title: Organ-based dose current modulation and thyroid shields: techniques of radiation dose reduction for neck CT.
abstract: OBJECTIVE
  The purpose of this study was to assess the difference in absorbed organ dose and image quality for MDCT neck protocols using automatic tube current modulation alone compared with organ-based dose modulation and in-plane thyroid bismuth shielding.
  
  
  METHODS
  An anthropomorphic female phantom with metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned on a 64-MDCT scanner. The protocols included a reference neck CT protocol using automatic tube current modulation and three modified protocols: organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield. Image noise was evaluated quantitatively with the SD of the attenuation value, and subjectively by two neuroradiologists.
  
  
  RESULTS
  Organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield protocols reduced the thyroid dose by 28%, 33%, and 45%, respectively, compared with the use of automatic tube current modulation alone (p ≤ 0.005). Organ-based dose modulation also reduced the radiation dose to the ocular lens (33-47%) compared with the use of automatic tube current modulation (p ≤ 0.04). There was no significant difference in measured noise and subjective image quality between the protocols.
  
  
  CONCLUSIONS
  Both organ-based dose modulation and thyroid shields significantly reduce the thyroid organ dose without degradation of subjective image quality compared with automatic tube current modulation. Organ-based dose modulation has the additional benefit of dose reduction to the ocular lens.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA. jennykh@gmail.com
authors.forename: Jenny K
authors.initials: JK
authors.lastname: Hoang
authors.forename: Terry T
authors.initials: TT
authors.lastname: Yoshizumi
authors.forename: Kingshuk Roy
authors.initials: KR
authors.lastname: Choudhury
authors.forename: Giao B
authors.initials: GB
authors.lastname: Nguyen
authors.forename: Greta
authors.initials: G
authors.lastname: Toncheva
authors.forename: Andreia R
authors.initials: AR
authors.lastname: Gafton
authors.forename: James D
authors.initials: JD
authors.lastname: Eastwood
authors.forename: Carolyn
authors.initials: C
authors.lastname: Lowry
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Hurwitz
mesh_terms: D001822:Body Burden; D005260:Female; D006801:Humans; D009333:Neck; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation*; D011874:Radiometry; D012984:Software; D013961:Thyroid Gland / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed