The State of the Art
Innovations in CBCT and digital x-ray imaging
Dale A. Miles DDS, MS, FRCD(C), Dip. ABOMR, Dip. ABOM
Of the x-ray imaging modalities available to dentists, cone-beam computed tomography (CBCT) is rapidly becoming the most useful in the dental office. While the most widely-used modalities are still bite-wing and panoramic imaging, these popular 2-D imaging methods are very limited in the information that they can offer the dentist to help with daily clinical decision-making. An increasing number of US dentists are finally adopting digital x-ray imaging, either direct (solid-state detectors) or indirect (phosphor plates), to replace conventional x-ray film in their practices. Image acquisition is quicker, the capability of performing image processing creates more diagnostic images, and the dose of radiation delivered to the patient is substantially lower. In addition, the ability to display more understandable information to the patient to help in their own treatment decisions provides a major advantage. The author has developed a preference for solid-state wired detectors over reusable phosphor plates; however, there is an advantage to using phosphor plates for pediatric and for some endodontic patients because the “wire” of the solid-state sensor may become problematic when used in children or when the receptor is placed behind a rubber dam. With increasing adoption of panoramic machines that are capable of opening the inner proximal contacts and displaying small carious lesions in high detail without putting something in a patient’s mouth, phosphor plate technology will probably be relegated for use among these specific patient groups. In addition, because many manufacturers are producing CBCT machines that include the capability to produce a high resolution, low dose 2-D panoramic image, the office of the future will probably only have one or two, possibly handheld, intraoral x-ray devices and this “multifunctional panoramic on steroids,” which allows 2-D grayscale panoramic imaging as well as 3-D CBCT. Consequently, film-based imaging is likely to slowly fade away, with phosphor plate technology continuing to have a limited role as dentists increasingly embrace digital panoramic and CBCT solutions.
A Decade of Innovation
During the past 10 years, all manufacturers have improved their machines, and most now feature a selectable, variable field of view, improved scatter rejection software, and optimized image processing algorithms to display the best image possible on the clinician’s monitor. In an effort to minimize motion artifact, manufacturers have also made improvements to their positioning platforms. Motion artifact will always degrade the CBCT image. Dentists evaluating CBCT machines for purchase should focus critically on each manufacturer’s solutions for stabilizing the patient in the machine. They need to seriously consider, at the top of their list, those CBCT machines that have been engineered to eliminate as much patient movement as possible.
Need for Education
Many of the problems and issues experienced by CBCT users could be eliminated if manufacturers offered robust, multi-day programs to educate their clients as part of the purchase price. Two of the most commonly reported impediments for dentists considering purchase are the fear of missing something in the scan and the fear of being sued because of it. Much of this fear could be mitigated through targeted education, including:
• in-office training of the dentists and their staff immediately following purchase so that all operators know how to properly position the patient and export the volume in a format that is compatible with third-party software (not just burn a CD-ROM with the company’s proprietary software).
• more detailed training for the dentists and their staff in the use of often overlooked image processing tools, such as those that create a maximum intensity profile and 3-D surface rendering of the image data, as well as their other more common tools to optimize images prior to diagnosis.
• improved after purchase follow-up support, especially with regard to response times.
• additional training for dentists in multi-planar anatomy, the use of implant planning tools, risk and liability issues, and documentation of findings using standardized reports.
On the Horizon
Many possible hardware innovations for CBCT are on the horizon, including faster computer processing solutions for accelerated image reconstruction. Currently, positioning and capturing a cone beam image takes less than 20 seconds. It is the image reconstruction phase that slows down the overall procedure. Just as Apple introduced parallel processing to increase computer speed, hardware is being developed to greatly reduce the image reconstruction time. To reduce the size of the focal spot and further improve the image resolution, some manufacturers are migrating to rotating anodes In machines that use the typical stationary anodes present in intraoral x-ray tubes, the target anode has a 1.0 mm focal spot size and can only withstand the associated heat for a brief period of time before being destroyed. If the anode rotates, the actual focal spot size can be reduced to as small as 0.1 to 0.2 mm. And the smaller the focal spot, the greater the eventual image resolution. To further the miniaturization of CBCT and make the machines even lighter and more ergonomic, carbon nanotube technology may be harnessed for x-ray production. Carbon nanotubes are capable of delivering very stable high currents; they are currently being investigated for use in intraoral x-ray machines. Other possible innovations include improved head stabilization to further reduce motion artifact and the development of a CBCT machine specifically designed to capture images of soft tissue, such as the temporomandibular joint disk. Finally, it is very likely that most of the improvements impacting CBCT imaging will come in the “software arena.” Software engineers are already working on (and, in some cases have developed) solutions to:
• improve programs for airway analysis;
• improve programs for elimination of soft tissue artifact;
• produce faster, more intuitive programs for implant site assessment;
• provide 3D cephalometric analysis of the data volumes;
• provide 4D imaging for jaw motions; and
• produce software for image-guided surgery.
Cloud-Based Image Management
Cloud computing/cloud storage is just a metaphor for moving all of your data from your local hard drive to the Internet. Just as you currently move your pictures, videos, and other data to off-site Internet storage, data produced by CBCT devices can also be moved, stored, and accessed on the Internet from a “dashboard” interface. Cloud-based image management solutions are being developed by companies and entrepreneurs to offer services to clinicians who want to store their cone beam data, access it whenever possible, request radiographic interpretive reports, order surgical guides, and conduct online consultation by logging onto any computer or mobile device (Figure 1). Some stakeholders view the movement of this kind of data to the cloud as inevitable. As more clinicians move to this environment, the associated costs for storage and usage will reduce. Many software applications and programs will operate even more securely in the cloud, allowing use in real time by clinicians. The data uploaded and stored to the cloud can then be accessed by staff, patients, and other clinicians with appropriate user permissions. Other advantages include automatic updates for the software used within this environment and enhanced security for the data stored there. Unfortunately, this does not mean that there are no risks to using the cloud, as these types of services can become prime targets for hackers.
About the Author
Dale A. MILES, DDS, MS, FRCD(C), Dip. ABOMR, Dip. ABOM CEO
Cone Beam Radiographic Services
Fountain Hills, Arizona
