Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography

Introduction: The increasing use of cone-beam computed tomography in orthodontics has been coupled with heightened concern about the long-term risks of x-ray exposure in orthodontic populations. An industry response to this has been to offer low-exposure alternative scanning options in newer cone-beam computed tomography models. Methods: Effective doses resulting from various combinations of field of view size and field location comparing child and adult anthropomorphic phantoms with the recently introduced i-CAT FLX cone-beam computed tomography unit (Imaging Sciences, Hatfield, Pa) were measured with optical stimulated dosimetry using previously validated protocols. Scan protocols included high resolution (360 degrees rotation, 600 image frames, 120 kV[p], 5 mA, 7.4 seconds), standard (360 degrees, 300 frames, 120 kV[p], 5 mA, 3.7 seconds), QuickScan (180 degrees, 160 frames, 120 kV[p], 5 mA, 2 seconds), and QuickScan+ (180 degrees, 160 frames, 90 kV[p], 3 mA, 2 seconds). Contrast-to-noise ratio was calculated as a quantitative measure of image quality for the various exposure options using the QUART DVT phantom. Results: Child phantom doses were on average 36% greater than adult phantom doses. QuickScan+ protocols resulted in significantly lower doses than standard protocols for the child (P = 0.0167) and adult (P = 0.0055) phantoms. The 13 x 16(-)cm cephalometric fields of view ranged from 11 to 85 mu Sv in the adult phantom and 18 to 120 mu Sv in the child phantom for the QuickScan+ and standard protocols, respectively. The contrast-to-noise ratio was reduced by approximately two thirds when comparing QuickScan+ with standard exposure parameters. Conclusions: QuickScan+ effective doses are comparable with conventional panoramic examinations. Significant dose reductions are accompanied by significant reductions in image quality. However, this trade-off might be acceptable for certain diagnostic tasks such as interim assessment of treatment results.