title: Image quality and radiation dose of low dose coronary CT angiography in obese patients: sinogram affirmed iterative reconstruction versus filtered back projection.
abstract: OBJECTIVE
  To investigate the image quality and radiation dose of low radiation dose CT coronary angiography (CTCA) using sinogram affirmed iterative reconstruction (SAFIRE) compared with standard dose CTCA using filtered back-projection (FBP) in obese patients.
  
  
  METHODS
  Seventy-eight consecutive obese patients were randomized into two groups and scanned using a prospectively ECG-triggered step-and-shot (SAS) CTCA protocol on a dual-source CT scanner. Thirty-nine patients (protocol A) were examined using a routine radiation dose protocol at 120 kV and images were reconstructed with FBP (protocol A). Thirty-nine patients (protocol B) were examined using a low dose protocol at 100 kV and images were reconstructed with SAFIRE. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1=non-diagnostic, 4=excellent) and measured the objective parameters image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Radiation dose was calculated.
  
  
  RESULTS
  The coronary artery image quality scores, image noise, SNR and CNR were not significantly different between protocols A and B (all p>0.05), with image quality scores of 3.51±0.70 versus 3.55±0.47, respectively. The effective radiation dose was significantly lower in protocol B (4.41±0.83 mSv) than that in protocol A (8.83±1.74 mSv, p<0.01).
  
  
  CONCLUSIONS
  Compared with standard dose CTCA using FBP, low dose CTCA using SAFIRE can maintain diagnostic image quality with 50% reduction of radiation dose.
authors.affiliation: Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, 100029 Beijing, China. rui_wang1979@yahoo.cn
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: U Joseph
authors.initials: UJ
authors.lastname: Schoepf
authors.forename: Runze
authors.initials: R
authors.lastname: Wu
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Reddy
authors.forename: Chuanchen
authors.initials: C
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Yu
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhaoqi
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000465:Algorithms; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000150:complications* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; 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