title: CT dose reduction using Automatic Exposure Control and iterative reconstruction: A chest paediatric phantoms study.
abstract: OBJECTIVE
  To evaluate the impact of Automatic Exposure Control (AEC) on radiation dose and image quality in paediatric chest scans (MDCT), with or without iterative reconstruction (IR).
  
  
  METHODS
  Three anthropomorphic phantoms representing children aged one, five and 10-year-old were explored using AEC system (CARE Dose 4D) with five modulation strength options. For each phantom, six acquisitions were carried out: one with fixed mAs (without AEC) and five each with different modulation strength. Raw data were reconstructed with Filtered Back Projection (FBP) and with two distinct levels of IR using soft and strong kernels. Dose reduction and image quality indices (Noise, SNR, CNR) were measured in lung and soft tissues. Noise Power Spectrum (NPS) was evaluated with a Catphan 600 phantom.
  
  
  RESULTS
  The use of AEC produced a significant dose reduction (p<0.01) for all anthropomorphic sizes employed. According to the modulation strength applied, dose delivered was reduced from 43% to 91%. This pattern led to significantly increased noise (p<0.01) and reduced SNR and CNR (p<0.01). However, IR was able to improve these indices. The use of AEC/IR preserved image quality indices with a lower dose delivered. Doses were reduced from 39% to 58% for the one-year-old phantom, from 46% to 63% for the five-year-old phantom, and from 58% to 74% for the 10-year-old phantom. In addition, AEC/IR changed the patterns of NPS curves in amplitude and in spatial frequency.
  
  
  CONCLUSIONS
  In chest paediatric MDCT, the use of AEC with IR allows one to obtain a significant dose reduction while maintaining constant image quality indices.
authors.affiliation: Department of Radiology, Nîmes University Hospital, Medical Imaging Group Nîmes, EA 2415, Bd Prof Robert Debré, 30029 Nîmes Cedex, France. Electronic address: joel.greffier@chu-nimes.fr.
authors.forename: Joël
authors.initials: J
authors.lastname: Greffier
authors.affiliation: Department of Radiology, Nîmes University Hospital, Medical Imaging Group Nîmes, EA 2415, Bd Prof Robert Debré, 30029 Nîmes Cedex, France. Electronic address: fabricio.pereira@chu-nimes.fr.
authors.forename: Fabricio
authors.initials: F
authors.lastname: Pereira
authors.affiliation: Department of Radiology, Nîmes University Hospital, Medical Imaging Group Nîmes, EA 2415, Bd Prof Robert Debré, 30029 Nîmes Cedex, France. Electronic address: francesco.macri@chu-nimes.fr.
authors.forename: Francesco
authors.initials: F
authors.lastname: Macri
authors.affiliation: Department of Radiology, Nîmes University Hospital, Medical Imaging Group Nîmes, EA 2415, Bd Prof Robert Debré, 30029 Nîmes Cedex, France. Electronic address: jean.paul.beregi@chu-nimes.fr.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Beregi
authors.affiliation: Department of Radiology, Nîmes University Hospital, Medical Imaging Group Nîmes, EA 2415, Bd Prof Robert Debré, 30029 Nîmes Cedex, France. Electronic address: ahmed.larbi@chu-nimes.fr.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Larbi
mesh_terms: D002648:Child; D002675:Child, Preschool; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D007223:Infant; D061330:Multidetector Computed Tomography / Q000295:instrumentation* / Q000379:methods*; D010372:Pediatrics / Q000295:instrumentation / Q000379:methods; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods
keywords: Automatic Exposure Control; Children; Iterative reconstruction; MDCT; Radiation dose