Dosimetry of a next generation i-CAT CBCT machine as compared to a digital panoramic and lateral cephalogram in patient diagnosis and treatment at the University of Minnesota Division of Orthodontics.

University of Minnesota M.S. thesis. October 2010. Major: Destistry. Advisor: Dr. Brent Larson. 1 computer file (PDF); vi, 32 pages.Background: Three-dimensional cone-beam computed tomography (CBCT) has rapidly gained prominence and exposure in the dental community over the last few years, and is quickly becoming the routine imaging modality for many orthodontic clinics. However, questions remain about the amount of radiation patients are exposed to during the multiple scans needed for the associated advanced diagnostic and treatment techniques. Objective: To determine the amount of radiation potentially absorbed by a patient during routine orthodontic imaging with the Next Generation i-CAT® cone-beam computed tomography machine with various scan settings. Also, to evaluate the amount of radiation patients at the University of Minnesota Division of Orthodontics are exposed to during a routine two-year treatment including cone-beam scans for diagnosis and for SureSmile® treatment. Methods: Twenty-four thermoluminescent dosimeters placed at anatomic sites inside a RANDO® phantom were scanned using various scan protocols on a Next Generation i- CAT machine and digital panoramic and cephalometric xray machine. Effective doses were calculated using the 2007 International Commission on Radiological Protection recommended tissue weighting factors. Results: The effective doses ranged from 108-129mSv for standard resolution CBCT scans at various voxel size and field of view settings; 196-212mSv for enhanced or highresolution full field of view scans; and measured 252mSv for a high-resolution landscape scan as would be used for SureSmile® therapy. Digital panoramic xray dose was 39mSv and lateral cephalogram was 25mSv. Discussion: Cone-beam CT, while providing proven diagnostic and therapeutic benefits, also exposes patients to a higher level of radiation than with standard digital 2D examinations. It is important for the clinician to weigh the benefits against the risks when determining their imaging protocol