title: Improved non-calcified plaque delineation on coronary CT angiography by sonogram-affirmed iterative reconstruction with different filter strength and relationship with BMI.
abstract: OBJECTIVE
  To prospectively compare non-calcified plaque delineation and image quality of coronary computed tomography angiography (CCTA) obtained with sinogram-affirmed iterative reconstruction (IR) with different filter strengths and filtered back projection (FBP).
  
  
  METHODS
  A total of 57 patients [28.1% females; body mass index (BMI) 29.2±6.5 kg/m(2)] were investigated. CCTA was performed using 128-slice dual-source CT. Images were reconstructed with standard FBP and sinogram-affirmed IR using different filter strength (IR-2, IR-3, IR-4) (SAFIRE, Siemens, Germany). Image quality of CCTA and a non-calcified plaque outer border delineation score were evaluated by using a 5-scale score: from 1= poor to 5= excellent. Image noise, contrast-to-noise ratio (CNR) of aortic root, left main (LM) and right coronary artery, and the non-calcified plaque delineation were quantified and compared among the 4 image reconstructions, and were compared between different BMI groups (BMI <28 and ≥28). Statistical analyses included one-way analysis of variance (ANOVA), least significant difference (LSD) and Kruskal-Wallis test.
  
  
  RESULTS
  There were 71.9% patients in FBP, 96.5% in IR-2, 96.5% in IR-3 and 98.2% in IR-4 who had overall CCTA image quality ≥3, and there were statistical differences in CCTA exam image quality score among those groups, respectively (P<0.001). Sixty-one non-calcified plaques were detected by IR-2 to IR-4, out of those 11 (18%) were missed by FBP. Plaque delineation score increased constantly from FBP (2.7±0.4) to IR-2 (3.2±0.3), to IR-3 (3.5±0.3) up to IR-4 (4.0±0.4), while CNRs of the non-calcifying plaque increased and image noise decreased, respectively. Similarly, CNR of aortic root, LM and right coronary artery improved and image noise declined from FBP to IR-2, IR-3 and IR-4. There were no significant differences of image quality and plaque delineation score between low and high BMI groups within same reconstruction (all P>0.05). Significant differences in image quality and plaque delineation scores among different image reconstructions both in low and high BMI groups (all P<0.001) were found. I4f revealed the highest image quality and plaque delineation score.
  
  
  CONCLUSIONS
  IR offers improved image quality and non-calcified plaque delineation as compared with FBP, especially if BMI is increasing. Importantly, 18% of non-calcified plaques were missed with FBP. IR-4 shows the best image quality score and plaque delineation score among the different IR-filter strength.
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Fabian
authors.initials: F
authors.lastname: Plank
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Moritz
authors.initials: M
authors.lastname: Kummann
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Burghard
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Andrea
authors.initials: A
authors.lastname: Klauser
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dichtl
authors.affiliation: 1 Beijing Anzhen Hospital, Capital Medical University, Department of Radiology, Chaoyang District, Beijing 100029, China ; 2 Innsbruck Medical University, Department of Radiology, 3 Innsbruck Medical University, Department of Cardiology, Innrain 52, Christoph-Probst-Platz, 6020 Innsbruck, Tyrol, Austria.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Feuchtner
keywords: Non-calcified plaque; coronary computed tomography angiography (CCTA); sinogram-affirmed iterative reconstruction (sinogram-affirmed IR)