title: Potential dose reduction of optimal ECG-controlled tube current modulation for 256-slice CT coronary angiography.
abstract: OBJECTIVE
  The purpose of this study was to design an optimized heart rate (HR)-dependent electrocardiogram (ECG) pulsing protocol for computed tomography coronary angiography (CTCA) on a 256-slice CT scanner and to assess its potential dose reduction retrospectively, based on the retrospective ECG gating data without dose modulation.
  
  
  METHODS
  A total of 137 patients were enrolled to perform CTCA with a 256-slice scanner. Two independent radiologists graded image quality of coronary artery segments (1 = excellent, no motion artifacts; 4 = poor, severe motion artifacts) to define optimal reconstruction window in end-systolic phase, mid-diastolic phase, and the combination of both cardiac phases. According to statistical analysis for HR against image quality, four HR-depended ECG-pulsing protocols were proposed. We also demonstrated the potential dose reduction of the proposed technique.
  
  
  RESULTS
  For patients with HR <59 beats/min (group 1), 60-72 beats/min (group 2), 73-84 beats/min (group 3), and >85 beats/min (group 4), the optimal reconstruction windows were at 74.1-81.3%, 73.4-82.2%, 38.3-82.3%, and 37.2-61.6% of R-R interval, respectively. The ECG-pulsing protocols with minimal radiation dose (ie, no tube current outside the pulsing window) can reduce the effective dose of CTCA by 79.5%, 75.7%, 38.3%, and 57.4% for HR groups 1 to 4, respectively. The corresponding results for reducing tube current by 80% outside the pulsing window were 63.7%, 56.6%, 32.0%, and 46.0%.
  
  
  CONCLUSIONS
  Through the optimization of ECG-pulsed tube-current modulation, radiation exposure can be greatly reduced, especially in patients with HR <72 beats/min or >85 beats/min.
authors.affiliation: Department of Radiological Technology, Tzu Chi College of Technology, Hualien, Taiwan.
authors.forename: Ching-Ching
authors.initials: CC
authors.lastname: Yang
authors.forename: Greta S P
authors.initials: GS
authors.lastname: Mok
authors.forename: Wei-Yip
authors.initials: WY
authors.lastname: Law
authors.forename: Shih-Ming
authors.initials: SM
authors.lastname: Hsu
authors.forename: Tung-Hsin
authors.initials: TH
authors.lastname: Wu
authors.forename: Liang-Kuang
authors.initials: LK
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009038:Motion; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media