title: Reduction of radiation dose estimates in cardiac 64-slice CT angiography in patients after coronary artery bypass graft surgery.
abstract: OBJECTIVE
  The objectives of this prospective investigation in patients after bypass graft surgery were (1) to estimate radiation dose for routine bypass graft computed tomography (CT) angiography, (2) to study the impact of anatomically adapted and ECG-controlled tube current modulation on radiation dose estimates, and (3) effects on qualitative and quantitative image quality parameters.
  
  
  METHODS
  Radiation dose was estimated for 194 consecutive patients undergoing 64-slice CT angiography (Somatom Sensation 64 Cardiac, Siemens Medical Solutions). The impact of anatomically adapted tube current modulation was studied in 2 consecutive patients groups. Furthermore, the impact of ECG-controlled tube current modulation, applied as indicated, was evaluated in both groups.
  
  
  RESULTS
  Mean radiation dose estimate for a 64-slice CT bypass graft study was 18.9 +/- 6.0 mSv (CTDIvol 42.3 +/- 12.9 mGy). The application of anatomically adapted tube current modulation had no effect on dose parameters (CTDIvol 43.3 +/- 13.2 vs. 40.1 +/- 12.1 mGy for those with versus those without anatomically adapted tube current modulation, P = 0.1). Additional implementation of ECG-controlled tube current modulation resulted in reduced dose parameters (CTDIvol of 32.9 +/- 2.6 vs. 58.9 +/- 3.9 mGy and radiation dose estimates: 14.7 +/- 1.9 mSv vs. 26.5 +/- 2.1 mSv for those with versus those without ECG pulsing, both P < 0.01). There was no deterioration in image quality with use of tube current modulation algorithms.
  
  
  CONCLUSIONS
  The radiation burden associated with 64-slice bypass graft CT angiographies is substantial. Anatomically adapted tube current modulation does not reduce radiation dose parameters, whereas ECG-controlled tube current modulation was associated with a 45% reduction in dose estimates. Application of both tube current modulation algorithms did not result in reduced image quality.
authors.affiliation: Institut für Radiologie und Nuklearmedizin, Deutsches Herzzentrum München, München, München, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Hermann
authors.forename: Stefan
authors.initials: S
authors.lastname: Martinoff
authors.forename: Tanja
authors.initials: T
authors.lastname: Meyer
authors.forename: Martin
authors.initials: M
authors.lastname: Hadamitzky
authors.forename: Chaohui
authors.initials: C
authors.lastname: Jiang
authors.forename: Eva
authors.initials: E
authors.lastname: Hendrich
authors.forename: Jörg
authors.initials: J
authors.lastname: Hausleiter
mesh_terms: D000368:Aged; D000465:Algorithms; D016009:Chi-Square Distribution; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D001026:Coronary Artery Bypass; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media