The advantages of CBCT

May 1, 2011
An interview with Dr. David Hatcher

An interview with Dr. David Hatcher

By Dr. David Gane

For more on this topic, go to www.dentaleconomics.com and search using the following key words: 3-D technology, CBCT, fourth dimension, Dr. David Gane, Dr. David Hatcher.

Cone beam computer tomography is a game changing imaging technology that promises to transform the way we diagnose and treat many dental conditions. Dr. David Hatcher is a well-known oral and maxillofacial radiologist who has dedicated his career to advanced imaging techniques and technology and is a wealth of knowledge and information on the topic of cone beam computed tomography.

Dr. David Gane: David, I believe you were one of the first, if not the very first, to adopt CBCT technology in the U.S. Why did you jump in so early, and how has the technology evolved over the last decade?

Dr. David Hatcher: Our group, DDI, had our first two NewTom cone beam units installed in May 2001. Loma Linda preceded us by a day and was the first North American Cone Beam installation. DDI uses advanced technology when appropriate, and provides imaging services for our community. DDI was fortunate to have been asked to assist NewTom in acquiring the FDA 510K approval for their machines, and this allowed us advance notice of the technology. DDI recognized the value of cone beam technology for clinical investigations and was eager to share this with our referral sources.

CBCT has evolved in every imaginable way since its introduction into the U.S. In 2001 the sole provider of CBCT technology for dentistry was QR of Italy, which produced the NewTom 9000. Since then, NewTom has gone through several generational changes. The sensors have changed from an image intensifier to a flat panel. The flat panel sensors have allowed for a reduction in the machine footprint size, improvement in signal to noise ratio (quality), and X-ray collimation abilities. Today there are several manufacturers of cone beam units and may be as many as 40 different models. CBCT units produce the image volume, but it is the software that allows us to visualize the anatomy. The software development for CBCT has evolved at a phenomenal pace and has allowed users to exploit the output from the CBCT units.

Gane: CBCT adoption is on the rise globally. What is driving this, and do you think CBCT will ever completely replace 2-D dental radiography?

Hatcher: I do not know all that drives the adoption of this technology, but the first things that pop into my mind include education, knowledge, and research. Once you get past the cool factor of CBCT and 3-D display, you’re left with the diagnostic value of the study. The research process allows for a systematic validation of CBCT technology for specific clinical applications. CBCT needs to provide uniquely useful information and be obtainable at an acceptable risk and cost. The alternatives for CBCT include the traditional 2-D imaging, and I suspect it will have a useful life for quite some time. CBCT should not be used if traditional 2-D imaging answers the clinical question and meets the criteria of lower risk and cost.

Gane: There is a large variety of CBCT systems. Do you see any emerging trends with respect to which types will best serve the profession and patients?

Hatcher: The trends I have observed include design variables that involve the sensor types, field of view, dose per study, scan resolution, scan times, native software, and cost. Most of the current CBCT units have evolved to a flat panel sensor, which allows the manufacturers to scale the sensor size to match the anticipated applications of the end users, keep the machine footprint as small as possible, and manage the cost of the unit. There is a range of sensor types to choose from. At one end of the scale is a small sensor with a high sampling frequency that may be very useful for investigating tooth anatomy, and at the other end would be a large sensor for imaging the entire maxillofacial complex in a single session.

Gane: From your perspective, what type of risk management challenges come with owning a CBCT? What are the main issues as you see them?

Hatcher: The first challenge that comes to mind is establishing criteria for when it is indicated to use a CBCT in place of traditional 2-D imaging. Clinicians are being reminded that CBCT is preferable to 2-D imaging for selected applications, including impaction localization and assessment of implant sites to help avoid anatomic hazards. The next challenge is to design and implement imaging protocols for the clinical investigation. The imaging protocol will provide the optimum image volume that will facilitate the downstream clinical decisions.

Gane: Once the CBCT data is acquired, what are clinicians’ professional responsibility with respect to interpretation and reporting? Can they do this themselves or do they have to recruit the services of an oral maxillofacial radiologist (OMFR)?

Hatcher: All volumes need to be evaluated to identify or rule out the presence of pathosis. It has been estimated that there are approximately 3,000 CBCT units in the U.S. I do not believe there are enough available OMFR to evaluate all of the scans being generated. I would expect that an owner of a CBCT unit with proper education and experience could assume the responsibility of reviewing his or her own CBCT volumes and request assistance from an OMFR as needed.

Gane: If the services of an OMFR are obtained, is it required that the radiologist be licensed in the same state as that in which the CBCT was acquired? Or can an out of jurisdiction radiologist be used as a second opinion?

Hatcher: It is a very common practice for OMFRs to perform an “over read” and provide second opinions, even on cases generated outside their region of licensure.

Gane:What are the most common incidental findings that you report on in your practice?

Hatcher: I have not tabulated occurrences of incidental findings, but the types of pathosis I observe include inflammatory lesions associated with nonvital teeth, inflammatory sinus disease, and TMJ degenerative joint disease.

Gane:If a dentist notes a suspicious finding in a region of the image outside of the jaws, can the dentist be expected to make a radiographic diagnosis outside the scope of his or her license? What is their duty in this scenario?

Hatcher: I have seen this question addressed by plaintiff and defense attorneys. The plaintiff attorneys tend to give a greater responsibility to the dentist to identify and deal with abnormalities outside the jaws than do the defense attorneys. I have observed that the defense and plaintiff attorneys suggest that dual degree dentists (DDS/MD) may have no anatomic limitations with respect to liability. I believe it is good practice to review the entire volume for abnormalities.

Gane:Would you say that taking a CBCT is the standard of care for at least some dental treatments? If not, when will CBCT become the standard of care?

Hatcher:It is my understanding that the standard of care is determined by each dental specialty or dental group, and I am not aware that any specialty groups have declared CBCT as a standard of care. I have observed that certain types of litigated cases are getting more difficult to defend when CBCT has not been employed for planning. Examples of these cases include nerve injury, secondary to implant placement, or tooth removal.

Gane:What do you think is the single most important thing a CBCT owner can do to minimize risk when obtaining or ordering a CBCT data set?

Hatcher: Design an imaging process that follows this outline: 1) determine the need for imaging for each case; 2) design case-specific imaging goals; 3) select an imaging modality that satisfies the imaging goals and has an acceptable risk and cost; 4) select the optimum imaging protocol, including field of view to match area of interest and resolution; and 5) evaluate the images.

Gane: There seems to be a growing need for CBCT education and guidance. Where can one learn more about CBCT, when to use it, and the best practices for its use?

Hatcher: The CBCT educational process is currently inefficient and seems to be lagging behind the technology development. This is sad and results in underperformance. There are several resources, including textbooks, journal publications, and scientific meetings. There are almost no “hands-on courses” that address machine operation, software manipulation, and case review. A few of the CBCT and software companies organize educational meetings.

Gane:What about the fourth dimension? When can we expect that to arrive?

Hatcher:The fourth dimension involves time. The fourth dimension for CBCT could be described as a timed sequence of 3-D images. In this scenario, the various time points need to be managed using a common Cartesian coordinate system over time. When the time sampling intervals are short, there is the opportunity to visualize and measure jaw motion, articulation, and facial expression. When the time interval samples are extended, then outcomes assessment can be performed. The fourth dimension is currently available but requires the use of third-party software or hardware.

David C. Hatcher, DDS, MSc, MRCD(c), has a specialty degree and MSc in oral and maxillofacial radiology from the University of Toronto and was an associate professor and chairman of the Division of Radiology at University of Alberta, Canada. Dr. Hatcher is in private OMFR practice in Sacramento, Calif., and has faculty appointments at the University of Southern Nevada, University of California San Francisco, and the University of Pacific Dental Schools. Contact him at [email protected].

Dr. David Gane has a passion for dental imaging and has published and lectured both nationally and internationally on this topic. Dr. Gane serves as vice president of Dental Imaging for Carestream Dental LLC, the exclusive maker of Kodak Dental Systems. Reach Dr. Gane at [email protected].

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