DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS

1. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS Without reference, identify principles relating to Digital Radiography Clinical Applications with at least 70 percent accuracy.

2. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Any technology that will be used to capture projection radiographic images must do three things well: • Interact with x-ray quanta (absorb) • Produce and retain (sufficiently long) a latent image • Convert the latent image into a visible image or a digital image • Three major capture technologies • Screen/Film Radiography • Computed Radiography using Storage Phosphors Plates • Digital Radiography • Two approaches to digital radiography • Direct Detectors • A conversion detector that uses an X-ray semiconductor material that holds an electrical charge to convert x-ray quanta directly into an electrical charge • Quanta - A quantity or amount of x-rays • The semiconductor material can be coated as a thin layer on a flat panel or a large drum

3. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS

4. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Indirect Detectors • An x-ray absorbing Scintillator emits light that can be measured with either a Charged Coupled Device (CCD) or a Thin Film Diode (TFC) array • Scintillator: A detector that is made of a substance that glows when hit by high-energy particles or photons • With CCD's, light coming out of the scintillator is optically coupled to the much smaller surface of the CCD detector • This requires de-magnification of the aerial image • Improvements in x-ray detector technology • It is expected that digital radiography image quality will exceed that of storage phosphor technology (CR) and screen/film (regular radiographic x-ray film) systems • Additionally, DR's immediate access to images promises vast improvements in productivity and workflow • Approaches to Digital Radiography • The heart of a digital radiography system is the detector • Indirect digital radiography systems use light as an intermediate to perform the necessary work

5. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • A scintillation material such as cesium can be used to absorb x-rays and produce light required to form the image • An array of TFD's (Thin Film Diode) is used to convert this light into an electrical charge that can be measured by an array of TFT's (Thin Film Transistors) • Another approach to indirect digital radiography uses Scintillators and small CCD detectors instead of large flat-panels • These CCD's (Charged Coupled Devices) are the same ones found in today's electronic cameras • Because of the small size of the CCD's compared to the anatomical objects, some means must be included to reduce the size of the aerial image to match the CCD light detector • In some systems an image intensifier tube, like the ones used in dynamic imaging, performs this task • Direct flat-panel radiography systems: • Do not use light as an intermediate signal • The absorption of x-rays generates a charge, which is measured directly by the TFT array • The electronic sandwich for a direct flat-panel digital radiography detector, is similar to that of the indirect detector, except that there is no light detection layer

6. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Another approach to direct digital radiography uses a rotating drum instead of a flat-panel • The drum is coated with an amorphous selenium layer, and has a high voltage across it • Exposure to x-rays creates a latent charge image on the surface of the drum which can be measured using an array of tiny electrometer probes that ride over its surface • System Components • Control and read-out electronics • Computer interface software • X-ray machine communications and synchronization • Image Buffer • Image processing software • Computer Interface Software • The latent image on the flat-panel array must be read-out and converted to a digital image • In order to do this, a control system is used that allows each line of the flat-panel array to be read out sequentially • These signals are amplified, quantized, and stored in local memory

7. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • This process is driven by a host computer that is interfaced to various components of the system • The flat-panel array must be made ready for each x-ray exposure and there must be synchronization between the x-ray equipment and the detector • This is also accomplished through the host computer • The digital data we generate have to be stored somewhere • As in CR, this storage function is usually distributed across various components of the system • The capacity of the buffers must be calculated to match the anticipated use of the system, which includes: • Image throughput • Network load • Redundancy • The availability of remote storage, etc • As with any digital imaging system, image processing must be used to prepare the image for display • However, image processing also plays an important role during the acquisition step • In particular, image processing must be used to correct for the characteristics of the flat-panel array

8. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • For example • Variations between sensing elements • Variations in gain or amplification from line to line is created • Signal shifts from line to line must all be corrected before the final raw digital image is created • Chain of events during the acquisition of a digital radiography image • With Direct Digital Radiography • Incident x-rays are absorbed by the semiconductor layer • Converted directly into latent charge image on the sensing elements of the flat-panel array • This latent image can be read-out or converted into an analog electrical signal • Digitized: This digital image can be manipulated with image processing to produce other "looks" that can be sent to an output device to be converted into a visible image again • Radiographic Technique • mAs controls dose to the patient • mAs does not control the overall lightness or darkness of the output image • Image processing controls lightness and darkness

9. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Computed Radiography (CR) Plate Reader • Step Overview • Computed Radiography • CR Plate Reader Systems • Computed Radiography • Computed radiography (CR) is a process for capturing digital radiographic images • Computed radiography may be used anywhere x-ray film is used • CR enables replacement of film and film processing and produces a high quality digital image • CR can save money otherwise spent on film and chemicals • CR can also help manage images electronically--eliminating the need for film jackets, file rooms, and slow film retrievals • CR uses your existing x-ray equipment and, like a film processor, one CR system can support multiple x-ray rooms • Computed radiography is sometimes confused with digital radiography, or DR • DR produces digital images like CR, but because of the integrated detection system, it requires the replacement of the entire x-ray system • CR workflow is very similar to conventional film processing

10. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Instead of taking the film cassette to a film processor, the technologist takes a plate to the CR reader • The time required to generate a digital image is similar to processing a piece of film • For exposure, place a storage phosphor plate in a cassette instead of a piece of film • The phosphor plate captures and "stores" the x-rays • "Develop" the image in a CR reader instead of a film processor • The CR reader extracts the information stored in the plate and produces a digital image • A digital image acquisition process produces images equivalent to conventional x-ray film-screen systems • CR Plate Reader Systems are made up of Storage Phosphor Plates, the CR Reader, and the CR Acquisition Station • Storage phosphor plates • Storage phosphor plates look like the intensifying screens found in conventional film-screen cassettes • Instead of emitting light immediately when exposed to x-rays, they have the special property of storing the x-ray energy in a latent image • The CR reader releases the latent image

11. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Storage phosphors also are unique because they respond to a very wide range of x-ray exposures • This latitude gives you flexibility in selecting x-ray technique without worrying about under or over exposure • Regardless of the exposure, the image will display correctly • This drastically reduces retakes due to inappropriate exposure • Regardless of the exposure, the image can be displayed correctly • The storage phosphor plate fits inside a standard film cassette and the exposure to x-rays is exactly like film • The plate stores the x-rays • The life of a phosphor plate depends on its careful handling • Physical damage to the plate will limit its useful life • The chemistry of the phosphors does not degrade after repeated exposures • If properly cared for, a plate will produce thousands of images

12. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • CR Reader • A high power laser scans the plate after its insertion into the CR reader • The laser light causes the storage phosphors to release the captured energy • In the CR reader this energy is converted into a digital image • After exposure and scanning, the phosphor plate is "erased" by exposing it to bright light • After the removal of the previous image stored in the phosphors, the plate is ready for another exposure • Upon receipt, a CR acquisition station views, manipulates, stores, and prints the digital image • CR acquisition station • Viewing images • The CR acquisition station sends digital images to diagnostic or review stations • Generally, these are PC-based and easy to use • Quite a few vendors offer these viewers for placement in locations such as the radiology department, ICU, CCU, ER, and basically anywhere you need access to the images • Some CR readers have a high quality grayscale monitor directly on the unit

13. DIGITAL RADIOGRAPHY CLINICAL APPLICATIONS • Image manipulation • This capability allows image characteristic changes such as viewing and detecting anomalies in dark or light areas of the film, highlight certain structures, enhance edges, change brightness and contrast, and so on • Image manipulation functions are all but impossible with traditional film and light boxes • Storing images • Because CR eliminates film by generating digital images, the images must be stored electronically • Depending on your infrastructure, images can be stored on a large, automatic, digital archive connected to the network, on tape libraries, or on disks • The desktop CR can access network archives as well as archive images locally on a single workstation • Printing images - To create hard copies of digital images produced by a CR system; send them to a laser printer or multi-format camera