title: Radiation dose in 320-slice multidetector cardiac CT: a single center experience of evolving dose minimization.
abstract: BACKGROUND
  Minimization of radiation exposure remains an important subject that occurs in parallel with advances in scanner technology.
  
  
  OBJECTIVE
  We report our experience of evolving radiation dose and its determinants after the introduction of 320-multidetector row cardiac CT within a single tertiary cardiology referral service.
  
  
  METHODS
  Four cohorts of consecutive patients (total 525 scans), who underwent cardiac CT at defined time points as early as 2008, are described. These include a cohort just after scanner installation, after 2 upgrades of the operating system, and after introduction of an adaptive iterative image reconstruction algorithm. The proportions of nondiagnostic coronary artery segments and studies with nondiagnostic segments were compared between cohorts.
  
  
  RESULTS
  Significant reductions were observed in median radiation doses in all cohorts compared with the initial cohort (P < .001). Median dose-length product fell from 944 mGy · cm (interquartile range [IQR], 567.3-1426.5 mGy · cm) to 156 mGy · cm (IQR, 99.2-265.0 mGy · cm). Although the proportion of prospectively triggered scans has increased, reductions in radiation dose have occurred independently of distribution of scan formats. In multiple regression that combined all groups, determinants of dose-length product were tube output, the number of cardiac cycles scanned, tube voltage, scan length, scan format, body mass index, phase width, and heart rate (adjusted R(2) = 0.85, P < .001). The proportion of nondiagnostic coronary artery segments was slightly increased in group 4 (2.9%; P < .01).
  
  
  CONCLUSIONS
  While maintaining diagnostic quality in 320-multidetector row cardiac CT, the radiation dose has decreased substantially because of a combination of dose-reduction protocols and technical improvements. Continued minimization of radiation dose will increase the potential for cardiac CT to expand as a cardiac imaging modality.
authors.affiliation: Monash Cardiovascular Research Center, MonashHEART, Monash Medical Center, 246 Clayton Road, Clayton 3168, Australia.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Tung
authors.forename: James D
authors.initials: JD
authors.lastname: Cameron
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Casan
authors.forename: Marcus
authors.initials: M
authors.lastname: Crossett
authors.forename: John M
authors.initials: JM
authors.lastname: Troupis
authors.forename: Ian T
authors.initials: IT
authors.lastname: Meredith
authors.forename: Sujith K
authors.initials: SK
authors.lastname: Seneviratne
mesh_terms: D000465:Algorithms; D016477:Artifacts; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging*; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012044:Regression Analysis
keywords: Adaptive iterative dose reconstruction; Cardiac CT; Coronary CT angiography; Multidetector row CT; Radiation dose