title: A Monte Carlo simulation for the estimation of patient dose in rest and stress cardiac computed tomography with a 320-detector row CT scanner.
abstract: OBJECTIVE
  To estimate organ dose and effective dose for patients for cardiac CT as applied in an international multicenter study (CORE320) with a 320-Detector row CT scanner using Monte Carlo (MC) simulations and voxelized phantoms. The effect of positioning of the arms, off-centering the patient and heart rate on patient dose was analyzed.
  
  
  METHODS
  A MC code was tailored to simulate the geometry and characteristics of the CT scanner. The phantoms representing the adult reference male and female were implemented according to ICRP 110. Effective dose and organ doses were obtained for CT acquisition protocols for calcium scoring, coronary angiography and myocardial perfusion.
  
  
  RESULTS
  For low heart rate, the normalized effective dose (E) for cardiac CT was higher for female (5.6 mSv/100 mAs) compared to male (2.2 mSv/100 mAs) due to the contribution of female breast tissue. Averaged E for female and male was 11.3 mSv for the comprehensive cardiac protocol consisting of calcium scoring (1.9 mSv); coronary angiography including rest cardiac perfusion (5.1 mSv) and stress cardiac perfusion (4.3 mSv). These values almost doubled at higher heart rates (20.1 mSv). Excluding the arms increased effective dose by 6-8%, centering the patient showed no significant effect. The k-factor (0.028 mSv/mGy.cm) derived from this study leads to effective doses up to 2-3 times higher than the values obtained using now outdated methodologies.
  
  
  CONCLUSIONS
  MC modeling of cardiac CT examinations on realistic voxelized phantoms allowed us to assess patient doses accurately and we derived k-factors that are well above those published previously.
authors.affiliation: Radiology Department, Leiden University Medical Center, Albinusdreef 2, Leiden 2333 ZA, Netherlands. Electronic address: J.Geleijns@lumc.nl.
authors.forename: Jacob
authors.initials: J
authors.lastname: Geleijns
authors.affiliation: Radiology Department, Leiden University Medical Center, Albinusdreef 2, Leiden 2333 ZA, Netherlands.
authors.forename: Raoul M S
authors.initials: RMS
authors.lastname: Joemai
authors.affiliation: Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili, Sant Llorenç 21, Reus 43201, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Cros
authors.affiliation: Radiology Department, Leiden University Medical Center, Albinusdreef 2, Leiden 2333 ZA, Netherlands.
authors.forename: Irene
authors.initials: I
authors.lastname: Hernandez-Giron
authors.affiliation: Radiology Department, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Calzado
authors.affiliation: Charité Centrum für diagnostische und interventionelle Radiologie und Nuklearmedizin Institut für Radiologie CCM, Charitéplatz 1, Berlin 10117, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Dewey
authors.affiliation: Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili, Sant Llorenç 21, Reus 43201, Spain.
authors.forename: Marçal
authors.initials: M
authors.lastname: Salvado
mesh_terms: D001132:Arm; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009010:Monte Carlo Method; D056888:Patient Positioning; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012146:Rest; D013312:Stress, Physiological; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: CT dosimetry; Effective dose to the patient; ICRP voxel phantoms; Monte Carlo simulation; Rest and stress cardiac computed tomography