- •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.
Abbreviations: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)
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Published online: April 04, 2016
Accepted: March 16, 2016
Received in revised form: February 23, 2016
Received: December 9, 2015
© 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.