Digital radiography is a more advanced form of x-ray imaging than conventional film radiography. It uses digital radiography sensors, instead of X‐ray film, to capture data during the inspection process and send them to a computer for processing. Digital radiography produces high-quality images that are stored on computer files rather than physical films. These images can then be archived, shared, and studied easily without any need for chemicals or special storage processes.
Digital radiography has found applications in a wide variety of fields. Its greatest use is in medicine, where the diagnostic abilities of radiography are used to aid in the early detection and treatment of disease.
Since digital radiography uses image capturing devices to transform radiation photons into useful information, it can be utilized in three main ways. The first is standard digital radiography which involves a single detector that is able to expose an image on the basis of stored data like in any other digital camera. The second is digital radiography with the use of image intensifiers or image intensifier tubes. In this type of system, the image intensifiers are used to convert photons into useful signals. Finally, there is panoramic imaging which produces an exposed film from a set of detector elements that cover more than one plane.
The process of digital detection starts with X-ray energy. When this energy hits the detector, it becomes an electrical charge that can be converted into a grayscale image. This helps us understand how much x-ray energy is absorbed in each point of image.
The image is then processed using the appropriate software, which reduces camera noise and sharpens the image. Other adjustments include color correction and contrast enhancement.
Digital images are stored on various types of computer hard drives or storage media for viewing on a computer. They can be enlarged, measured, and manipulated while being studied. They can also be sent to other computers or linked to digital record systems.
X-ray detectors convert X-ray photons to electrons via phosphor or scintillator material. The amount of charge collected at the interface of the materials is proportional to the number of x-ray photons striking the detector. These images are turned into digital information and displayed on a computer monitor.
Flat Panel Detectors
Flat-panel detectors, commonly known as solid-state detectors, convert high-energy X-rays to electrical signals and are used in digital radiography systems. Direct and indirect conversion type flat-panel detectors are available to meet different radiation levels and system configurations.
Direct-conversion flat panel detectors use a selenium TFT array to absorb and store electrical charges. These devices have a high spatial resolution, thereby decreasing radiation dosage compared to conventional X-ray machines. Furthermore, these detectors eliminate the need to worry about proper exposure or underexposure.
An indirect conversion flat panel detector commonly used in a system of direct digital radiography is called a charge-coupled device (CCD). The CCD functions as a light-sensitive sensor, similar to that of a camera. One drawback of these devices, however, is that they are limited in size to about 5 cm2. A charge-coupled device uses a combination of a phosphor and an X-ray detector to convert X-rays to light. The light is focused on a CCD, which converts the rays into electrical charges. These electrical charges are then passed to a thin-film transistor array for data output.
Computed radiography, also called CR or rad–x, is a type of imaging that captures an image dynamically on a phosphor plate in a cassette that can easily be connected to a computer. It is commonly used as a bridging technology between traditional film-based X-ray equipment and the increasingly popular digital methods.
Computed Radiography (CR) produces images which are nearly identical to conventional radiograph images and as such requires little change to your office or workflow. It is the most cost-effective choice for X-ray imaging. The positive aspects of CR systems are largely overshadowed by the potential setbacks or deficiencies they may have. CR cassettes can be susceptible to damage and may require frequent replacement, but they tend to be less expensive than wireless DR panels.
Advantages of Digital Radiography
- Digital radiography is used for diagnostic radiology. It offers extraordinarily high image quality, which is enhanced by the rapid processing of images, resulting in a quick diagnosis and treatment. Digital imaging also allows patients to access their health information and store it remotely.
- Detectors can be described in terms of efficiency. DQE stands for detection quantum efficiency and tells you how well a detector turns an X-ray photon into an electrical signal. A detection quantum efficiency of 100 percent means that no X-ray photons are lost, and there is no detectable noise added to the X-ray signal. Digital radiography systems typically yield DQE values of 65%. This is considerably higher than the typical 30% measured with computerized radiography. The advantage of digital imaging is the ability to use lower radiation doses without compromising image quality.
Disadvantages of Digital Radiography
- Digital radiography has a cost disadvantage; for each position of the Bucky’s detectors, two separate detector plates will be needed.
- Furthermore, they cannot be imaged from most angles. To address this issue, new designs have been developed to increase the usability of this method.
- Another problem is the need for high brightness in monitors to view final digital images and the need for large amounts of high-resolution digital storage to organize and store data.
- The high-resolution images produced by digital radiography require a large amount of data storage, making it imperative that hospitals have high-speed networks to support them.
Digital radiography, or DR, is now firmly established in medical practice and will remain so for years to come. Physicians who remain open to this technology will be better equipped to meet the needs of their patients. The technology, practices, and systems involved in digital radiography have matured and can be trusted as reliable methods of patient care.