title: Effect of iDose4 iterative reconstruction algorithm on image quality and radiation exposure in prospective and retrospective electrocardiographically gated coronary computed tomographic angiography.
abstract: OBJECTIVE
  The aims of this study were to compare a commercially available reconstruction algorithm (iDose4) with filtered back projection (FBP) in terms of image quality (IQ) for both retrospective electrocardiographically gated and prospective electrocardiographically triggered cardiac computed tomographic angiography (CCTA) protocols and to evaluate the achievable radiation dose reduction.
  
  
  METHODS
  A total cohort of 58 patients underwent either prospective CTCA or retrospective CTCA with full or reduced tube current-time product (in milliampere-second) protocol on a 64-slice multidetector computed tomographic scanner. All images were reconstructed with FBP, whereas the reduced milliampere-second images were also reconstructed using 2 levels (levels 4 and 6) of iDose4. Subjective and objective IQ was evaluated.
  
  
  RESULTS
  Dose reductions of 43% in the retrospective CCTA protocol and 27% in the prospective CCTA protocol were achieved without compromising IQ. In the prospective CCTA protocol, the reduced-dose images were highly scored; thus, additional reduction of exposure settings is feasible. In the retrospective acquisition, dose reduction has led to similar IQ scores between the reduced-dose iDose4 images and the full-dose FBP images. Considering different reconstructions (FBP, iDose-L4 and -L6) of the same acquisition data, increase in iDose4 level resulted in less noisy images. A slight improvement was also noticed in all IQ indices; however, this improvement was not statistically significant for both acquisition protocols.
  
  
  CONCLUSIONS
  This study demonstrated that the application of iDose at CCTA facilitates significant radiation dose reduction by maintaining diagnostic quality. The combination of iDose4 with prospective acquisition is able to significantly reduce effective dose associated with CTCA at values of approximately 2 mSv and even lower.
authors.affiliation: From the *Second Department of Radiology, School of Medicine, University of Athens; and †Department of Cardiology, Athens Euroclinic, Athens, Greece.
authors.forename: Sofia D
authors.initials: SD
authors.lastname: Kordolaimi
authors.forename: Stylianos
authors.initials: S
authors.lastname: Argentos
authors.forename: Maria
authors.initials: M
authors.lastname: Mademli
authors.forename: George
authors.initials: G
authors.lastname: Stathis
authors.forename: Ioannis
authors.initials: I
authors.lastname: Pantos
authors.forename: Agapi
authors.initials: A
authors.lastname: Ploussi
authors.forename: Demosthenes
authors.initials: D
authors.lastname: Katritsis
authors.forename: Efstathios P
authors.initials: EP
authors.lastname: Efstathopoulos
mesh_terms: D000465:Algorithms; D017023:Coronary Angiography / Q000379:methods* / Q000592:standards*; D004562:Electrocardiography / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011446:Prospective Studies; D011829:Radiation Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed