Abstract
The use of cone beam computed tomography (CBCT) in dentistry has grown exponentially since its inception and that trend continues. Though CBCT has become routine to some, its popularity in dentistry only demonstrates that education in CBCT is needed now more than ever. This presentation covers key components to consider when purchasing a CBCT unit and describes concepts in interpretation and radiation safety.
When considering purchasing a CBCT unit, it is important to realize that the purchase is ongoing in the sense that both the software and hardware will require updates, upgrades, and replacements. Hardware and software technology advance over time and the technology has a lifespan. Management of software and hardware updates varies among vendors, but both are key in the final decision of which unit to purchase. Maintenance of the CBCT unit is essential and manufacturers of CBCT units are required to supply quality control (QC) phantoms with the unit.
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CBCT units differ on calibration and QC procedure frequency, but it is worth considering a manufacturer that provides sufficient support and can send a trained technician to complete this process for the CBCT unit. Manufacturer support (hardware and IT related) is invaluable to the consistent and proper function of the CBCT unit.Shielding design for radiation protection of office personnel and patients is crucial. According to the latest national council on radiation protection and measurements (NCRP) report for dentistry, report No. 177, the majority of states do not have specific requirements for dental CBCT systems.
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Some states consider CBCT to be a form of panoramic imaging while others view CBCT as a form of medical CT.1
According to Reid et al,2
the average stray radiation (scatter radiation emitted from the patient plus leakage radiation emitted from the X-ray unit) from panoramic imaging is 0.45 μGy per exposure. Because of the small amount of stray radiation, they concluded that no special environmental shielding barriers were necessary for that particular panoramic unit.2
When determining shielding for CBCT, it is necessary to use the highest option for exposure, which depends on patient size, field of view (FOV) size, and spatial resolution.3
Comparing the dose from panoramic imaging determined by Reid et al with one CBCT unit, it takes 20 panoramic radiographs to equal the same stray radiation exposure as one CBCT scan (stray radiation measurement of this particular CBCT unit verified by author). Though these exposure values are specific only to the units that were evaluated and cannot be applied universally, it is clear that CBCT stray radiation exposure can be considerably higher than stray radiation exposure from a panoramic unit. The amount of stray radiation will vary among units and should be measured and specified by the manufacturer. NCRP report 177 recommends installing CBCT units in a separate room rather than in an open space or alcove and monitoring office staff for the year following installation.1
Dosimeter monitoring can help ensure staff are not exposed to more than 0.02 mGy/week (non-occupationally exposed individuals) and 0.1 mGy/week (occupationally exposed individuals).1
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Though familiarity with these values is important, perhaps the easiest thing to do is ask a qualified expert to confirm that the office is adequately shielded for the CBCT unit.Before ordering CBCT imaging, as with 2-dimensional imaging, a thorough clinical examination should be completed along with a review of medical and dental histories and existing images.
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Position papers on the use of CBCT are available and are accessible through the American Academy of Oral and Maxillofacial Radiology (AAOMR) website (https://aaomr.org/position-papers/).6
, - Tyndall D.A.
- Price J.B.
- Tetradis S.
- et al.
Position statement of the American academy of oral and maxillofacial radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography.
Oral Surg Oral Med Oral Pathol Oral Radiol. 2012; 113: 817-826
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, 8
Artifacts in CBCT imaging can limit its utility for certain diagnostic tasks and likely contribute to the imperfect detection of vertical root fractures.9
Thin bone may not be visible on CBCT imaging and patient motion results in radiopaque streak artifacts.10
Software algorithms can be applied to the CBCT data at the time of reconstruction to reduce artifact formation; however, these software changes can alter the way hard tissue structures present in the image.Patient dose from CBCT varies significantly, as much as a factor of 10, among different CBCT units.
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The range of effective dose from CBCT imaging is 11 to 674 microSieverts (μSv) for medium FOV scans and 30 to 1073 μSv for large FOV scans.1
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These values are equivalent to 0.7 to 42 panoramic radiographs and 2 to 67 panoramic radiographs, respectively. These dose ranges do not reflect the increase in dose that would occur with high spatial resolution protocols or when imaging children.1
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Notably, however, low dose protocols are available on some CBCT units that can reduce the dose to the patient significantly. This ability is especially helpful for younger patients as they are more sensitive to radiation-induced cancer as well as patients that have difficulty holding still as the time to acquire the image is reduced considerably.12
CBCT is an invaluable tool for diagnosis and treatment planning in dentistry. Effective implementation of CBCT in practice requires knowledge of the CBCT hardware, software, dose protocols, data transmission, and artifact formation. Seeking the expertise of an oral and maxillofacial radiologist may be helpful for questions about incidental findings on CBCT as well as questions about the technology in general.
Acknowledgments
The author would like to recognize and sincerely thank the skilled communications crew at Augusta University, Mary Lirette, Rachel Carman, Kaeshon King, and Timothy Williams, for their help in recording and editing the video. The author would also like to recognize and sincerely thank Frank Brittingham for providing the music for the video. Lastly, the author would like to recognize and sincerely thank those that participated in the filming of the video: Dr Joshua Jernigan, Ms Amber Ezzyk, Dr Sajitha Kalathingal, Dr Elizabeth Schappell, and Mr Andrew Ogiba.
Supplementary data
References
- Radiation Protection in Dentistry and Oral & Maxillofacial Imaging.NCRP, 2019 (Report No. 177)
- Radiation exposures around a panoramic dental x-ray unit.Oral Surg Oral Med Oral Pathol. 1993; 75: 780-782
- Structural Shielding Design for Medical X-ray Imaging Facilities.NCRP, 2004 (Report No. 147)
- Radiation Protection in Dentistry.NCRP, 2003 (Report No. 145)
- The use of cone-beam computed tomography in dentistry. An advisory statement from the American dental association council on scientific affairs.JADA. 2012; 143: 899-902
- Position statement of the American academy of oral and maxillofacial radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography.Oral Surg Oral Med Oral Pathol Oral Radiol. 2012; 113: 817-826
- Clinical recommendations regarding use of cone beam computed tomography in orthodontics. position statement by the American Academy of oral and maxillofacial radiology.Oral Surg Oral Med Oral Pathol. 2013; 116: 238-257
- Use of cone beam computed tomography in endodontics 2015 update. AAE and AAOMR Joint Position Statement.Oral Surg Oral Med Oral Pathol Oral Radiol. 2015; 120: 508-512
- Detection of vertical root fractures by using cone-beam computed tomography: a clinical study.J Endod. 2011; 37: 768-772
- Accuracy of cone-beam computed tomography at different resolutions assessed on the bony covering of the mandibular anterior teeth.Am J Orthod Dentofacial Orthop. 2012; 141: 41-50
- Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography.Am J Orthod Dentofacial Orthop. 2013; 144: 802-817
- Effective dose of dental CBCT-a meta analysis of published data and additional data for nine CBCT units.Dentomaxillofac Radiol. 2015; 44: 20140197
- Correction to effective dose of dental CBCT--a meta analysis of published data and additional data for nine CBCT units.Dentomaxillofac Radiol. 2015; 44: 20159003
American Academy of Oral and Maxillofacial Radiolgy website. aaomr.org
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