title: Reduced iodine load at CT pulmonary angiography with dual-energy monochromatic imaging: comparison with standard CT pulmonary angiography--a prospective randomized trial.
abstract: OBJECTIVE
  To compare quantitative and subjective image quality and radiation dose between standard computed tomographic (CT) pulmonary angiography (CTPA) and CTPA with a dual-energy technique with reduced iodine load.
  
  
  METHODS
  This prospective study was approved by the institutional review board and each participant provided informed consent. Ninety-four patients (59% male; mean age ± standard deviation, 62 years ± 15) were randomized to one of two protocols: standard CTPA (100-120 kVp) with standard contrast medium injection (n = 46) and dual-energy CTPA (image reconstruction at 50 keV) with the same injection volume as in the standard protocol but composed of contrast medium and saline in a 1:1 fashion, resulting in 50% reduction in iodine load (n = 48). Signal intensity and noise in three central and two segmental pulmonary arteries were measured; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. A five-point scale was used to subjectively evaluate vascular enhancement and image noise. The proportion of diagnostic (score, ≥ 3) studies and the interreader agreement regarding the dichotomized diagnostic versus nondiagnostic scale were compared between the two groups.
  
  
  RESULTS
  Compared with standard CTPA, dual-energy CTPA demonstrated higher signal intensity in all pulmonary arteries (all P < .01), inferior noise only in segmental arteries (P < .05), higher SNR and CNR (both P < .05), and compatible effective dose (P > .05). The five-point score was higher in the standard CTPA protocol (P < .05). The interreader agreement regarding the dichotomized diagnostic versus nondiagnostic scale was similar (P > .05) between the two groups.
  
  
  CONCLUSIONS
  Dual-energy CTPA with image reconstruction at 50 keV allows a significant reduction in iodine load while improving intravascular signal intensity, maintaining SNR and with comparable radiation dose.
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard St, Vancouver, BC, Canada.
authors.forename: Ren
authors.initials: R
authors.lastname: Yuan
authors.forename: William P
authors.initials: WP
authors.lastname: Shuman
authors.forename: James P
authors.initials: JP
authors.lastname: Earls
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Hague
authors.forename: Hina A
authors.initials: HA
authors.lastname: Mumtaz
authors.forename: Andrew
authors.initials: A
authors.lastname: Scott-Moncrieff
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Ellis
authors.forename: John R
authors.initials: JR
authors.lastname: Mayo
authors.forename: Jonathon A
authors.initials: JA
authors.lastname: Leipsic
mesh_terms: D000792:Angiography / Q000379:methods*; D016009:Chi-Square Distribution; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids / Q000008:administration & dosage*
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C054871:ioversol