title: Contrast monitoring techniques in CT pulmonary angiography: An important and underappreciated contributor to breast dose.
abstract: OBJECTIVE
  The aims of our study were to evaluate the contribution of contrast-monitoring techniques to breast dose in pregnant and non-pregnant women, and to investigate the effect of a reduced peak kilovoltage (kV) monitoring scan protocol on breast dose and Computed Tomography Pulmonary Angiography (CTPA) diagnostic quality.
  
  
  METHODS
  Single center retrospective study of 221 female patients undergoing a reduced kV 80kV contrast-monitoring CTPA protocol compared to 281 patients using the conventional 120kV contrast-monitoring protocol (Siemens Somatom Definition AS+). 99 pregnant patients analyzed separately. ImPACT dosimetry software was used to calculate dose. Group subsets were evaluated to assess CTPA diagnostic quality.
  
  
  RESULTS
  The contrast-monitoring component of a CTPA study constituted 27% of the overall breast dose when using a standard 120kV protocol compared to only 7% of the overall breast dose in the 80kV study group. The dose to the breast from the contrast-monitoring component alone was reduced by 79% in the non-pregnant patients (0.36mGy±0.37 versus 1.7mGy±1.02; p<0.001), and by 88% in the pregnant population (0.25mGy±0.67 versus 2.24mGy±1.61; p<0.001). There was no statistical difference in CTPA diagnostic quality or timing.
  
  
  CONCLUSIONS
  Despite a short scan length and relatively small DLP, contrast-monitoring techniques (test-bolus or bolus-tracked) set at 120kV can account for 27% of the overall breast dose accrued from a CTPA study. By decreasing the kilovoltage of the contrast-monitoring component, a significant reduction in breast dose for pregnant and non-pregnant female patients can be achieved without affecting CTPA quality or timing.
authors.affiliation: Department of Radiology, Whitty Building, North Circular Road, Mater Misericordiae University Hospital, Dublin 7, Ireland. Electronic address: dpmmitchell@gmail.com.
authors.forename: D P
authors.initials: DP
authors.lastname: Mitchell
authors.affiliation: Department of Radiology, Whitty Building, North Circular Road, Mater Misericordiae University Hospital, Dublin 7, Ireland. Electronic address: mrowan@mater.ie.
authors.forename: M
authors.initials: M
authors.lastname: Rowan
authors.affiliation: Department of Radiology, Whitty Building, North Circular Road, Mater Misericordiae University Hospital, Dublin 7, Ireland. Electronic address: eloughman@mater.ie.
authors.forename: E
authors.initials: E
authors.lastname: Loughman
authors.affiliation: Department of Radiology, Whitty Building, North Circular Road, Mater Misericordiae University Hospital, Dublin 7, Ireland. Electronic address: cridge@mater.ie.
authors.forename: C A
authors.initials: CA
authors.lastname: Ridge
authors.affiliation: Department of Radiology, Whitty Building, North Circular Road, Mater Misericordiae University Hospital, Dublin 7, Ireland. Electronic address: pmacmahon@mater.ie.
authors.forename: P J
authors.initials: PJ
authors.lastname: MacMahon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000187:drug effects*; D000072226:Computed Tomography Angiography / Q000379:methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011874:Radiometry; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult
keywords: Breast organ dose; CT pulmonary angiography; Pulmonary embolus; Radiation dose