title: Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography.
abstract: BACKGROUND
  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° rotation, 600 image frames, 120 kV[p], 5 mA, 7.4 seconds), standard (360°, 300 frames, 120 kV[p], 5 mA, 3.7 seconds), QuickScan (180°, 160 frames, 120 kV[p], 5 mA, 2 seconds), and QuickScan+ (180°, 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 × 16-cm cephalometric fields of view ranged from 11 to 85 μSv in the adult phantom and 18 to 120 μSv 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.
authors.affiliation: Professor, Department of Diagnostic Sciences, School of Dentistry, University of North Carolina, Chapel Hill, NC. Electronic address: jbl@email.unc.edu.
authors.forename: John B
authors.initials: JB
authors.lastname: Ludlow
authors.forename: Cameron
authors.initials: C
authors.lastname: Walker
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002508:Cephalometry; D002648:Child; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D009970:Orthodontics / Q000295:instrumentation* / Q000379:methods; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*