Cone Beam Computed Tomography Trends Toward Hybrid Systems and Third-Party Software Use

Allan G. Farman, BDS, PhD, DSc, MBA; Claudio M. Levato, DDS; William C. Scarfe, BDS, FRACDS, MS; Doug Chenin, DDS

Recently, cone beam computerized tomography (CBCT) has been taking dentistry by storm. This article is the fourth in a series of updates that the authors have written for Inside Dentistry. Previous articles covered basic principles (January 2007), an update following the 2007 Cologne Dental Show (June 2007), and a description of the American Dental Association’s “Education in the Round,” which featured live demonstrations of four CBCT systems (January 2008).^1-3 This new update explores the rapidly changing world of CBCT at the time of the 2008 Chicago Midwinter Meeting. It also provides insights into the expanded role of CBCT planned for the American Dental Association (ADA) Annual Session in San Antonio, Texas, which will be held October 16-19, 2008.

The Move to Smaller FOV and Hybrid Solutions

As recently as this past January, CBCT systems were dominated by large field of view (FOV) systems designed for capturing maxillofacial structures to enable orthodontic and oral surgery planning. Some of these systems could be collimated to affect smaller FOV. As the cost of the CBCT system is greatly influenced by the cost of the sensor, and as sensor costs are largely a factor of sensor size, such large FOV systems were substantially more expensive than machines combining digital panoramic and two-dimensional (2D) cephalometric systems. Planmeca USA (Roselle, IL) was the first to incorporate a small FOV three-dimensional (3D) sensor to their ProMax line, creating the ProMax 3D CBVT (Cone Beam Volumetric Tomography), which also can be retrofitted to any of the previous ProMax digital models. At the 2008 Chicago Midwinter Meeting, the major trend in CBCT was toward smaller, more affordable FOV units, fitting in an office with a footprint similar to a standard panoramic system. Further, several new systems now provide a hybrid solution including digital panoramic, small FOV CBCT, and, sometimes, standard 2D digital cephalograms as well. The sticker price for these all-inclusive units generally ranges from $100,000 to $130,000, not substantially more than high-end digital panoramic/cephalometric units alone. Examples of hybrid units are the Veraviewepocs® 3D (J. Morita USA, Inc, Irvine, CA), the Picasso Trio (E-Woo Technology USA Inc, Houston, TX), the Scanora® 3D (Soredex, Milwaukee, WI), and the Kodak 9000 3D (Carestream Health Inc, Rochester, NY) (Figure 1a and Figure 1b). At time of this writing, the Kodak 9000 3D, Scanora, and Picasso Trio hybrid solutions were US Food and Drug Administration (FDA)-approved and the Veraviewepocs 3D had been submitted to the FDA for evaluation and was awaiting approval. Dedicated CBCT systems with small FOV previously included the Prexion3D (PreXion, Inc, San Mateo, CA) and the 3D Accuitomo (J. Morita USA, Inc). To these, the GX CB-500™ (Gendex Dental Systems, KaVo Dental Corp, Lake Zurich, IL) can now be added, which is essentially a smaller version of the i-CAT® (Imaging Sciences International, Inc, Hatfield, PA), which is suitable for dental implantology, but not for orthodontics or extensive oral surgery (Figure 2).

The rapid growth in CBCT has been driven predominantly by the implant market, and with the increase in the number of vendors bringing CBCT units into the dental market, the landscape of dental imaging is irreversibly changing. This continued growth only can be sustained if the applications were expanded to provide cost-effective solutions for the general dentist. Currently, most general dentists are standing on the sidelines waiting to see what magic these units can deliver in return for their $100,000+ investment. To get them to embrace this technology will require real solutions and easy-to-implement applications. Historically, dentists are conservative in incorporating new applications. For example, digital intraoral radiology has been available for 20 years, and still less than one third of dentists use this technology.

The authors believe that the trend toward hybrid CBCT systems will be comparable with the move toward hybrid automobiles. It is simply a matter of cost. For automobiles, the sharp rise in gasoline prices means that the combination of electric and internal combustion engines makes sense. For the average dental practitioner, while a large FOV might be attractive, the economy of size can reduce costs substantially—and when combined with digital conventional panoramic and 2D cephalograms in a reasonably restricted space—provide for most imaging needs.

There are some definite advantages to a small FOV in addition to outlay on capital costs. First, a small FOV means that high-resolution images with a spatial resolution down to 0.076-mm isotropic voxel size (achieved with the Kodak 9000 3D system) can be achieved without the extensive reconstruction times that would be expected with larger FOV systems from processing their larger-sized files. Second, a re-stricted FOV reduces the volume examined, for which the practitioner is responsible to interpret. Hence, the tissues to be viewed can be merely the teeth and jaws, structures that the dentist should be able to comfortably interpret without submitting the data volume for an expert second opinion. Larger CBCT volume systems can include details of the cervical spine, soft tissue calcifications in the neck (such as carotid atherosclerosis), the ear, paranasal sinuses, orbits, calvarium, and brain. The dentist can be held responsible for detecting abnormalities in the examined volume. Interpretation is obviously much more complex when a larger volume of tissues is represented in the scan than when the FOV is tightly collimated to include only the dental structures.

Small FOV systems concentrate on the dental arches or individual temporomandibular joints, the structures most familiar to the average dentist. There is less detail of the cranial cavity, paranasal sinuses, ear, and neck—details less familiar to the average dentist and most likely to be interpreted by an oral and maxillofacial radiologist. High-resolution 3D imaging likely will be of special advantage to those planning or performing endodontic therapy (Figure 3), evaluating local periodontal structures (Figure 4a and Figure 4b), and planning dental implant cases limited to a small number of sites. These hybrid solutions are suitable for the orthodontist who wishes to continue with 2D cephalometry, but would like to have a more de-tailed 3D evaluation of impacted teeth. The small FOV also is suitable for assessing the relative 3D position of unerupted man-dibular third molars before minor oral surgical procedures.

