INTRODUCTION

The inevitable shift towards digital x-ray imaging continues. In the June 2002 issue of Dental Products Report (DPR), Gail Weisman reports that digital radiography "is being used by 14% of current respondents". What does that mean? DPR has conducted surveys of dentists in the US by sending 2000 questionnaires randomly to dental offices. In 1999, only 8% of those responding said they'd adopted digital x-ray systems. The same survey sent recently yielded the 14% figure. The response rate for these questionnaires, however, was about 12.2%. While this number is small, there seems to be a trend. More of us are adopting digital technology, even digital x-ray systems.

"Change is Good!" Adopt and Adapt

As a dentist you must adopt new technology all the time. Then you have to adapt the technology to your office and practice philosophy, and you have to adapt to the technology yourself. You cannot learn new techniques vicariously. Ours is a "hands-on" profession. Digital radiology or digital imaging is no exception. The good news is that it's not as hard as you think. I've said it before. I'll say it again. The only real change or "paradigm shift" when adopting digital imaging is electronic image processing (EIP).1,2 Dentists can now perform simple image altering tasks to see disease features better. This will help us make better diagnoses and better treatment decisions. Medical radiologists have been doing this for 10-20 years with CT (computed tomography) and MR (magnetic resonance) images. Every image captured digitally in these imaging modalities is altered form the original. Chest images, breast images, neurologic images --they're all subjected to EIP on the working monitor so that the clinician can detect lung nodules, breast calcifications and small density differences between similar gray matter and lesions in the brain. This is the rule, NOT the exception. We want to process the image electronically to detect disease better (figure 1). If we want to move forward with our medical colleagues, instead of falling further behind, we have no choice but to adopt the new digital imaging systems. The most frustrating thing for a dentist is to try to practice new dentistry with old tools. Adopt and adapt, you have little choice.

Figure1
Panoramic radiograph taken of a patient with a "mixed" dentition. The radiograph is overexposed.

Figure2
Same radiograph as in 1a but scanned in a desk top scanner and processed with an "equalization" filter in PhotoshopTM 3.0. This simple EIP step has effectively recovered information in an otherwise undiagnostic film.

Why would you want to change?

Besides all of the advantages of digital imaging listed in Table 1 below, there are other reasons to change to digital x-ray imaging systems. If you are considering retiring in the next 5 years, you'd like to make your practice as attractive as possible to the buyer; the more contemporary your office equipment, the more attractive the practice. And, if you're contemplating hiring a new associate, digital imaging systems show that you are practicing "high-tech" dentistry. Similarly, your patient's perception of how "up-to-date" you are as a dentist is enhanced by digital x-ray systems with their instant image display and their reduced x-ray dose. If you are a recent graduate setting up a practice, or a clinician moving to a new office, there are reduced initial and on-going costs associated with digital systems. The annual savings in "tech time" alone can be enough to pay for the system.3 It is true that doctors have experienced problems with solid-state sensors, but in most cases the company has replaced the system according to the users I talk to constantly at dental meetings. But, with sensors there are no chemical costs, film costs or hazardous materials handling costs. Film mounts are gone too. These materials and services are eliminated and thus reduce your supply costs. If you must have a "hard copy", photographic quality paper can be used for your x-ray images. And, this paper can be used to archive your clinical photographic images as well. If you are concerned that the paper image will deteriorate with time, don't be. The archived digital image on your hard drive, CDROM or DVDROM will last longer than your practice! You can always print a new, perfect image.

Table 1 contains a list of the positive attributes* of digital imaging systems.

But, what's wrong with film?

Film as an image receptor for dental imaging/interpretation tasks is excellent. I have never said that it wasn't. But, since it is at once the receptor, the display and the archiving media, it does have some significant drawbacks.
We've all tried to "read" x-ray films that were a little too light or a little too dark in our practices. Even in the best dental practices, quality control of the solutions in our processors "breaks down". This is not the case with digital images. Their density and contrast is much more reproducible. And, if the image is a little light or dark, no re-exposure of the patient is necessary. You simply perform EIP on the image to optimize the image characteristics .
A #2 dental film as a display "mechanism" is also suspect. The image is small. Dentists rarely use darkened environments to view these films. And, in most offices, dentists do not magnify the image to help them view the potential disease changes. By using a computer monitor, dentists automatically use image intensification (II) inherent in the system. This II process optimizes the image for the poor viewing conditions (ambient light from windows, fluorescent light, etc…) in which most practitioners interpret the radiographic findings. In addition, all monitor x-ray images are magnified when viewing. Patients can finally see changes on the image when they're viewing the computer screen. It's like watching television for them, an activity they are all familiar with. You don't have to invite them out of the chair to try to show them the tiniest black "dot" on the distal of that second premolar, only have them to remark "Boy, Doc, you sure got good eyes. I don't know how you can see those things!"
Finally, film as an archival device cannot compare to binary data; that is, a digital image stored on a hard drive or other storage media such as a CDROM. We all have yellow or brown films in our cabinets from poor fixation by chemical image processing. I know I have been embarrassed pulling such images out of a chart I haven't seen in months to show the patient. This does not happen with digital images. The image you "save to disk" will keep its image fidelity forever. You can print a "hard copy" of this data anytime you want and it will look the same as the day you stored it. Digital images have lots of advantages, some of which we don't have to think about.
Eastman Kodak has announced that they will no longer manufacture Ektaspeed PlusTM film after December 2001. They have introduced an even faster film, InsightTM (an F-speed film) to replace Ektaspeed. In fact, because of the rapid acceptance of InsightTM film by dentists using D-speed (UltraspeedTM) film, Kodak will probably abandon D-speed film production in the near future. Furthermore, Eastman Kodak is examining the need to introduce even more "digital" dental products, like their DMI 1200TM inkjet printer and their DC290TM still camera to our profession. They do, after all, make both CCD (charge-coupled device) and CMOS (complementary metal oxide semiconductor) devices for many other camera and video camera manufacturers. If the premiere dental imaging company in North America is "going digital", how long can we survive with our film-based imaging systems?

Who are the current digital x-ray "players"?

Boy, this list changes constantly! But why is that? In large part, it is because of our profession's reticence to move forward in a digital world. According to Arthur C. Clarke, new ideas pass through 3 periods.

These are:
1. "It can't be done.
2. It probably can be done, but it's not worth doing.
3. I knew it was a good idea all along"!

Might the same be said for digital x-ray imaging. I might take a little "poetic license" with this concept with regard to dentists adopting digital sensor systems. I would say it will go something like this:
1. I don't need digital x-rays.
2. I see the advantages, but I'll stick with film.
3. God, I wonder how I ever practiced without it!
4. My staff would mutiny if I ever went back to film!

Table 2 lists the current "solid-state" sensor vendors (direct digital capture systems) and their products.
Table 3 lists the companies offering storage phosphor or reusable storage phosphor (PSP) systems (indirect digital capture systems).

Table2
Direct Digital Sensor Systems
intraoral

*all of these sensor systems have high spatial resolution capability - from 8-22 lp/mm.
** cost is for "basic system", some manufacturers have additional costs for "capture system", software, and/or "upgrades".

Table 3 below lists the manufacturers of photostimulable (reusable) phosphor systems. These should be thought of as indirect digital systems since the receptor is exposed to x rays and then processed, by scanning with a laser beam to release the light energy stored, to create an image from the electronic signal. Unlike CCD or CMOS detectors, the phosphor-based imaging systems are 2-step systems like film, requiring similar infection control steps and handling. They also need to be "discharged" by flooding their surface with high intensity light, like that from a viewbox, for several minutes before reuse. Failure to discharge the previous image completely, may result in a "residual" image on the phosphor plate that can interfere with the next image. These indirect systems are more time consuming, but do result in a "digital" image that can be subjected to EIP. An advantage of PSP systems is a wide dynamic range (like gray scale) which exceeds 10,000:1. This more than compensates for their lower spatial resolution of 6-9 lp/mm.

Indirect Digital Receptor Systems
(intraoral)

Summary
From the preceding discussion, we see that there are many digital x-ray systems to chose from, that the systems have many advantages over conventional film-based radiography, that major companies like Eastman Kodak are continuing to transition to digital products, and that the change to digital in both our consumer and professional worlds is inevitable. The question to ask yourself is not "Should I change?", but rather "When do I change?". My suggestion is to do it sooner than later. If you've adopted computers into your office, it's only a matter of time before you will "go digital".

References
1. Miles DA: Advances in Imaging in Oral Medicine, Alpha Omegan 94(2): 24-28, 2001.
2. Miles DA: Understanding Digital Radiography, 2001 Technology Guide, Dental Practice Report, 8-12, 2000.
3. Miles DA, Langlais RP and Parks ET: Digital X-rays Are Here; Why Aren't You Using Them? CDA Journal 27(2): 926-934, 1999.

Web Addresses (URLs) for the manufacturers in the article:
AirTechniques http://www.airtechniques.com
Cygnus Technologies http://www.cygnus-technologies.com/
Dentrix Dental Systems http://www.dentrix.com
Dentsply Gendex http://www.gendexxray.com/
Dent-X http://www.dent-x.com/
DEXIS http://www.dexisusa.com/
Fimet http://www.fimet.fi/
Eastman Kodak http://www.kodak.com/US/en/health/index.jhtml
Instrumentarium Imaging http://usa.instrumentarium.com/
Orex http://www.orex-cr.com/dental.html
Planmeca, Inc. http://www.planmeca.com/
Schick Technologies http://www.schicktech.com/
Sirona USA http://www.sirona.com/e/index2.html
Soredex http://www.soredex.com/
TREXTrophy http://www.trophy-imaging.com/explorer/index.html