What is a “digital” radiograph?
Quite simply, it is a radiographic image that is made without the use of a conventional film-screen (CFS) system. These images are then store on a hard drive (or comparable digital storage media) and view on a monitor. Digital radiography embodies all system types including computed radiography (CR), digital radiography (direct radiography, DR) and hybrids.

Is DR imaging better than CFS?
No. The images produced by CFS are of equal or higher quality than those produced by any digital system. In fact, CFS is considered the gold standard by which all digital systems are measured.

Then why go with digital?
DR offers many advantages over CFS. However, not all of these advantages apply to the veterinary field. Remember, an advantage is only truly advantageous or “real” if manifests in your particular practice. To better understand this, we will compare the top 10 advertised benefits of DR in human medicine and compare those to an average general veterinary practice:

• DR produces a ready to read image very quickly (3-8 seconds), which increases productivity in busy radiology departments (>20 cases per day).
  No Advantage. This would only be advantageous in large private practices, referral clinics and university settings.
• DR allows for fewer repeat radiograph do to technique error (not positioning error).
  Advantage. A recent study found that 34% of repeat films were made because of technique error. This study is from the human field where extensive radiology technician training is commonplace. The percentage of repeat films due to technique error is undoubtfully higher in the veterinary field.
• DR allows images to be sent through networked computers in hospital (intranet) as well as to other doctors/specialists in remote locations (internet) for consultation.
  Advantage.
• DR offers increased dynamic range. This allows visualization of both soft tissue and bone details in the same exposure with post-processing manipulation of the image.
  Advantage.
• With DR there are no films to lose. Images are preserved on a digital storage media (i.e. hard drive) forever.
  Advantage.
• Stored DR images never change hence no information is lost. Unlike processed films which have the potential to degrade over time (i.e. brown films).
  Advantage.
• DR does not require chemical processing, alleviating OSHA concerns.
  Advantage.
• DR does not require film processing, eliminating the cost of film, chemicals, processor and processor maintenance, and time required to perform the maintenance.
  Advantage.
• DR’s digital format allows for easy duplication for the client’s use and can be store on most mobile storage medias (i.e. floppy disk).
  Advantage.
• DR eliminates the costs associated with film storage.
  Advantage. Hard drive space is cheap compared to physical storage space.

9 out of 10 advertised advantages of DR are directly applicable to the veterinary field.

How does DR work?
CR has many similarities to CFS radiography and is essentially used in the same manner. Both use cassette based phosphor screens, which absorb x-rays and promptly emit light. In CFS, the emitted light is use to create a latent image that is later chemically developed into a viewable image or radiograph. With CR, this light is useless. So, how does it work? The CR phosphor retains about 50% of the x-ray energy via electron trapping. This stored energy is in image form and is emitted or released when scanned by a laser. The intensity of the energy is proportional to the amount of attenuation. The released energy is recorded and displayed as a digital image. The CR image is available for interpretation in about the same time as CFS (approximately 90 seconds). The CR cassettes have the potential for thousands of exposures allowing for years of service.
DR’s technology differs greatly from CR and CFS applications. Essentially, the only similarity is the x-ray tube. There are two types of DR, direct and indirect. Direct DR is a seamless process, using semiconductor material, which converts x-ray energy directly into electrical energy. The electrical energy is used to create a digital image. No light is emitted which is a major advantage of direct DR. Direct DR is the most expensive technology. Indirect DR has an added internal step and light emission, potentially leading to minute image degradation. Indirect DR is slightly less expensive than direct DR. Currently, most systems offered to the veterinary field are indirect DR. These systems or plates are retrofitted to work with your existing x-ray table. The DR plates are electronically erased and synchronized with the x-ray machine prior to each exposure. DR images are displayed within 3 to 8 seconds.

What is the difference between CR and DR?
One of the major advantages of both DR and CR is the inherently expanded latitude. So, what does this mean? In radiography, broader latitude means broader exposure flexibility. No more cumbersome CFS technique charts. All exposures are made using a select number of settings. Under and overexposed films are digital corrected, hence, as long as the animal is properly positioned, a repeat exposure is not needed. Increased latitude allows for high detail visualization of soft tissue structures and high contrast structures such as bone on the same image. The result is a decrease in personal exposure and an increased in profitability.
The advantages to CR are the reusable detector plate, which can be used with any and multiple x-ray machines. With proper handling and care, the phosphor plates will last for years. There are no required x-ray table modifications. The cassettes can be used from tabletop, buck tray and positional radiography. The disadvantages are the increased time needed to produce an image (similar to film-screen systems) and the potential for cassette damage and cost of replacement.
DR’s main advantage is time. Images are displayed rapidly allowing for essentially instantaneous assessment and positional correcting, if needed. DR’s biggest disadvantage is cost with the average system selling for approximately 2.5 to 3 times the price of CR. Another major disadvantage is the mounted or fixed detection plate, eliminating the ability to perform positional radiography and multiple machines.

So, is DR for me? If so, which system best suits my practice?
As always, cost is a major contributing factor when considering a technological investment such as DR. However, it is not considered paramount. The most important factor to look at is production or expected production. If the limiting step in your radiology department is time, then direct or indirect DR should be considered. If not, CR is a reliable, quality, alternative. Both CR and DR produce high quality images with only a negligible difference. If your practice is radiographing less than ten cases per day, CR is a smart choice.
There are several aspects to keep in mind when choosing a system. The company’s history, are they an established company that will not only supply a quality produce, but also quality service, training and support? Do they offer an in-house service contract with local service representatives or is this work contracted through another company who may or may not have local service? When considering direct or indirect DR, plate size is an issue. Smaller and non-standardized plates mean less information or more exposures. Plate resolution, the plate is only as good as the image it can provide. Remember increased resolution means better quality images, but it also means increased cost. How easy is the system to use? As we all know, if it is not user friendly, your staff will not want to use it. Does the company stand by their product? Do they offer prompt service and repair? Will they offer a loaner system if needed? Are the images universally DICOM compatible? Is system integration possible with multiple or all PACS systems, or is it limited? If choosing CR, as the cost of DR decreases, is there the option to upgrade seamlessly and cost effectively through that company?

As you can see, there are many questions to consider which go beyond the product itself. Do the research and choose wisely. If you need further assistance please feel free to contact us at info@illumipet.com or call 206-755-0704.