A small FOV CBCT system is undoubtedly too restrictive for orthodontists desiring 3D cephalometry, maxillofacial surgeons who conduct craniofacial and orthognathic surgery, or for implantologists/prosthodontists performing complex procedures where the jaws and both temporomandibular joints are best evaluated in toto rather than as individual components. When making a purchase decision, the practitioner should consider carefully the proportions of work that require a small FOV vs those that need a larger FOV. Perhaps the small FOV/hybrid solution can be partnered with outsourcing cases requiring a larger FOV to an imaging laboratory, paired by having the larger FOV images read by an oral and maxillofacial radiologist to ensure that the patient receives a thorough inspection for unsuspected disease.

Third–Party Software and CBCT

The key feature of CBCT image output that makes the systems interoperable is the use of image files that are conformant with the Digital Imaging and Communications in Medicine standard (DICOM v3). This is the International Organization for Standardization (ISO) referenced standard for all diagnostic imaging including medical, dental, and veterinary imaging, and including all modalities such as x-ray, visible light, and ultrasound. In the January 2008 issue, the article, “Education in the Round: Multidimensional Imaging in Dentistry,” demonstrated the fusion of DICOM image files from 3D visible light photography and CBCT datasets made using a variety of systems. The use of DICOM image files took several years of demonstration and interactivity between vendors participating in DICOM WG 22 (Dentistry) and the ADA Standards Committee on Dental Informatics WG 12.1. Although it is now available from most top vendors, it is still necessary to ask the vendor for DICOM conformance, or a non-conformant product could be purchased accidentally. Most vendors have accepted that to be non-DICOM conformant is to be a non-starter commercially, because non-conformance would preclude the many necessary adjunctive services using third-party software. CBCT is a different matter.

While the software provided with CBCT systems is perfectly adequate for diagnostic purposes, most users of CBCT systems use additional software for dental implant planning, orthodontic planning, and orthognathic surgery planning. And increasingly, these third-party software “add-ons” specifically require DICOM files with appropriate header fields. Examples of such add-ons include implant planning software as Easy-Guide (Keystone Dental, Burlington, MA), SimPlant® (Materialise Dental Inc, Glen Burnie, MD), and Procera® (Nobel Biocare USA, LLC, Yorba Linda, CA), among others. Examples of orthodontic planning software include Dolphin 3D (Dolphin Imaging and Management Solutions, Chatsworth, CA) and InVivoDental™ (Anatomage Inc, San Jose, CA), among others (Figure 5a, Figure 5b, Figure 5c and Figure 5d).

Software will ultimately drive 3D dental imaging into the general dental market. The merging of image files and diagnostic and planning applications will significantly enhance the dentist’s ability to communicate, educate, and motivate patients to proceed with needed care.

CBCT Continues to Be a Major Focus Nationally

At this year’s ADA Annual Session, the CBCT demonstration will include six CBCT systems operating behind an expanded set of leaded panels at the entrance to the commercial exhibit hall. There will be rotating 30-minute presentations throughout the commercial exhibit times with continuing education credit hours available for dentists. This high-tech entrance to the exhibit hall will be accompanied by a seven-laser operatory area and computer-aided design/computer-aided manufacture (CAD/CAM) center. A DICOM-interoperability booth sponsored by the vendor participants in the ADA Standards Committee on Dental Informatics WG 12.1 will present third-party software working with images made at the meeting and from selected databases. This booth will demonstrate all aspects of digital image interoperability from the intraoral radiograph to CBCT and image fusion.

Conclusion

The world of 3D imaging for dentistry is continuing to evolve. Initially, the systems available were aimed at dental specialties requiring full maxillofacial FOV—namely orthodontics and oral surgery. By virtue of the cost of the large sensors used, the price was perhaps higher than many dental offices could afford. This led to increasing numbers of imaging centers and shared facilities around the United States. Further, the full-FOV systems imaged structures unfamiliar to many dentists. Under these circumstances, there is a need for backup with expert evaluation of the imaged tissue volumes.

These large FOV systems are still needed for orthodontists and oral surgeons, as well as for advanced reconstruction of the teeth or dental implants that require total gnathology assessment. Nonetheless, many dentists and dental specialists can use a more restricted FOV for their purposes. Where this is the case, the more affordable, smaller FOV—hybrid or otherwise—with a panoramic system may make sense. The higher resolution that is practical with such units makes them more useful for such purposes as endodontics. There is also the advantage of less need for an expert second opinion when the tissues imaged are restricted more narrowly to familiar dental structures.

Disclosure

Dr. Chenin is an employee of Anatomage, Inc.

About the Authors

Allan G. Farman, BDS, PhD, DSc, MBA
Professor of Radiology and Imaging Sciences
Department of Surgical and Hospital Dentistry
University of Louisville
Louisville, Kentucky

Diagnostic Maxillofacial Imaging University Associates
Louisville, Kentucky

Claudio M. Levato, DDS
Private Practice
Bloomingdale, Illinois

William C. Scarfe, BDS, FRACDS, MS
Professor of Radiology and Imaging Sciences
Department of Surgical and Hospital Dentistry
University of Louisville
Louisville, Kentucky

Diagnostic Maxillofacial Imaging University Associates
Louisville, Kentucky

Doug Chenin, DDS
Clinical Director
Anatomage Inc
San Jose, California

Adjunct Faculty
Orthodontics Department
University of the Pacific School of Dentistry
San Francisco, California