title: Radiation dose and image noise evaluation in coronary computed tomography angiography (CCTA) using an iterative reconstruction algorithm.
abstract: BACKGROUND
  The purpose of this study was to evaluate radiation dose reduction in coronary computerised tomography angiography (CCTA), using a commercially available iterative reconstruction (IR) algorithm as well as the behaviour of the image noise.
  
  
  METHODS
  A total cohort of 47 patients underwent CCTA examination on a 64-slice multi-detector CT. They were divided into four groups according to the time when the examination was performed (before or after the installation of iDose) and the acquisition protocol followed (prospective or retrospective electrocardiography-ECG gated). The images acquired with reduced dose settings were reconstructed using two levels (L4 and L6) of the iDose4 algorithm. Image noise was measured in all cases.
  
  
  RESULTS
  In retrospective acquisition, images acquired with a 46% lower radiation dose and reconstructed with iDose4 L6 provided noise comparable to that in the full-dose filtered back-projection images. For the prospective acquisition mode, a slight decrease (26%) in radiation dose resulted in noise improvement in low-dose images reconstructed with iDose4 L4 (16% noise removal) and L6 (30% noise removal).
  
  
  CONCLUSIONS
  The fact that image quality is improved while radiation exposure is reduced indicates that there is room for a further reduction in exposure settings. Additionally, the combination of iDose4 with prospective acquisition is able to significantly reduce the radiation dose associated with CCTA at values of about 2 mSv and even lower.
authors.affiliation: Second Dept. of Radiology, Medical School, National and Kapodistrian University of Athens, Greece.
authors.forename: Sofia D
authors.initials: SD
authors.lastname: Kordolaimi
authors.forename: Stylianos
authors.initials: S
authors.lastname: Argentos
authors.forename: George
authors.initials: G
authors.lastname: Stathis
authors.forename: Antigoni
authors.initials: A
authors.lastname: Alexiou
authors.forename: Ioannis
authors.initials: I
authors.lastname: Pantos
authors.forename: Demosthenes G
authors.initials: DG
authors.lastname: Katritsis
authors.forename: Nikolaos L
authors.initials: NL
authors.lastname: Kelekis
authors.forename: Ioannis
authors.initials: I
authors.lastname: Seimenis
authors.forename: Efstathios P
authors.initials: EP
authors.lastname: Efstathopoulos
mesh_terms: D000368:Aged; D000465:Algorithms; D017023:Coronary Angiography / Q000379:methods*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods