Over the past two decades CR, or computed radiography, has dramatically changed how everyone from small general practitioners to large hospitals thinks about x-ray. At its core, CR is the digital heir to traditional, film based x-ray development. It takes advantage of existing, low-cost x-ray equipment and combines it with all of the advantages of digital radiology.
CR technology uses a cassette that is similar to conventional radiography except that it contains no film and needs no chemicals or dark rooms to develop. Instead, there is a reusable phosphor plate inside of each cassette that is digitally scanned by a plate reader and displayed on a computer monitor. Advantages of this technology include cost, speed, ease of distribution and storage, and flexibility with existing or low-cost x-ray equipment. In addition, CR systems rarely requires any construction and can be implemented in a day.
The bottom line with CR is that it provides a relatively inexpensive way for new and existing practices, hospitals and other care providers to take advantage of the digital radiology revolution. A large variety of companies make computed radiography systems that can fit almost any budget and volume requirements.
How Does CR Work?
In many ways, CR is similar to traditional, film based radiography, but the key difference is that the process is digital. You begin by taking an x-ray onto a cassette, much the same as you would normally. That cassette is then inserted into a machine often referred to as a CR reader. The reader scans the plate inside of the cassette digitally and displays the resulting digital image on a screen for viewing and manipulation. The process is as simple as shoot, scan and read. Generally with any CR system there are four key components that discussed below.
First, there is the x-ray emitting equipment. Facilities with existing film based x-ray can take advantage of their previous investment in equipment. There is no need to replace the tubes, generators or any other component. Even familiar techniques often do not need to be replaced. New facilities or ones that previously had no x-ray can take advantage of the low-cost, competitive market for new and used x-ray equipment.
The cassettes look and function in a similar way to film cassettes, but they contain a reusable phosphor plate instead of traditional film. The number of times that each phosphor plate can be used can range from the multiple thousands to well more than ten thousand x-rays. The cassettes rarely need to be opened therefore prolonging both the life of the cassette and the plate. Cassettes come in a wide variety of standard and specialized sizes. The most common, 10”x12” and 14”x17”, are available from most CR manufacturers and fit into existing wall and table buckeys and can be used on table tops.
Replacing the traditional chemical developer is a digital computed radiography reader. The basic function of the reader is to remove and scan the phosphor plate from the cassette. The majority of CR readers also erase and reinsert the plate into the cassette at the end of the process. The speed of the scan and the number of cassettes that can be inserted simultaneously may be an important factor in determining which brand and model to select. They also come in a variety of shapes and sizes and can be placed in vehicles, on mobile carts, mounted to the wall, placed on a table or sit on the floor. Because they don’t need to be located in a specific location, such as a dark room, placement of CR readers is extremely flexible.
The scanned images are then available on the acquisition workstation. These workstations are frequently standard PCs with specialized software. The images can be viewed, manipulated and sent from these workstations. The exact features of the software on the workstation vary from model to model, but most of them allow for viewing and manipulation by the technologists and doctors. Often the software is very simple to use and is easily learned by technologists trained exclusively on film.
CR systems have dropped significantly in price in the last several years. They now start as low as $20,000 for basic models and go up from there. Each make and model has different features and addresses a different niche. The features and speed of CR systems determine the price.