位放射照相元件和成像方法

Portal localization radiographic element and method of imaging
Abstract:
Portal localization radiographic elements and a process of confirming the targeting of a beam of X-radiation of from 4 to 25 MVp using the portal radiographic elements are disclosed. The X-radiation is directed at a subject containing features that are identifiable by differing levels of X-radiation absorption. After a first X-radiation exposure a shield containing a portal is placed between the subject and the source of X-radiation. X-radiation is directed at the subject through the portal. In each instance the X-radiation leaving the subject impinges on a metal screen, causing it to emit electrons, and the electrons impinge upon a fluorescent screen, causing it to emit light, creating during the first and second exposures first and second superimposed latent images in the radiographic element. A processor is employed to convert the latent images to viewable silver images from which intended targeting of the X-radiation passing through the portal in relation to the identifiable features of the subject is realized. The processor relies on attenuation of an infrared beam of a wavelength from 850 to 1100 nm by the radiographic element for activation, and at least one of the hydrophilic colloid layers of the radiographic element contains particles having an index of refraction in the wavelength range of from 850 to 1100 nm that differs from that of the hydrophilic colloid by at least 0.2 to create a specular density capable of attenuating the infrared beam and activating the processor.
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