title: Dual-source CT in step-and-shoot mode: noninvasive coronary angiography with low radiation dose.
abstract: OBJECTIVE
  To prospectively investigate computed tomographic (CT) image quality parameters by using different protocols and to calculate radiation dose estimates for noninvasive coronary angiography performed with dual-source CT in the step-and-shoot (SAS) mode.
  
  
  METHODS
  This study was local ethics board approved; written informed consent was obtained from all patients. In the preliminary portion of the study, 40 patients underwent CT coronary angiography in the SAS mode: at 100 kV (protocol A) in 22 patients with a body mass index (BMI) of less than 25 kg/m(2) and at 120 kV (protocol B) in 18 patients with a BMI of 25-30 kg/m(2). Both protocols involved use of an attenuation-based tube current and 1 mL of contrast material per kilogram of body weight. The final portion of the study involved 50 additional patients: 21 patients with a BMI of 25-30 kg/cm(2) assigned to protocol B and 29 patients with a BMI of less than 25 kg/cm(2) assigned to protocol C, which was performed with 100 kV, an attenuation-based tube current, and a reduced contrast material dose of 0.8 mL/kg. Image quality was independently assessed. Attenuation in the aorta and coronary arteries and image noise were measured. Radiation dose was estimated.
  
  
  RESULTS
  Mean image noise was similar with protocols A and B. Mean attenuation in the aorta and coronary arteries with protocol A (444 HU) was significantly (P < .001) higher than that with protocol B (358 HU). The reduced contrast material dose in protocol C yielded attenuation similar to that with protocol B. Diagnostic image quality was achieved with all protocols in 1237 (97.9%) of 1264 coronary segments. No significant differences in image quality between the 100- and 120-kV protocols were found. Mean heart rate had a significant effect on motion artifacts (area under receiver operating characteristic curve [AUC] = 0.818; 95% confidence interval [CI]: 0.723, 0.892; P < .001), whereas heart rate variability had a significant effect on stair-step artifacts (AUC = 0.79; 95% CI: 0.687, 0.865; P < .001). The mean estimated effective dose was 1.2 mSv +/- 0.2 for protocols A and C and 2.6 mSv +/- 0.5 for protocol B.
  
  
  CONCLUSIONS
  Dual-source SAS-mode CT coronary angiography yielded diagnostic image quality for 97.9% of coronary segments at a low radiation dose.
authors.affiliation: Institute of Diagnostic Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Leschka
authors.forename: Hans
authors.initials: H
authors.lastname: Scheffel
authors.forename: Tobias
authors.initials: T
authors.lastname: Krauss
authors.forename: Lotus
authors.initials: L
authors.lastname: Desbiolles
authors.forename: André
authors.initials: A
authors.lastname: Plass
authors.forename: Michele
authors.initials: M
authors.lastname: Genoni
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Flohr
authors.forename: Simon
authors.initials: S
authors.lastname: Wildermuth
authors.forename: Borut
authors.initials: B
authors.lastname: Marincek
authors.forename: Hatem
authors.initials: H
authors.lastname: Alkadhi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017023:Coronary Angiography / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods*