![]() The PSP electrons are energized when exposed to x-rays and form the latent image. The IP is not linked directly to a computer. Whereas x-ray film and intensifying screens are housed in a cassette, the PSP screen is housed in what is called an imaging plate (IP). The PSPs are incorporated into a storage phosphor screen. The capture element is a photostimulable storage phosphor, barium fluorohalide with europium. Although several newer DR detector systems have become available, CR will more than likely prevail for several years to come. The initial investment also is less expensive compared to the remaining DR systems, which may also require retrofitting of existing x-ray equipment (in particular, the orthoposer). Photostimulable Storage Phosphor DetectorsĪlso known as computed radiography (CR), the PSP detector is widely used in podiatric settings because it has been available the longest. However, the emphasis is on application to podiatric radiology. The descriptions of the various technologies below are generic, since there is constant development of new and improved devices. The DR field is growing and changing rapidly. Computer algorithms convert the digital data into a digital image that is then viewed on a monitor. The collection element sends an electric signal to an analog-to-digital converter (ADC), which then goes to a computer that has appropriate software installed. The element that collects the x-ray–generated signal may be a photodetector, CCD camera, thin-film transistor (TFT) array, or CMOS. The signal generated by the capture element is transferred or coupled to the collecting element via an optical system, photodiode, or a photoconductor. The x-ray may be captured by a photostimulable phosphor, scintillation phosphor, or a photoconductor. Each has three components: the capture element, coupling element, and collection element. We have found it useful to categorize by the type of detector system, but will include reference to the other categorizations when appropriate.įour DR detector systems are available for podiatric use: the photostimulable storage phosphor (PSP) detector, charge-coupled device (CCD) detector, complementary metal-oxide semiconductor (CMOS) detector, and flat-panel detector (FPD). direct), and linkage to computer (indirect vs. longer), x-ray signal conversion (indirect vs. ![]() no cassette), image acquisition time (immediate vs. They have been categorized by form factor (cassette-based vs. These factors are discussed in detail in Chapter 2.Īttempts have been made to categorize the different types of DR. ![]() Furthermore, the four quality factors that the limited x-ray machine operator (LXMO) controls before the x-ray beam strikes the image receptor, radiographic density, contrast, recorded detail, and distortion, apply to DR as well. No matter what image acquisition system is used to process the image, however, they all depend on the same x-ray machine. These images are then stored electronically. The latent image formed on the electronic detector is measured and converted into an analog electrical signal that is then converted into a digital signal, which is processed by a computer, creating a digital image that is viewed on a monitor. With the advent of filmless or digital radiography (DR) in the late 20th century, an electronic detector has replaced the film–screen image receptor. The exposed film must be processed with chemicals to produce the manifest image, which is then viewed on a light box, cataloged, and physically stored. Conventional radiography has, for more than 100 years, employed as an image receptor the film–intensifying screen combination. The visible (manifest) radiographic image is produced following processing of the latent image. X-rays interact with an image receptor and form the latent image (an invisible change that represents the object that was radiographed) after passing through the patient. ![]()
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