Digital radiography

The digital revolution has been going on for some time now.

Positioning is still as crucial to digital/computed radiography as it is in conventional X-ray production. Digital radiography can use computer programs to improve film quality and to enhance exposures but positioning technique must still be correct.

Many veterinary schools and larger private practices have made the jump to digital and computed radiology (CR) systems.

Marketers and manufacturers have shown us all the beautiful images that can be achieved with these devices and veterinarians are being told that they cannot live without this technology.

Many more equine practitioners, however, are still on the fence regarding these new systems and, though interested, are not sure if they are right for their individual practices. There is no debate concerning the technology or the image quality. But, as Dr. Matthew Wright, a consulting veterinary radiologist says, "Digital radiology has nothing (well, very little) to do with the image."

Mitigating factors

Digital radiology or CR is a system and its use or non-use and the ultimate decision to incorporate it into your practice depend on a list of factors.

Computed radiology is a digital imaging technology incorporating phosphor plates that capture an image made from conventional exposure to X-rays. The latent image from the phosphor plate is then read by scanning the plate with laser light. This process releases a visible light image that is detected and converted to a digital image that is then transferred to a computer screen. This technology was introduced in human medicine by Fujifilms Medical Systems in the 1980s. It should be remembered that CR is a process or system and not a single product. Since these early beginnings there have been many other systems introduced by many other companies and now both human and veterinary products are available.

Comparing conventional radiology to computed radiology is fairly easy on a technology level. Silver halide film (the standard for traditional radiographs) has a limited response to radiation, which means that it cannot tolerate much variation in latitude. Relatively small degrees of under or overexposure will result in an unacceptable image.

Phosphor plates and the resultant computed radiology image, however, have more exposure latitude and are thus able to produce more shades of gray. These images produce higher contrast and, coupled with the computer's ability to enhance or manage this digital information, computed radiography can be adjusted for exposure variation. This factor is one of the strongest points in favor of CR because it means that even inaccurately exposed films can be salvaged and that computer enhancement may optimize the diagnostic value of images.

Spatial resolution

Conventional radiographs have a higher spatial resolution than CR images. Spatial resolution is the number of pixels per unit area. This positive for conventional images does not factor into the discussion however, because much of the increase in standard film resolution is beyond the range of human vision. As technology advances, this resolution difference will prove to be even less of a factor as well. CR, therefore, produces image quality that is as good as traditional films and has the advantage of allowing better contrast in differing areas of the same image through computer manipulation. This explains Wright's comment about CR not being about the image. A well-taken traditional radiograph contains the same information as one taken with CR. The rest of the debate between these two methods of radiology concerns how the images are taken and what can be done with them.

Reduced cost

One of the main advantages cited for CR, outside of the technical issue, is reduced cost for radiology. There are no film costs, no processor maintenance including chemical developers to purchase and chemicals to dispose of. There are no film jackets to buy and no need for the space to store films.

These savings are very real but are dependent on going totally filmless and that transition will cost money to achieve. Remember that the image produced by a CR system that you can view will be influenced by the monitor you view it on and any printed image will be dependent on the printer and paper quality. Printers, ink and paper soon replace processors, chemicals and film and the cost/benefits are not as clearly defined.

Storing

Digital images must also be stored and this part of the patient's medical record must be protected.

Mary E. Andrews, a licensed human radiology technician and event rider, points out that, "There is a need to input information into the computer prior to taking films so there is a delay in the initial film-taking process." This delay is rarely of concern except in emergency situations but because this initial information is the only means of identifying images it is crucial that it be done consistently and correctly.

There is concern that digital images may be "corrected" or manipulated to eliminate defects or alter images. A specific type of image is produced (DiCom) that does not allow any altering of the image once taken. These images are legally acceptable and add another level of integrity to the CR system. Practitioners must still store these images and that takes dedicated computer space.

Attention must also be paid to information storage security, which includes procedures to protect against computer crashes and viruses.

Craig T. Roberts, DVM, operates an equine practice in Ocala, Florida, where he does primarily lameness evaluation and prepurchase examinations. He uses a computed radiology system and protects his images with weekly back-up to an independent hard drive. He maintains fireproof storage of these backed up image files and feels that this system provides him access to radiology images and protection of those same images.

"There is also," he adds, "virtually no problem with lost or misplaced images if the initial data entry is done routinely."

Digital/computed radiography promises to reduce the need for many of the products needed to produce traditional films. Developer chemicals, radiographic film, labels and other items will no longer be necessary with the jump to "filmless" systems. Many clinicians caution that high-speed printers, high-quality paper and toner will simply replace conventional radiology supplies.

Increased efficiency

The next positive point for CR is the idea of increased efficiency because of decreased retakes.

This point resonates with just about every equine practitioner and especially with those in mobile practices. It never seems to fail that when X-rays are taken at a farm in the most distant reaches of your practice territory, the most important view will be poorly exposed or out of position or have patient motion.

When you have to send films off to another veterinarian as part of a pre-purchase examination or for a consultation, those films will come out of the processor too light or too dark even though a set you took on another horse yesterday were of textbook quality.

The belief that CR will eliminate these retakes and save you time, mileage expenses and will improve overall efficiency is one of the biggest factors that is making veterinarians consider this technology.

Many clinicians agree.

Roberts feels that, "Digital radiology produces better films every time, which generates clearer answers for my clients and eliminates the guesswork."

He also feels that the majority of image problems are processing errors and problems with film handling.

Others, however, disagree.

Most equine patients vary widely in size, so a good technique chart should be used. Many radiologists feel that accurate measurements and attention to a detailed technique chart would greatly reduce exposure errors that are currently happening in field X-rays. Patient motion and positioning problems are felt, by some, to be the more likely source of poor equine radiographs, and digital technology will not improve either of those problems.

Speed

Digital images can be easily sent to any location, and this rapid transmission of information is another tremendous advantage of these systems.

Consultation can be quickly done once the images are produced. There is some start-up time involved in the post-processing of images, and this part of using the CR system can be time consuming. Veterinarians with computer expertise and interest will likely find manipulation of images to be easily learned while others may find this aspect of CR to be slightly difficult and an impediment to efficiency. In time, however, this necessary part of the process should be relatively routine.

Color consistency

Even the most correctly processed conventional radiographs will age. They become lighter and more brittle with time and some, depending on developing technique, develop a greenish tint. These problems do not exist with CR images.

If the computer hard drive is properly stored and protected, then those images will exist with perfect clarity indefinitely. Roberts also points out that the CR system itself can remain functional for the life of a practice.

"The Cannon DL plate (used with his particular system and very similar to other comparable systems) begins to lose image quality after two million images," says Roberts, " but even at 5,000 images a year (which would constitute a large number for just about any equine practice), the system would last 400 years making replacement worries unnecessary."

The plate itself must be protected from damage, and there can be concerns about the computer and software needed to process images. These concerns are generally applicable to all computer-based technology and not specific to digital radiology.

There is a very real concern that current technology becomes obsolete very quickly. Remember that digital camera that you paid nearly $900 for two years ago? A newer version with more memory, better picture quality and more bells and whistles is now selling for under $200.

Continued support and repair may also be future concerns with any computed radiology system that is currently in use. Trust in the company and the support representatives for CR is crucial, and there is no easy way to ensure that your system will have adequate backing in the future.

Cost

The last issue to address is that of cost. CR systems are expensive with most units in the $150,000 to $200,000 range.

The average cost per film with these systems is $40 per view. "It's pretty easy to do the math," says Roberts, adding, "if you have a practice that produces enough images per year to justify a $200,000 loan over a five-year period, then it might make sense for you."

Most clients are reported to see the benefit of quality films, more rapid information production and image manipulation for consult as being worth the additional charges.

Wright cautions that many of the veterinarians reporting the benefits and client acceptance of these systems are practitioners who have purchased and are using these systems.

"There is a disconnect," according to Wright, "between reality and perception regarding this issue."

For other practices, there may be no clear-cut advantages to switching to a CR system at this time, especially if the amount of images that you generate would not justify the expense.

For these practices, the answer might be a better quality processor or a more detailed technique chart and better attention to patient positioning.

It's the future

Digital radiology is certainly very exciting and is the future of veterinary radiology.

For some practices that future may be now, and the switch to this new system will allow you to take better images, provide a better service to your clients and make a profit. For other practices, maybe all we need to know we really did learn in vet school. Rededication to taking quality conventional radiographs can allow you to deliver quality medical care and produce a profit while keeping costs in line with your practice and clientele.