title: Dose reduction in multi-slice CT of the heart by use of ECG-controlled tube current modulation ("ECG pulsing"): phantom measurements.
abstract: OBJECTIVE
  To evaluate the effect of ECG-controlled tube current modulation on radiation exposure in retrospectively-ECG-gated multislice CT (MSCT) of the heart.
  
  
  METHODS
  Three different cardiac MSCT protocols with different slice collimation (4 x 1, and 4 x 2.5mm), and a pitch-factor of 1.5 and 1.8 were investigated at a multi-slice CT scanner Somatom Volume Zoom, Siemens. An anthropomorphic Alderson-Rando phantom was equipped with LiF-thermoluminescence dosimeters at several organ sites, and effective doses were calculated using ICRP-weighting factors. Scan protocols were performed with ECG-controlled tube current modulation ("ECG pulsing") at two different heart rates (60 and 80 bpm). These data were compared to previous data from MSCT of the heart without use of "ECG pulsing".
  
  
  RESULTS
  Radiation exposure with (60 bpm) and without tube current modulation using a 2.5 mm collimation was 1.8 mSv and 2.9 mSv for females, and 1.5 mSv and 2.4 mSv for males, respectively. For protocols using a 1 mm collimation with a pitch-factor of 1.5 (1.8), radiation exposure with and without tube current modulation was 5.6 (6.3) mSv and 9.5 (11.2) mSv for females, and 4.6 (5.2) mSv and 7.7 (9.2) mSv for males, respectively. At higher heart rates (80 bpm) radiation exposure is increased from 1.5 - 1.8 mSv to 1.8 - 2.1 mSv, using the 2.5 mm collimation, and from 4.6 - 5.6 mSv to 5.9 - 7.2 mSv, for protocols using 1 mm collimation.
  
  
  CONCLUSIONS
  The ECG-controlled tube current modulation allows a dose reduction of 37 % to 44 % when retrospectively ECG-gated MSCT of the heart is performed. The tube current - as a function over time - and therefore the radiation exposure is dependent on the heart rate.
authors.affiliation: Institute of Diagnostic Radiology, Universitätsklinikum Düsseldorf (UKD), Heinrich-Heine-University Düsseldorf, Germany. polll@uni-duesseldorf.de
authors.forename: L W
authors.initials: LW
authors.lastname: Poll
authors.forename: M
authors.initials: M
authors.lastname: Cohnen
authors.forename: S
authors.initials: S
authors.lastname: Brachten
authors.forename: K
authors.initials: K
authors.lastname: Ewen
authors.forename: U
authors.initials: U
authors.lastname: Mödder
mesh_terms: D017023:Coronary Angiography; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012189:Retrospective Studies; D012737:Sex Factors; D013819:Thermoluminescent Dosimetry; D014057:Tomography, X-Ray Computed / Q000379:methods*