Over the past decade or so, advancements in detector technology and tube design have led to better image quality with lower radiation doses and reduced power usage. With all the advancements in the last decade or so, DR systems are fast catching up with CR Systems in Radiology departments. Is it time to go for Digital Radiography Systems instead of CR Systems?
CR Systems – Excellent alternative to Film based radiography
CR systems were introduced in the market in mid-1980’s.
CR Systems digitize X-ray images using a unique combination of photostimulable phosphor (PSP) plates and specialized scanners. When the PSP plate is exposed to X-ray radiation, it stores the energy released as light when scanned by a CR reader. This light is then converted into a digital image. CR systems hence offer a flexible, cost-effective solution for digitization, storage, retrieval, and analysis of X-ray imaging while enhancing the overall efficiency of the process as compared to film-based radiography. It was also less messy and cumbersome. The image quality was also comparable to film-based radiography.
In the last 2-3 decades, due to these advantages, CR Systems have largely replaced the dark rooms in hospitals and diagnostic centres all over the world.
However, CR Systems are now facing serious competition from DR Systems.
Emergence of Digital Radiography System
While CR Systems are well-established and entrenched technology over the last 3 decades, Digital radiography (DR) is relatively new, cutting-edge, revolutionary technology in the field of medical imaging.
Unlike CR systems that need an intermediate step of handling a phosphorus plate, DR systems capture X-ray images directly onto digital detectors and straightaway get displayed on a monitor. The detectors may be either flat-panel or charge-coupled devices (CCDs).
DR technology, offers significantly superior image quality, workflow efficiency, almost instantaneous image acquisition, lower radiation dosage and low maintenance hassle. Integrating images from DR systems with Electronic Medical Records is relatively easier too.
What Are the Differences Between Digital Radiography (DR) and Computed Radiography (CR) Systems?
The two systems can be compared across various parameters such as image acquisition process, image quality, workflow efficiency, radiation exposure, portability and cost & maintenance. Relative to CR Systems, DR systems have higher upfront costs but often lower long-term expenses due to reduced maintenance requirements and faster workflow efficiency. As a newer and cutting-edge technology, DR systems offer several benefit albeit at a cost premium.
CR systems are a well-established and widely used technology. Due to its long usage technicians today are very comfortable. Its low upfront cost, ample coverage of all types of procedures and adequate image quality makes it an easy choice even today. However, how long can you defer using new & superior technology?
Let’s examine how CR Systems and DR Systems compare on the following 10 key parameters in detail below:
| S.no. | Feature | CR | DR |
| 1 | Procedure Coverage | Depending on the area of examination and positioning required, in a CR we can use different cassettes sizes. This covers almost all type of procedures that need to be done with a set of cassettes. Most procedures can be done with a basic set of 3 cassette sizes (8”x10”, 10”x12” and 14”x17”) | The conventional DR systems are not very flexible for taking difficult views. However, newer systems are being designed to offer greater positioning flexibility. |
| 2 | Compatibility with X-Ray systems | CR systems have been in use for the last few decades and by now all systems are compatible with most existing conventional X-Ray systems in the market. As the CR Scanner and Printer are separate from the X-Ray system, the same can be used to digitise images from multiple systems. | All DR systems come in an expensive package, and may not be currently compatible with all existing X-ray devices. Each X-Ray based machine needs to have its own detector, although the Printer if used can be common. Many models of retrofit DR Systems are available today such from Fujifilm and Carestream that can be used with existing X-Ray machine. |
| 3 | Image Quality & Diagnostic Accuracy | CR images generally have a lower resolution than DR and in some cases even somewhat inferior to film X-ray systems. This may impact diagnostic accuracy. Although diagnostic accuracy is comparable between CR and film-based systems, it is significantly better in DR systems. When single-plate readers are used, old signals need to be erased completely using an erasure lamp. Often if this is not done properly, residual images may overlap with the new image impacting diagnostic accuracy. PSP detectors are in detection position all the time. If the scanners are kept near an X-Ray room, they may sometimes pick stray radiation and result in image noise. | Image quality is much superior with Digital Radiography systems. Detective quantum efficiency (DQE) refers to the efficiency of a detector in converting incident x-ray energy into an image signal. DQE is about 60%–65% with DR but only 30% with CR. Thus, with the use of DR means that patient exposure to radiation is much lower not only because of better DQE, but also due to very low imaging failure rates or lower retakes. DR systems produce higher-resolution images, enhancing diagnostic capabilities. |
| 4 | Image acquisition process, Workflow Efficiency and Integration | Image acquisition process in a CR is labor intensive due to the need for cassette transfer to the plate reader. CR requires the cassette to be removed from the X-ray machine and then placed into a reader to be scanned. This requires the technician to leave the patient and work station with each imaging procedure and wait till the image is scanned to ascertain if it is ok. The PSPs used in CR also requires longer readout and processing time. Since the image acquisition requires the phosphor plate / CR cassette to be scanned in a CR Reader, before the image is displayed on the computer screen, this adds additional step in the process and processing time. On the flip side, as the CR Scanner and Printer are separate from the X-Ray system, the same can be used to digitise images from multiple systems. | Image capture in case of DR system is direct from the detectors to the monitor and is accomplished within 10 seconds as compared to 5-7 minutes in a CR System. Integration of digital images with an Electronic Medical Record (EMR) is simple in DR but not so much in CR. |
| 5 | Throughput | Lower patient throughput due to the longer processing time taken. | High patient throughput due to very short processing time. Even though the upfront cost in DR is higher than in CR, in high patient volume scenario, there is significant cost advantage due to high through put with each machine. |
| 6 | Size | More bulky | Compact profile |
| 7 | Portability | CR system plates are easily portable. Along with mobile X-Ray units the system can be used flexibly in almost all clinical settings. Portable X-ray systems can have imaging plate readers incorporated into them to provide rapid bedside radiographic examinations as well as image presentation, for immediate diagnosis. CR systems currently offer more flexible positioning and varied sizes too. | Currently DR systems are less portable as compared to CR Systems. However newer wireless detectors are available that can be used with any fixed or mobile X-Ray making it highly portable. These wireless detectors simply slide into the bucky table or wall stand just like a plate and wirelessly transmit the image to a viewing console instantaneously. |
| 8 | Radiation dosage | Higher risk of overexposure PSP plates used in CR have a lower efficiency of detection compared to DR detectors. Thus, a higher radiation dose is needed to obtain adequate image resolution. | DR Systems produce much better quality images with half the radiation dosage as compared to CR Systems. |
| 9 | Maintenance | CR systems require regular phosphor plates and CR reader maintenance, adding to ongoing operational costs. They are easy to damage. Erasure lamp replacement is the most common operating cost. | No significant operational cost such as cost of plates and erasure lamps. Online or remote servicing possible to cut down cost of ownership. |
| 10 | Cost of Ownership | CR systems typically have a lower initial investment than DR systems, making them an attractive option for practices with budget constraints. | Higher initial investment – Today many DR systems are available in the market that can be integrated with stand-alone X-Ray machines. On a single system basis, the cost of a DR system may be only just about 20-25% higher. However, if there are multiple systems detectors cannot be shared like a common CR Reader. This makes the DR systems useful only for high throughput facilities. |
Almost all leading manufacturers have DR Systems on offer such as Fujifilm, Agfa, Carestream, Adonis, Allengers, Epsilon etc.
Medical equipment manufacturers are taking several steps towards sustainability, such as improved energy efficiency and use of recyclable material. Decades old technology may be cheaper in terms of upfront costs, however consume far more electricity, use higher radiation dosages and end-up being costlier in the long run to both the owner and the planet.
It is time to move on to completely digital, more efficient processes, high quality images and most importantly lower radiation dosage in our radiology systems.
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