title: Dual-energy CT Aortography with 50% Reduced Iodine Dose Versus Single-energy CT Aortography with Standard Iodine Dose.
abstract: OBJECTIVE
  Because many patients with aortic pathology also have compromised renal function, we wished to investigate dual-energy computed tomography (DECT) aortography with 50% reduced iodine dose compared to single-energy computed tomography (SECT) aortography with standard iodine dose.
  
  
  METHODS
  Fifty patients had DECT aortography with 50% reduced iodine dose. Thirty-four of these patients had prior SECT aortography with standard iodine dose. DECT images were reconstructed at both 50 and 77 keV and were compared to SECT 120 kVp images. Reviewers measured aortic attenuation, image noise, and scored vascular enhancement. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated. Volume CT dose index was recorded.
  
  
  RESULTS
  Mean iodine dose was 47 g for SECT and 24 g for DECT. Aortic attenuation was highest at reduced iodine dose DECT 50 keV (570 ± 105 Hounsfield units [HU]) compared to 77 keV (239 ± 40 HU) or to standard iodine dose SECT 120 kVp (356 ± 69 HU) (P < 0.05). Image noise was greatest at 50 keV compared to 77 keV and 120 kVp (P < 0.05) but was similar between 77 keV and 120 kVp (P > 0.05). SNR and CNR were the same at 50 keV and 120 kVp (P > 0.05). Mean vascular enhancement scores were all above 3.0 (good, typical enhancement). Volume CT dose index was 11.7 mGy for DECT and 11.8 mGy for SECT (P = 0.37).
  
  
  CONCLUSIONS
  DECT aortography with 50% reduced iodine reconstructed at 50 keV resulted in significantly greater aortic attenuation, good subjective vascular enhancement, and comparable SNR and CNR compared to standard iodine dose SECT. DECT image noise at 77 keV was similar to SECT at 120 kVp.
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195. Electronic address: wshuman@uw.edu.
authors.forename: William P
authors.initials: WP
authors.lastname: Shuman
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195.
authors.forename: Keith T
authors.initials: KT
authors.lastname: Chan
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Busey
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Mitsumori
authors.affiliation: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195.
authors.forename: Kent M
authors.initials: KM
authors.lastname: Koprowicz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001011:Aorta / Q000000981:diagnostic imaging; D001027:Aortography / Q000379:methods*; D000072226:Computed Tomography Angiography / Q000379:methods*; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007455:Iodine / Q000008:administration & dosage*; D007472:Iohexol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D059629:Signal-To-Noise Ratio; D014283:Triiodobenzoic Acids / Q000008:administration & dosage
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; D007472:Iohexol; D007455:Iodine; C044834:iodixanol
keywords: Computed tomography; aortography; contrast media; dual energy