title: Reduction of radiation exposure and improvement of image quality with BMI-adapted prospective cardiac computed tomography and iterative reconstruction.
abstract: OBJECTIVE
  To assess the impact of body mass index (BMI)-adapted protocols and iterative reconstruction algorithms (iDose) on patient radiation exposure and image quality in patients undergoing prospective ECG-triggered 256-slice coronary computed tomography angiography (CCTA).
  
  
  METHODS
  Image quality and radiation exposure were systematically analyzed in 100 patients. 60 Patients underwent prospective ECG-triggered CCTA using a non-tailored protocol and served as a 'control' group (Group 1: 120 kV, 200 mAs). 40 Consecutive patients with suspected coronary artery disease (CAD) underwent prospective CCTA, using BMI-adapted tube voltage and standard (Group 2: 100/120 kV, 100-200 mAs) versus reduced tube current (Group 3: 100/120 kV, 75-150 mAs). Iterative reconstructions were provided with different iDose levels and were compared to filtered back projection (FBP) reconstructions. Image quality was assessed in consensus of 2 experienced observers and using a 5-grade scale (1=best to 5=worse), and signal- and contrast-to-noise ratios (SNR and CNR) were quantified.
  
  
  RESULTS
  CCTA was performed without adverse events in all patients (n=100, heart rate of 47-87 bpm and BMI of 19-38 kg/m2). Patients examined using the non-tailored protocol in Group 1 had the highest radiation exposure (3.2±0.4 mSv), followed by Group 2 (1.7±0.7 mSv) and Group 3 (1.2±0.6 mSv) (radiation savings of 47% and 63%, respectively, p<0.001). Iterative reconstructions provided increased SNR and CNR, particularly when higher iDose level 5 was applied with Multi-Frequency reconstruction (iDose5 MFR) (14.1±4.6 versus 21.2±7.3 for SNR and 12.0±4.2 versus 18.1±6.6 for CNR, for FBP versus iDose5 MFR, respectively, p<0.001). The combination of BMI adaptation with iterative reconstruction reduced radiation exposure and simultaneously improved image quality (subjective image quality of 1.4±0.4 versus 1.9±0.5 for Group 2 reconstructed using iDose5 MFR versus Group 1 reconstructed using FBP, p<0.05).
  
  
  CONCLUSIONS
  Prospective ECG-triggered 256-slice CCTA allows for visualization of the coronary artery tree with high image quality within a wide range of heart rates and BMIs. The combination of BMI-adapted protocols with iterative reconstruction algorithms can reduce radiation exposure for the patients and simultaneously improve image quality.
authors.affiliation: University of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg, Germany. waldemar.hosch@med.uni-heidelberg.de
authors.forename: Waldemar
authors.initials: W
authors.lastname: Hosch
authors.forename: Wolfram
authors.initials: W
authors.lastname: Stiller
authors.forename: Dirk
authors.initials: D
authors.lastname: Mueller
authors.forename: Gitsios
authors.initials: G
authors.lastname: Gitsioudis
authors.forename: Johanna
authors.initials: J
authors.lastname: Welzel
authors.forename: Monika
authors.initials: M
authors.lastname: Dadrich
authors.forename: Sebastian J
authors.initials: SJ
authors.lastname: Buss
authors.forename: Evangelos
authors.initials: E
authors.lastname: Giannitsis
authors.forename: Hans U
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Katus
authors.forename: Grigorios
authors.initials: G
authors.lastname: Korosoglou
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D015992:Body Mass Index; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*