INTRODUCTION

Digital Technology has become more and more integral to all aspects of our lives over the past two decades. In almost all cases digital technology has improved our lives by making things we need less expensive, better, more reliable and easier to use.

Dentistry has been steadily incorporating digital technology into the way we manage our practices. First we put personal computers in the front office to manage the business side of our offices, then came chair-side computers to help us increase the efficiency of our clinical record keeping. Some of us in Orthodontics also started using computerized treatment planning tools and digital imaging technology to help us better care for and inform our patients. The only missing piece has been radiography where most of us are still doing things the old fashioned way.

The primary reason that Dentists have not been quick to adopt digital radiography is because, until now, there has been no technology that provided a total replacement for film in dental radiography. There have been some intra-oral devices available for digital radiography but they were only offered in some of the sizes of film Dentists use. So, even those Dentists who bought into these digital radiography tools still had to keep a film processor in the office.

This article will describe a new digital radiography technology, the DenOptix system by Gendex, that has the capability of completely eliminating all silver-halide based film from dental offices and, in doing so, completely remove the last impediment to a paperless dental office.

DIGITAL RADIOGRAPHY

The history of digital radiography in dentistry is fairly short. The first intra-oral CCD (charge coupled device) sensors were introduced in the mid-eighties by Trophy. Many competitors (most notably Schick in the United States) soon followed but the fundamental limitations of this technology remain unchanged. The primary advantage of this competition was a lowering of prices.

The direct wired systems utilize Charge Coupled Device (CCD) technology. (A CCD is the device inside your video camera that changes light into electronic images). CCD sensors, when coated with the appropriate phosphors, can be used to record X-ray images, too. Since CCD sensors cannot store information, a wire connecting the sensor to the computer is required. Most Dentists see the wire as a major impediment to the convenient use of this technology.

CCD based dental systems are, for the most part, limited to intra-oral radiography because of the size limitations of these extremely expensive sensors. Several manufacturers have recently introduced CCD based sensors for their pan/ceph X-ray machines. Unfortunately, due to the cost of the large sensors required for this application, the prices of these digital panorex machines are prohibitively high. Retrofitting existing panorex machines with CCD sensors is usually not an option. The Orthodontist is required to purchase a new pan/ceph machine and still needs his film processor for the ceph films. There is also a slit-scanner ceph unit on the market that uses a CCD sensor to generate ceph images. In addition to the disadvantages listed above for the panoramic units, the ceph machine requires several seconds to complete a scan. During the scan the patient must remain perfectly still.

In orthodontics, which relies heavily on panorex and cephalometric radiographs, the only viable option has been to scan radiographs with either a flat bed scanner or direct video recording onto the hard drive. Even with this extra step, the advantages to the Orthodontist are substantial. On screen cephalometric landmark identification and the application of cephalometric analysis software, as well as case presentation and marketing have driven the need to digitize large films in the orthodontic office. Evidence for this can be seen at every major orthodontic convention over the past several years where large crowds can be found at the high tech vendor's displays.

THE DENOPTIX SYSTEM

The DenOptix System The photograph at the left shows the combo version of the DenOptix scanner, two carousels and a variety of storage phosphor Imaging Plates. The DenOptix scanner is the approximate size and shape of a large home breadmaker and is connected to a computer in the dental office. This model has been on the market for several months in Europe and was introduced to the US market at the mid-winter meetings in Chicago. It does all IO and Pan formats. A new version of this scanner with cephalometric capability will be introduced at the American Association of Orthodontists meetings in May. The combo DenOptix Digital Imaging system includes accessories needed to generate digital images in all common size formats from #0 intra-oral through panoramic. The new ceph version will also be able to work with ceph sizes (8x10 inch or 18x24 cm).

The DenOptix digital radiographic system, unlike CCD based systems, uses a Film-like sensor to capture and store the radiographic image. Instead of film, this system uses storage phosphor Imaging Plates, which are thin and flexible like film and can be produced in the same sizes as film. For this reason, the DenOptix system enables both intraoral digital radiography, and digital panoramic and cephalometric imaging, too.

Storage phosphor based imaging technology has been used in medicine for many years but the high cost of the scanning devices has prevented the use of this technology in dentistry. These medical systems, which cost several hundred thousand dollars, are typically hospital based and used for chest x-rays and other large-format studies. The key to the DenOptix system has been the development of an affordable scanner that produces extremely high quality images captured on Imaging Plates.

The intra-oral Imaging Plates, which are housed in disposable sanitary barriers, are exposed just like traditional film with one important exception: with storage phosphor technology the exposure settings on the X-ray machine can be reduced.

Storage phosphor Imaging Plates are thin and flexible and do not have wires attached. The Imaging Plates can be bent to fit the palate and are indistinguishable to the patient from film. For each patient, all necessary images can be taken in sequence (just like film) and the Imaging Plates set aside until the session is complete.

The Imaging Plates are then taken to the DenOptix scanner and loaded on a carousel (about the size of a coffee can) which is then placed in the machine and the scan is initiated from the computer. The carousel can accommodate as many as 29 Imaging Plates at one time. Intra-oral Imaging Plates are available in all of the same sizes as film (#0, #1, #2, #3 and #4). They are the exact same size as film and their full surface is available for capturing the image.

The process of loading the scanner does not require a dark room since storage phosphor Imaging Plates are only slightly sensitive to visible light. A subdued light environment is fine. Scan times vary depending on the surface area being scanned. One to eight bite wings take about one and a half minutes. A panoramic scan takes just under 3 minutes. As soon as the scan is completed the DenOptix software will automatically send the images to the computer in the correct operatory.

Loading the Carousel The simple process of loading a #2 intra-oral Imaging Plate is illustrated on the left. This process does not need to be done in a dark room. Subdued lighting (such as the old dark room with the door left open) is acceptable. Note: The plastic IO holder is removable to allow sanitizing if contaminated.

After the scan is completed the Imaging Plates are placed face down on a bright viewbox for a few minutes in order to erase the residual stored image. The Imaging Plates are then slipped into fresh sanitary barriers and are ready for the next patient. Unless physically damaged, Imaging Plates are good for thousands of uses.

One of the major problems that has kept digital dental radiography from being more widely accepted is the inability of most systems to generate both panoramic and cephalometric images. Any office taking these types of extra-oral images must still rely on chemical film processing and all of its incumbent costs and drawbacks. Those previously excluded from being able to realize the full advantages of digital dental radiography include the orthodontist, oral surgeon and large percentage of general practitioners who own panoramic machines. The development of an imaging system that can also be used for the large extra-oral formats will eliminate this problem.

For panoramic and cephalometric imaging, the process is similar to that described for intra-oral imaging except that there is no need for a sanitary barrier. The Imaging Plates are the same size as the lanex screens that are installed in pan and ceph exposure cassettes. Before using the cassette for storage phosphor, the user must simply remove the lanex screens from the cassette and replace them with a single panoramic or cephalometric Imaging Plate. The exposure techniques are identical to the procedures used for film. Since Panoramic and Cephalometric X-ray exams are already a low dose technique, the X-ray machine settings are not changed. Once again, a darkroom is not required and the screens can be reused for thousands of cycles. The DenOptix scanner has the ability to scan intraoral and extraoral Imaging plates at the same time.

Another hurdle faced when installing a CCD based system in large multi-operatory offices is the cost of the CCD sensors and the requirement for the sensor and computer to be in close proximity to the patient. Large offices must either purchase a system for each operatory, take radiographs in a dedicated operatory, or move a single system around the clinic on a cart. With storage phosphor Imaging Plates costing a tiny fraction of what CCD sensors cost, a large clinic can use dozens of phosphor storage screens, and a single DenOptix scanner at a central location. The images can then be viewed at any station via network.

The images produced by the DenOptix system are extremely high quality and have distinct advantages over film in terms of the amount of information they contain. From a diagnostic standpoint, the biggest advantage of storage phosphor technology is the inherently long linear dynamic range of data captured in each image . The dynamic range is the relationship between the radiation dose and the optical density, or range of light to dark. Silver based film has a dynamic range that is linear only over a small range of about 1000:1. This characteristic of film requires exposure and development techniques to be very accurate in order to produce a useful radiograph. There is little tolerance for error when using film.

A long linear dynamic range (such as exhibited by storage phosphor technology) allows the viewer to adjust the display of the image through the portion of the dynamic range that has the most useful diagnostic information, and virtually eliminates the possibility of over or under exposing an image.

An example of how this feature can be useful can be found in the viewing of a cephalometric image captured with a storage phosphor Imaging Plate. The soft tissue profile can be seen in extraordinary detail and contrast as the viewer adjusts the display through the linear dynamic range of the captured image. This eliminates the need for a soft tissue filter.

