title: Radiation dose optimization in pediatric temporal bone computed tomography: influence of tube tension on image contrast and image quality.
abstract: BACKGROUND
  The purpose of this experimental study was to investigate the effect of tube tension reduction on image contrast and image quality in pediatric temporal bone computed tomography (CT).
  
  
  METHODS
  Seven lamb heads with infant-equivalent sizes were scanned repeatedly, using four tube tensions from 140 to 80 kV while the CT-Dose Index (CTDI) was held constant. Scanning was repeated with four CTDI values from 30 to 3 mGy. Image contrast was calculated for the middle ear as the Hounsfield unit (HU) difference between bone and air and for the inner ear as the HU difference between bone and fluid. The influence of tube tension on high-contrast detail delineation was evaluated using a phantom. The subjective image quality of eight middle and inner ear structures was assessed using a 4-point scale (scores 1-2 = insufficient; scores 3-4 = sufficient).
  
  
  RESULTS
  Middle and inner ear contrast showed a near linear increase with tube tension reduction (r = -0.94/-0.88) and was highest at 80 kV. Tube tension had no influence on spatial resolution. Subjective image quality analysis showed significantly better scoring at lower tube tensions, with highest image quality at 80 kV. However, image quality improvement was most relevant for low-dose scans.
  
  
  CONCLUSIONS
  Image contrast in the temporal bone is significantly higher at low tube tensions, leading to a better subjective image quality. Highest contrast and best quality were found at 80 kV. This image quality improvement might be utilized to further reduce the radiation dose in pediatric low-dose CT protocols.
authors.affiliation: Institute of Diagnostic and Interventional Neuroradiology, University Hospital Berne, Berne, Switzerland. claudenauer@hotmail.com
authors.forename: Claude Bertrand
authors.initials: CB
authors.lastname: Nauer
authors.forename: Christoph
authors.initials: C
authors.lastname: Zubler
authors.forename: Christian
authors.initials: C
authors.lastname: Weisstanner
authors.forename: Christof
authors.initials: C
authors.lastname: Stieger
authors.forename: Pascal
authors.initials: P
authors.lastname: Senn
authors.forename: Andreas
authors.initials: A
authors.lastname: Arnold
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D066298:In Vitro Techniques; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012756:Sheep; D013701:Temporal Bone / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000592:standards*