title: The impact of acquisition angle differences on three-dimensional quantitative coronary angiography.
abstract: BACKGROUND
  Three-dimensional (3D) quantitative coronary angiography (QCA) requires two angiographic views to restore vessel dimensions. This study investigated the impact of acquisition angle differences (AADs) of the two angiographic views on the assessed dimensions by 3D QCA.
  
  
  METHODS
  X-ray angiograms of an assembled brass phantom with different types of straight lesions were recorded at multiple angiographic projections. The projections were randomly matched as pairs and 3D QCA was performed in those pairs with AAD larger than 25°. The lesion length and diameter stenosis in three different lesions, a circular concentric severe lesion (A), a circular concentric moderate lesion (B), and a circular eccentric moderate lesion (C), were measured by 3D QCA. The acquisition protocol was repeated for a silicone bifurcation phantom, and the bifurcation angles and bifurcation core volume were measured by 3D QCA. The measurements were compared with the true dimensions if applicable and their correlation with AAD was studied.
  
  
  RESULTS
  50 matched pairs of angiographic views were analyzed for the brass phantom. The average value of AAD was 48.0 ± 14.1°. The percent diameter stenosis was slightly overestimated by 3D QCA for all lesions: A (error 1.2 ± 0.9%, P < 0.001); B (error 0.6 ± 0.5%, P < 0.001); C (error 1.1 ± 0.6%, P < 0.001). The correlation of the measurements with AAD was only significant for lesion A (R(2) = 0.151, P = 0.005). The lesion length was slightly overestimated by 3D QCA for lesion A (error 0.06 ± 0.18 mm, P = 0.026), but well assessed for lesion B (error -0.00 ± 0.16 mm, P = 0.950) and lesion C (error -0.01 ± 0.18 mm, P = 0.585). The correlation of the measurements with AAD was not significant for any lesion. Forty matched pairs of angiographic views were analyzed for the bifurcation phantom. The average value of AAD was 49.1 ± 15.4°. 3D QCA slightly overestimated the proximal angle (error 0.4 ± 1.1°, P = 0.046) and the distal angle (error 1.5 ± 1.3°, P < 0.001). The correlation with AAD was only significant for the distal angle (R(2) = 0.256, P = 0.001). The correlation of bifurcation core volume measurements with AAD was not significant (P = 0.750). Of the two aforementioned measurements with significant correlation with AAD, the errors tended to increase as AAD became larger.
  
  
  CONCLUSIONS
  3D QCA can be used to reliably assess vessel dimensions and bifurcation angles. Increasing the AAD of the two angiographic views does not increase accuracy and precision of 3D QCA for circular lesions or bifurcation dimensions.
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands. s.t.tu@lumc.nl
authors.forename: Shengxian
authors.initials: S
authors.lastname: Tu
authors.forename: Niels R
authors.initials: NR
authors.lastname: Holm
authors.forename: Gerhard
authors.initials: G
authors.lastname: Koning
authors.forename: Michael
authors.initials: M
authors.lastname: Maeng
authors.forename: Johan H C
authors.initials: JH
authors.lastname: Reiber
mesh_terms: D016477:Artifacts; D003300:Copper; D017023:Coronary Angiography / Q000295:instrumentation / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D015588:Observer Variation; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012828:Silicones; D015032:Zinc
chemical_list: D012828:Silicones; C048399:brass; D003300:Copper; D015032:Zinc