Original Paper| Volume 32, ISSUE 4, P582-589, April 2016

CT dose reduction using Automatic Exposure Control and iterative reconstruction: A chest paediatric phantoms study

Published:April 04, 2016DOI:


      • Automatic Exposure Control (AEC) reduces dose delivered in chest paediatric MDCT.
      • Application of AEC results in a deterioration of image quality indices.
      • Iterative reconstruction (IR) compensates for the deterioration of image quality indices.
      • IR changes the amplitude and the spatial frequency in Noise Power Spectrum curves.
      • AEC/IR reduce the dose by 43–91% while maintaining diagnostic image quality.



      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).


      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.


      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.


      In chest paediatric MDCT, the use of AEC with IR allows one to obtain a significant dose reduction while maintaining constant image quality indices.


      AEC (Automatic Exposure Control), CNR (contrast-to-noise ratio), CTDIvol (volume CT dose index), DRLs (Diagnostic Reference Levels), FBP (Filtered Back Projection), IR (iterative reconstruction), mAseff (effective or modulated mAs), mAsfix (fixed mAs), mAsmod (modulated mAs), mAsref (image quality reference mAs), MDCT (Multi Detector Computed Tomography), NPS (Noise Power Spectrum), ROI (Region of Interest), SAFIRE (Sinogram Affirmed Iterative Reconstruction), SNR (signal-to-noise ratio), SSDE (size-specific dose estimate)


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Physica Medica: European Journal of Medical Physics
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Brenner D.J.
        • Hall E.J.
        Computed tomography–an increasing source of radiation exposure.
        N Engl J Med. 2007; 357: 2277-2284
        • UNSCEAR 2000 published
        United Nations Scientific Committee on the effects of atomic radiation.
        Health Phys. 2001; 80: 291
        • Brenner D.
        • Elliston C.
        • Hall E.
        • Berdon W.
        Estimated risks of radiation-induced fatal cancer from pediatric CT.
        AJR Am J Roentgenol. 2001; 176: 289-296
        • Pearce M.S.
        • Salotti J.A.
        • Little M.P.
        • McHugh K.
        • Lee C.
        • Kim K.P.
        • et al.
        Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study.
        Lancet. 2012; 380: 499-505
        • Mathews J.D.
        • Forsythe A.V.
        • Brady Z.
        • Butler M.W.
        • Goergen S.K.
        • Byrnes G.B.
        • et al.
        Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians.
        BMJ. 2013; 346: f2360
        • Vock P.
        CT dose reduction in children.
        Eur Radiol. 2005; 15: 2330-2340
        • Donnelly L.F.
        Reducing radiation dose associated with pediatric CT by decreasing unnecessary examinations.
        AJR Am J Roentgenol. 2005; 184: 655-657
        • Brody A.S.
        • Frush D.P.
        • Huda W.
        • Brent R.L.
        American Academy of Pediatrics section on R. Radiation risk to children from computed tomography.
        Pediatrics. 2007; 120: 677-682
        • Strauss K.J.
        • Goske M.J.
        • Kaste S.C.
        • Bulas D.
        • Frush D.P.
        • Butler P.
        • et al.
        Image gently: ten steps you can take to optimize image quality and lower CT dose for pediatric patients.
        AJR Am J Roentgenol. 2010; 194: 868-873
        • Kalra M.K.
        • Maher M.M.
        • Toth T.L.
        • Hamberg L.M.
        • Blake M.A.
        • Shepard J.A.
        • et al.
        Strategies for CT radiation dose optimization.
        Radiology. 2004; 230: 619-628
        • Kalender W.A.
        • Buchenau S.
        • Deak P.
        • Kellermeier M.
        • Langner O.
        • van Straten M.
        • et al.
        Technical approaches to the optimisation of CT.
        Phys Med. 2008; 24: 71-79
        • Kalra M.K.
        • Maher M.M.
        • Toth T.L.
        • Schmidt B.
        • Westerman B.L.
        • Morgan H.T.
        • et al.
        Techniques and applications of automatic tube current modulation for CT.
        Radiology. 2004; 233: 649-657
        • Gies M.
        • Kalender W.A.
        • Wolf H.
        • Suess C.
        Dose reduction in CT by anatomically adapted tube current modulation I. Simulation studies.
        Med Phys. 1999; 26: 2235-2247
        • Kalender W.A.
        • Wolf H.
        • Suess C.
        • Gies M.
        • Greess H.
        • Bautz W.A.
        Dose reduction in CT by on-line tube current control: principles and validation on phantoms and cadavers.
        Eur Radiol. 1999; 9: 323-328
        • Soderberg M.
        • Gunnarsson M.
        Automatic exposure control in computed tomography–an evaluation of systems from different manufacturers.
        Acta Radiol. 2010; 51: 625-634
        • Rampado O.
        • Marchisio F.
        • Izzo A.
        • Garelli E.
        • Bianchi C.C.
        • Gandini G.
        • et al.
        Effective dose and image quality evaluations of an automatic CT tube current modulation system with an anthropomorphic phantom.
        Eur J Radiol. 2009; 72: 181-187
        • Raman S.P.
        • Johnson P.T.
        • Deshmukh S.
        • Mahesh M.
        • Grant K.L.
        • Fishman E.K.
        CT dose reduction applications: available tools on the latest generation of CT scanners.
        J Am Coll Radiol JACR. 2013; 10: 37-41
      1. SIEMENS. SOMATOM Definition AS User Manual. In: AG S, editor, Germany 2012.

        • Papadakis A.E.
        • Perisinakis K.
        • Damilakis J.
        Automatic exposure control in pediatric and adult multidetector CT examinations: a phantom study on dose reduction and image quality.
        Med Phys. 2008; 35: 4567-4576
        • Papadakis A.E.
        • Perisinakis K.
        • Damilakis J.
        Automatic exposure control in CT: the effect of patient size, anatomical region and prescribed modulation strength on tube current and image quality.
        Eur Radiol. 2014; 24: 2520-2531
        • Papadakis A.E.
        • Perisinakis K.
        • Oikonomou I.
        • Damilakis J.
        Automatic exposure control in pediatric and adult computed tomography examinations: can we estimate organ and effective dose from mean MAS reduction?.
        Invest Radiol. 2011; 46: 654-662
        • Beister M.
        • Kolditz D.
        • Kalender W.A.
        Iterative reconstruction methods in X-ray CT.
        Phys Med. 2012; 28: 94-108
        • Greffier J.
        • Fernandez A.
        • Macri F.
        • Freitag C.
        • Metge L.
        • Beregi J.P.
        Which dose for what image? Iterative reconstruction for CT scan.
        Diagn Interventional Imaging. 2013; 94: 1117-1121
        • Mieville F.A.
        • Gudinchet F.
        • Brunelle F.
        • Bochud F.O.
        • Verdun F.R.
        Iterative reconstruction methods in two different MDCT scanners: physical metrics and 4-alternative forced-choice detectability experiments–a phantom approach.
        Phys Med. 2013; 29: 99-110
        • Greffier J.
        • Macri F.
        • Larbi A.
        • Fernandez A.
        • Khasanova E.
        • Pereira F.
        • et al.
        Dose reduction with iterative reconstruction: optimization of CT protocols in clinical practice.
        Diagn Interventional Imaging. 2015; 96: 477-486
        • Greffier J.
        • Macri F.
        • Larbi A.
        • Fernandez A.
        • Pereira F.
        • Mekkaoui C.
        • et al.
        Dose reduction with iterative reconstruction in multi-detector CT: what is the impact on deformation of circular structures in phantom study?.
        Diagn Interventional Imaging. 2016; 97: 187-196
        • Ott J.G.
        • Becce F.
        • Monnin P.
        • Schmidt S.
        • Bochud F.O.
        • Verdun F.R.
        Update on the non-prewhitening model observer in computed tomography for the assessment of the adaptive statistical and model-based iterative reconstruction algorithms.
        Phys Med Biol. 2014; 59: 4047-4064
        • Verdun F.R.
        • Racine D.
        • Ott J.G.
        • Tapiovaara M.J.
        • Toroi P.
        • Bochud F.O.
        Image quality in CT: from physical measurements to model observers.
        Physica medica: PM: an international journal devoted to the applications of physics to medicine and biology: official journal of the Italian Association of Biomedical Physics. 2015;
        Arrêté du 24 october 2011 relatif aux niveaux de référence diagnostiques en radiologie et en médecine nucléaire.
        in: MINISTÈRE DU TRAVAIL DLEEDLS Décrets, arrêtés, circulaires. 2012: 1-6
        • Brisse H.J.
        • Aubert B.
        CT exposure from pediatric MDCT: results from the 2007–2008 SFIPP/ISRN survey.
        J Radiol. 2009; 90: 207-215
        • Verdun F.R.
        • Gutierrez D.
        • Vader J.P.
        • Aroua A.
        • Alamo-Maestre L.T.
        • Bochud F.
        • et al.
        CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland.
        Eur Radiol. 2008; 18: 1980-1986
        • Buls N B.H.
        • Mommaert C.
        • Malchair F.
        • Clapuyt P.
        • Everarts P.
        CT paediatric doses in Belgium: a multi-centre study – results from a dosimetry audit in 2007–2009.
        Belgian Federal Agency of Nuclear Control (FANC), 2010
        • AAPM
        Size-specific dose estimates (SSDE) in pediatric and adult body CT examinations.
        AAPM Report No 204. 2011