X-ray film of chest demonstrating over penetration
Radiography is essential to diagnosing many diseases and pathology that might be presented to a doctor's office. Many tests and procedures are included under the radiology umbrella, but regular radiography is the oldest and most used diagnostic tool in this field. Also known as X-Rays, these radiographic views can be taken by two main technologies. The first and oldest technology is film radiography, while the newer radiographic choice is digital radiography.
History
Wilhelm Conrad Roentgen discovered a new wavelength or "ray" in 1895. Not knowing the properties of these rays, he aptly called them X-rays. This accidental finding during a routine experiment has been the foundation of medical radiography. Advancements were swift and have increased over time. For the next 85 years, developments were based on an x-ray film and screen combinations. X-rays were taken on these films and processed in chemicals to produce an image. In the May-June 2007 issue of "Radiographics," Markus Korner et al. note two new ways of acquiring images and when they were introduced. In 1980, Computed Radiography (CR) was first used, and in 1994 Direct Digital Radiography (DR) was introduced. Both of these are considered to be digital radiography.
Similarities
The two ways to obtain an X-ray image have similarities. They each require an X-ray exposure to create an image. Computed Radiography (CR) is similar to Film Radiography or conventional radiography in that it requires a cassette and uses the same radiographic equipment used for conventional radiography. They are also comparable because once the image is captured in the cassette further processing is required to view the images. Direct Digital Radiography (DR) and Computed Radiography compare in that they both are able to acquire images in seconds and both create a digital image that can be viewed on virtually any computer.
Differences
Computed Radiography (CR) and Film Radiography are different in several important ways. First, CR uses a photostimulable phosphor plate within the cassette, versus the emulsion-gelatin film for conventional radiography. Secondly, to process the image in conventional radiography the film has to be removed from the cassette in a darkroom so that no light can expose the film, and the film is then run through a processor to receive the hard-copy image. In CR, the cassette is placed in a "reader" that digitizes the image onto a computer screen. This is known as a soft-copy image. With DR, no cassette is needed, as the image is directly captured on a flat plate reader and seen within seconds on a monitor, to be accepted or deleted.
Digital Advantages
Digital Radiography offers many advantages over Film Radiography. The most important advantage is an overall decrease of radiation dose to the patient in most cases. Even if a patient is over-exposed, the image will usually turn out good or can be manipulated to look good so another exposure is not needed. With digital films, the images can be seen quickly and stored digitally. Digital images also have many post-processing techniques that can be used to make the image diagnostically better. For digital images a darkroom is no longer necessary and the chemicals used in the processor are not needed.
Digital Disadvantages
There are not many disadvantages of digital radiography over conventional radiography, but cost is a big factor. Digital radiography systems cost more to set up and are more expensive to replace if parts go bad. Another disadvantage is that it is possible for a technologist to routinely over-expose patients, knowing the image will turn out good versus what the image would look like if it was under-exposed. However, this disadvantage can be lessened by good quality assurance programs and following the manufacturer's recommended exposure index or sensitivity number.
Tags: conventional radiography, Computed Radiography, Digital Radiography, Film Radiography, digital radiography, Direct Digital, Direct Digital Radiography
