Flat-panel detectors are more sensitive and faster than film. Their sensitivity allows a lower dose of radiation for a given picture quality than film. For fluoroscopy, they are lighter, far more durable, smaller in volume, more accurate, and have much less image distortion than x-ray image intensifiers and can also be produced with larger areas. Disadvantages compared toIIs can include defective image elements, higher costs and lower spatial resolution.
In general radiography, there are time and cost savings to be made over computed radiography and (especially) film systems. In the United States, digital radiography is on course to surpass use of computed radiography and film.
In mammography, direct conversion FPDs have been shown to outperform film and indirect technologies in terms of resolution citation needed, signal-to-noise ratio, and quantum efficiency. Digital mammography is commonly recommended as the minimum standard for breast screening programmes.
Why Direct FPD???
Direct conversion imagers utilize photoconductors, such as amorphous selenium (a-Se), to capture and convert incident x-ray photons directly into electric charge. X-ray photons incident upon a layer of a-Se generate electron-hole pairs via the internal photoelectric effect. A bias voltage applied to the depth of the selenium layer draw the electrons and holes to corresponding electrodes; the generated current is thus proportional to the intensity of the irradiation. Signal is then read out using underlying readout electronics, typically by a thin-film transistor (TFT) array.
By eliminating the optical conversion step inherent to indirect conversion detectors, lateral spread of optical photons is eliminated, thus reducing blur in the resulting signal profile in direct conversion detectors. Coupled with the small pixel sizes achievable with TFT technology, a-Se direct conversion detectors can thus provide high spatial resolution. This high spatial
resolution, coupled with a-Se's relative high quantum detection efficiency for low energy photons (< 30 keV), motivate the use of this detector configuration for mammography, in which high resolution is desirable to identify microcalcifications.