title: Chest Computed Tomography Radiation Dose Optimization: Comparison of Automatic Exposure Control Strength Curves.
abstract: OBJECTIVE
  The aim of the study was to compare radiation dose and image quality between the "average" and the "very strong" automatic exposure control (AEC) strength curves.
  
  
  METHODS
  Images reconstructed with filtered back-projection techniques and radiation dose data of unenhanced helical chest computed tomography (CT) examinations obtained at 2 hospitals (hospital A, hospital B) using the same scanner devices and acquisition protocols but different AEC strength curves were evaluated over a 3-month period. The selected AEC strength curve applied to "slim" patients (diameter <32 cm estimated from the attenuation automatically measured on the topogram) was "average" and "very strong" in hospital A and hospital B, respectively. Two radiologists with 13 and 24 years of experience scored the image quality of the lung parenchyma and the mediastinum on a 5-point scale. The patients' effective diameter, the delivered CT dose index volume, and dose-length products were recorded.
  
  
  RESULTS
  A total of 410 patients were included. The average body mass index was 24.0 kg/m in hospital A and 24.8 kg/m in hospital B. There was no significant difference between hospitals with respect to age, sex ratio, weight, height, body mass index, effective diameters, and image quality scores for each radiologist (P ranging from 0.050 to 1.000). The mean CT dose index volume for the entire population was 2.0 mGy and was significantly lower in hospital B with the "very strong" AEC curve as compared with hospital A (-11%, P=0.001). The mean dose-length product delivered in this 70 kg-weight population was 68 mGy cm, corresponding to an effective dose of 0.95 mSv.
  
  
  CONCLUSIONS
  Changing the AEC strength curve from "average" to "very strong" for slim patients maintains image quality and reduces the radiation dose to <1 mSv in routine chest CT examinations reconstructed with filtered back-projection techniques.
authors.affiliation: *Department of Radiology, Epicura, Clinique Luis Caty, Baudour Departments of †Pneumology §Radiology, Hôpital Erasme, Brussels, Belgium ‡Department of Radiology, Clinique des Grangettes, Chêne-Bougeries, Switzerland.
authors.forename: Elodie
authors.initials: E
authors.lastname: Gyssels
authors.forename: Pascale
authors.initials: P
authors.lastname: Bohy
authors.forename: Arnaud
authors.initials: A
authors.lastname: Cornil
authors.forename: Alain
authors.initials: A
authors.lastname: van Muylem
authors.forename: Nigel
authors.initials: N
authors.lastname: Howarth
authors.forename: Pierre A
authors.initials: PA
authors.lastname: Gevenois
authors.forename: Denis
authors.initials: D
authors.lastname: Tack
mesh_terms: D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*