Conversely, images of structures in areas of high bone density, such as the condyle, can be enhanced by moving the opposite direction along the dynamic range. Since there is so much potentially useful information available in the long linear dynamic range of an image captured with the DenOptix system, only a portion of this data is actually viewed on the monitor at one time.

Two Versions of DenOptix carousels are shown here. The one on the left is the version used in the currently available combo unit. The carousel on the right fits the new "ceph" version of the DenOptix system.

The DenOptix software is very well thought out and provides a number of tools to view and manage images. Images that have just been scanned are assigned on screen to a patient's file and laid out in any one of a number of thumbnail displays. Within the patient’s file, images can be organized by date, tooth # or image type. The monitor screen is arranged like a viewbox with a tool bar to the right and the patient's file of thumbnail images below. Once an image, or images, is placed on the viewbox portion of the screen, they can be manipulated using one or more of the tools.

The image manipulation tools include a magnifying glass feature, Inversion (changing from negative to positive) and a number of filters to help the dentist look for detail in the image. The software allows linear and angle measurements and contrast adjustment. In addition, drawings and text can be added to the image for patient education or documentation. The optimal portion of the dynamic range of the image being viewed can be automatically adjusted or can be controlled by the viewer. For the orthodontist and oral surgeon, DenOptix image files can be exported to most popular file formats for use with treatment planning software packages.

IMPLICATIONS

This technological breakthrough promises to benefit orthodontics more than any of the other specialties. While the orthodontic community has been the quickest to accept on screen diagnosis, treatment planning and case presentation, their reliance on extraoral films has until now precluded orthodontists from enjoying the full benefits of digital radiography. The obvious benefits begin with the elimination of the darkroom, processor and flatbed scanner, all capital expenses. With no need for chemical processing, the monthly costs of chemicals, upkeep of the processor, film mounts and film are eliminated. In a large office, the costs of these consumables can be substantial. There is also a significant environmental benefit to this technology since the heavy metal waste stream that results from chemical film processing is eliminated.

One of the most exciting aspects of digital radiography in the orthodontic office is the potential to transmit images to another dental office via modem. Since most orthodontic offices routinely send copies of films to other specialists, as well as to the referring general dentist, this feature can provide substantial benefits. Sending digital images directly over the phone lines virtually eliminates the chances of losing films or having them delayed by the post office. The images received are at full quality rather than a frequently inferior copy of a film, and can be sent to an indefinite number of locations. The ability to electronically send images to another office allows for consultation between professionals in an almost instantaneous fashion. DenOptix images can be printed for those dentists who do not yet have the ability to electronically receive images. Copies can also be printed for patients. Because of the ability to optimize the display of an image, a dentist may chose to enlarge the third molar regions of a panorex and print only these areas of greatest diagnostic value before sending. Annotations can also be printed on the image.

Dental radiology recently celebrated its one-hundredth birthday, and has for the most part, remained relatively unchanged for its first century. The DenOptix system, based on phosphor storage screen technology, finally enables digital radiography to replace silver based film in the dental office, and will lead dentistry into the next century.

Panoramic Images are available in less than three minutes. Both 5 X 12 inch and 15 X 30 cm formats are available.

USING DIGITAL IMAGES WITH TREATMENT PLANNING SOFTWARE

First - Export the DenOptix image file into a format compatible with your treatment planning software. In this example, we exported to a jpeg format.

Next - Import the jpeg file into your treatment planning software and proceed as usual. The screen shot above is courtesy of OrthoVision.

Last - Print the treatment plan. In this example, the radiograph was eliminated and only the results of the orthometric measurements printed for the record.

SUMMARY OF BENEFITS OF STORAGE PHOSPHOR TECHNOLOGY IN DENTISTRY

The technology reviewed in this paper offers a number of significant to Dentists. The value of specific benefits of this technology vary from specialty to specialty. The major benefits of this technology include:

 ABOUT THE AUTHOR

Jon M. Menig, DDS, is a practicing orthodontist in the Sierra foothill's town of Nevada City. Dr. Menig received his DDS from UCSF in 1984 and did his orthodontic residency under the leadership of Harry Dougherty at USC. Serving as a consultant "wet fingered" orthodontist for Alara Inc., the developer of the DenOptix system, Dr. Menig served as a bridge between this Silicon Valley start up company and the orthodontic field.