The phosphor layer overlays the reflective layer, which reflects the light back to the film and both are coated onto a firm plastic base. Screens have a crystalline phosphor layer that produces visible light when exposed to x-rays. Cassette holders are rigid or flexible configurations with intensifying screens on the internal walls. Since the film does not have protective outer wrappings, it must be housed in a cassette holder during exposure. The film is either 5” or 6” x 12” (15 x 30 cm) in size. However, the image quality regardless of receptor remains dependent upon proper patient preparation, patient positioning and exposure selection to produce optimal results and to avoid retakes.įilm used for panoramic radiography is more sensitive and packaged differently than intraoral film. density, contrast, measurement, image reversal manipulations) and teleradiography capabilities for the purposes of consultation, insurance, or referral. Other advantages include timesaving, electronic image storage and transfer, the ability to enhance the captured image with various tools (e.g. The obvious advantage of digital panoramic imaging, particularly direct digital panoramic imaging, is elimination of the darkroom including machine cleaning and maintenance, chemical handling, and solution change as well as associated processing errors. 8, 9 PSP imaging is considered an indirect digital imaging method because the data is captured in an analog format like film and then converted into digital data via the scanning process. It is important to scan the exposed plate without delay as white light or delayed scanning can degrade the result. Recent developments include faster plate scanning and erasure of the plate during the scanning process. PSP plates are reusable but must be exposed to light to erase remnant energy. 8 The emitted light is captured, intensified by a photomultiplier tube and converted into digital data. When a helium-neon laser beam scans the PSP plate, the energy is released in the form of blue florescent light. The image is captured on the phosphor plate and the energy is stored on the plate until it released during a laser scanning process. A PSP plate is inserted into a cassette just like film but without the intensifying screens. PSP sensors consist of a rare earth phosphor, barium europium fluorohalide, coated onto a polyester base. The acquired images can be viewed in diverse ways through the application of software enhancement tools. The image is archived in the patient database. Then, the image is displayed on the computer monitor in real time. The computer processes the image as it is acquired. The patient is aligned in the same head positions as required in film-based panoramic x-ray machines. To initiate the process, a patient file must be created in the computer software system. In the subsequent photographs, a CCD sensor system is used to capture the image. The vertical sensor is moved around the patient opposite to the x-ray source and captures the image one vertical line at a time. 2, 8 Both types of digital image receptors and film will produce diagnostic results when properly utilized.ĬCD/CMOS linear array designs arrange the detector in a grid with the same vertical dimension as panoramic film but only a few pixels wide. The digital panoramic imaging method is comparable to conventional panoramic radiography but the receptor, processing, display, storage and transmission capabilities differ from film-based imaging. CCD/CMOS and PSP receptors are used for intraoral radiography as well but with altered sizes and receptor designs. Panoramic x-ray systems are available that use either linear array charge-coupled device (CCD) or complementary metal oxide semi-conductor (CMOS) detectors as well as photostimulable phosphor plate (PSP) receptors.
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