title: Radiation dose reduction at coronary artery calcium scoring by using a low tube current technique and hybrid iterative reconstruction.
abstract: OBJECTIVE
  The aim of this study was to compare the accuracy of coronary artery calcium scoring (CACS) on cardiac computed tomographic images using hybrid iterative reconstruction (hIR) and a low tube current as well as on images acquired with a filtered back projection (FBP) algorithm and a normal tube current.
  
  
  METHODS
  Patients (N = 77) with suspected coronary artery disease were subjected to 2 CACS evaluations based on their Agatston, volume, and mass scores. One CACS evaluation was performed on images obtained with a 364-mA tube current and reconstructed with FBP; the other was performed on images obtained with a 73-mA tube current and reconstructed with hIR at iDose4. All scans were performed with the prospective electrocardiogram-triggered method using a 256-slice computed tomographic scanner (Brilliance iCT; Philips). We assessed agreement between calcium scores obtained with FBP and with IR using the percentage difference and Bland-Altman analysis.
  
  
  RESULTS
  The effective radiation doses for CACS at 80 mA s with FBP and at 16 mA s with IR were 1.20 and 0.24 mSv, respectively (k = 0.014). The mean Agatston, volume, and mass scores at 80 mA s with FBP as well as at 16 mA s with IR were 390.7, 146.5, and 63.2 as well as 377.7, 142.5, and 62.2, respectively. The percentage difference between FBP and hIR for the Agatston, volume, and mass score was 20.7%, 20.7%, and 27.1%, respectively. Bland-Altman analysis showed that there was no systemic bias.
  
  
  CONCLUSIONS
  The radiation dose for CACS can be reduced at a low tube current and hIR without affecting the calcium score.
authors.affiliation: From the *Department of Diagnostic Radiology, Kure Medical Center, Kure; †Department of Diagnostic Radiology, Hiroshima City Hospital; and ‡Department of Diagnostic Radiology, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Matsuura
authors.forename: Masaki
authors.initials: M
authors.lastname: Urashima
authors.forename: Wataru
authors.initials: W
authors.lastname: Fukumoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sunamori
authors.forename: Fuminari
authors.initials: F
authors.lastname: Tatsugami
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Toyota
authors.forename: Kazuo
authors.initials: K
authors.lastname: Awai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002114:Calcinosis / Q000000981:diagnostic imaging*; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*