title: The effects of bismuth breast shields in conjunction with automatic tube current modulation in CT imaging.
abstract: BACKGROUND
  There are mechanisms within CT scanners and shielding that can be used to lower dose to patients.
  
  
  OBJECTIVE
  The objective of our study was to evaluate the dose changes and image quality with and without a breast shield for multidetector CT of the chest with angular tube current modulation.
  
  
  METHODS
  An anthropomorphic 5-year-old phantom was scanned with and without bismuth breast shielding and with and without angular tube current modulation. Image quality was assessed by measuring signal-to-noise ratio and contrast-to-noise ratio as well as measuring qualitatively. ANOVA single-factor p-value analysis of paired datasets was used for the statistical analysis.
  
  
  RESULTS
  The breast shielding and angular tube current modulation resulted in a dose reduction to 85% for the breast and 90% overall. Although no qualitative differences were noted with and without the breast shielding used with angular tube current modulation, there were statistically significant differences in the contrast-to-noise ratio and CT numbers.
  
  
  CONCLUSIONS
  When used with angular tube current modulation, breast shields influence the contrast-to-noise ratio and CT numbers, and therefore should not be used for chest CT. Greater dose reduction can be obtained by reducing the reference mAs (or reference noise index).
authors.affiliation: Department of Radiology, The Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA, 19104, USA, servaes@email.chop.edu.
authors.forename: Sabah
authors.initials: S
authors.lastname: Servaes
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhu
mesh_terms: D001729:Bismuth / Q000528:radiation effects*; D001822:Body Burden; D001940:Breast / Q000528:radiation effects*; D002675:Child, Preschool; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D019047:Phantoms, Imaging; D011482:Protective Devices; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D011874:Radiometry; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*
chemical_list: D001729:Bismuth