title: Image quality in a low radiation exposure protocol for retrospectively ECG-gated coronary CT angiography.
abstract: OBJECTIVE
  The purpose of our study was to systematically compare the image quality of dual-source CT coronary angiography using 100 kV instead of 120 kV.
  
  
  METHODS
  One hundred patients with a body weight </= 85 kg were included. A dual-source CT scanner was used (330-milliseconds rotation, 0.6-mm collimation, 56 +/- 7 mL of IV contrast agent at 5 mL/s). Each patient was randomized either to scanning protocol group 1 (120 kV and 330 mAs) or protocol group 2 (100 kV and 330 mAs). ECG pulsing was used for all patients. Data sets were assessed by two independent observers for image quality, signal-to-noise ratio, and contrast-to-noise-ratio. Effective dose was determined based on dose-length product.
  
  
  RESULTS
  There were no significant differences in body weight or heart rate between the two groups (70 +/- 10 kg and 57 +/- 8 bpm [beats per minute] vs 70 +/- 9 kg and 59 +/- 8 bpm). Use of 100 kV led to significant reduction of radiation exposure (group 1: 12.7 +/- 1.7 mSv; volume CT dose index [CTDI(vol)], 47.8 +/- 6.1 mGy and group 2: 7.8 +/- 2.0 mSv; CTDI(vol), 28.6 +/- 6.3 mGy; p < 0.001). Interobserver agreement in assessing image quality (kappa = 0.71) was close. Mean patient-based image quality scores were not significantly different (group 1, 2.7 +/- 0.5 and group 2, 2.6 +/- 0.4; p = 0.75). Also, vessel-based scores showed no significant differences. Beyond the level of significance, group 1 and group 2 showed one and two nonassessable patients and two and three nonassessable vessels, respectively. Mean intraluminal attenuation, contrast enhancement, and image noise were significantly higher for 100 kV, whereas signal-to-noise and contrast-to-noise-ratios were not different between the two scanning protocols.
  
  
  CONCLUSIONS
  The use of lower tube voltage leads to significant reduction in radiation exposure in noninvasive coronary CT angiography. Image quality in nonobese patients is not negatively influenced.
authors.affiliation: Department of Internal Medicine 2 (Cardiology), University of Erlangen, Ulmenweg 18, D-91054 Erlangen, Germany. tobias.pflederer@uk-erlangen.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Pflederer
authors.forename: Larissa
authors.initials: L
authors.lastname: Rudofsky
authors.forename: Dieter
authors.initials: D
authors.lastname: Ropers
authors.forename: Sven
authors.initials: S
authors.lastname: Bachmann
authors.forename: Mohamed
authors.initials: M
authors.lastname: Marwan
authors.forename: Werner G
authors.initials: WG
authors.lastname: Daniel
authors.forename: Stephan
authors.initials: S
authors.lastname: Achenbach
mesh_terms: D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods* / Q000592:standards; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007472:Iohexol / Q000031:analogs & derivatives; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000592:standards
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide