Fluoreszenzradiographie - Fluoreszenzradiographie

The Fluoreszenzradiographie is an imaging X-ray methods .

Technical principle

With the classic X-ray image, a film is blackened by X-rays . As a result, objects that are X-ray transparent ( air or clear liquids ) are depicted blackish and X-ray opaque objects are depicted whitish. (However, this weighting is also dependent on the fixing method used during image development.)

In contrast to this, fluorescence radiography uses a fluorescence effect that arises when X-rays strike a corresponding luminous medium.

story

In the first half of the 20th century, fluorescence radiography (the classic "fluorescent screen") enjoyed great popularity because it made real-time images possible. In contrast, film-based X-ray processes required developing the images, which took a considerable amount of time. Smaller orthopedic and gastroenterological medical practices could save themselves a photo laboratory and staff.

However, with increasing awareness of radiation hygiene, these fluoroscopic methods came under more and more criticism, since the radiation dose was high and the threshold for use was very low.

The process was ultimately obsolete in many areas due to automated and very fast film development and the obligation to document .

Modern technical application

Today, fluorescence radiographic techniques can be found in many areas of current X-ray procedures. For example, a so-called intensifying screen is integrated behind the X-ray film in a current recording device . [1] When X-rays pass through the film and expose it, it hits this intensifying screen in the continued beam path and causes it to glow. The emitted light can then expose the film and thus make better use of the X-rays used. It must also be mentioned that classic silver nitrateFilms can only really use certain X-ray spectra for imaging, but the intensifying screen can also make other spectra accessible for imaging. The disadvantage, however, is that the film is occasionally overexposed by the intensifying screen and the images tend to be blurred.

This technology is also used in image converters (also called BV for image intensifiers ). The problem is that X-rays cannot be electronically recorded directly. X-ray cameras are accordingly a grid of small fluorescent fields with a photocell directly on top . When X-rays hit such a field, it is excited to glow and the photocell on top of it emits an electrical current. Since this signal can in turn be amplified electronically, the term image intensifier is also used for the image converter (conversion of a fluorescent image into an electronic image). Modern image converters work with pulsed images. The radiation dose is delivered in single pulses. When calculating the monitor imageHDR effects can then be brought into play, in which summation effects still enable contrast in areas with high X-ray density , as well as automatically reducing the number of actually evaluated pulses in heavily overexposed areas. As a result, the image quality can be increased considerably or the radiation dose can be greatly reduced.

Individual evidence

  1. Beckelmann: Case Collection Radiology for MTRA