In vivo assessment of bifurcation optimal viewing angles and bifurcation angles by threedimensional (3D) quantitative coronary angiography.  
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PMID: 22169957 Owner: NLM Status: MEDLINE 
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Evaluation and stenting of coronary bifurcation lesions may benefit from optimal angiographic views. The anatomydefined bifurcation optimal viewing angle (ABOVA) is characterized by having an orthogonal view of the bifurcation, such that overlap and foreshortening at the ostium are minimized. However, due to the mechanical constraints of the Xray systems, certain deep angles cannot be reached by the Carm. Therefore, second best or, socalled obtainable bifurcation optimal viewing angle (OBOVA) has to be used as an alternative. This study assessed the distributions of ABOVA and OBOVA using 3D quantitative coronary angiography in a typical patient population. In addition, the bifurcation angles in four main coronary bifurcations were assessed and compared. Patients with obstructive coronary bifurcation disease were included in this multicenter registry. A novel and validated 3D QCA software package was applied to reconstruct the bifurcations and to calculate the bifurcation angles in 3D. A list of optimal viewing angle candidates including ABOVA was also automatically proposed by the software. In a next step, the operator selected the best viewing angle as OBOVA, while applying a novel overlap prediction approach to assure no overlap between the target bifurcation and other major coronary arteries. A total of 194 bifurcations from 181 patients were assessed. The ABOVA could not be reached in 56.7% of the cases; being 40 (81.6%), 40 (78.4%), 9 (17.6%), and 21 (48.8%) cases for LM/LAD/LCx, LAD/Diagonal, LCx/OM, and PDA/PLA, respectively. Both ABOVA and OBOVA distributed sparsely with large ranges of variance: LM/LAD/LCx, 5 ± 33 RAO, 47 ± 35 Caudal versus 4 ± 39 LAO, 35 ± 16 Caudal; LAD/Diagonal, 4 ± 38 RAO, 50 ± 14 Cranial versus 14 ± 28 LAO, 33 ± 5 Cranial; LCx/OM, 21 ± 32 LAO, 27 ± 17 Caudal versus 18 ± 31 LAO, 25 ± 13 Caudal; PDA/PLA, 34 ± 21 LAO, 36 ± 21 Cranial versus 28 ± 25 LAO, 29 ± 15 Cranial. LM/LAD/LCx had the smallest proximal bifurcation angle (128° ± 24°) and the largest distal bifurcation angle (80° ± 21°), as compared with LAD/Diagonal (151° ± 13º and 48° ± 16º), LCx/OM (146° ± 18º and 57° ± 16°), and PDA/PLA (145° ± 19° and 59° ± 17°). In conclusion, large variabilities in optimal viewing angles existed for all main coronary bifurcations. The anatomydefined bifurcation optimal viewing angle could not be reached in vivo in roughly half of the cases due to the mechanical constraints of the current Xray systems. Obtainable bifurcation optimal viewing angle should be provided as an alternative or second best. The bifurcation angles in the left main bifurcation demonstrated the largest variabilities. 
Authors:

Shengxian Tu; Jing Jing; Niels R Holm; Kevin Onsea; Tao Zhang; Tom Adriaenssens; Christophe Dubois; Walter Desmet; Leif Thuesen; Yundai Chen; Johan H C Reiber 
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Publication Detail:

Type: Journal Article; Multicenter Study Date: 20111215 
Journal Detail:

Title: The international journal of cardiovascular imaging Volume: 28 ISSN: 18758312 ISO Abbreviation: Int J Cardiovasc Imaging Publication Date: 2012 Oct 
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Created Date: 20121017 Completed Date: 20130402 Revised Date: 20130627 
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Nlm Unique ID: 100969716 Medline TA: Int J Cardiovasc Imaging Country: United States 
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Languages: eng Pagination: 161725 Citation Subset: IM 
Affiliation:

Division of Image Processing, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, The Netherlands. S.T.Tu@lumc.nl 
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Adult Aged Aged, 80 and over Belgium China Coronary Angiography / methods* Coronary Artery Disease / radiography* Denmark Female Humans Imaging, ThreeDimensional* Male Middle Aged Predictive Value of Tests Radiographic Image Interpretation, ComputerAssisted* Retrospective Studies Software Tomography, XRay Computed* 
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Journal Information Journal ID (nlmta): Int J Cardiovasc Imaging Journal ID (isoabbrev): Int J Cardiovasc Imaging ISSN: 15695794 ISSN: 18758312 Publisher: Springer Netherlands, Dordrecht 
Article Information Download PDF © The Author(s) 2011 Received Day: 24 Month: 8 Year: 2011 Accepted Day: 2 Month: 12 Year: 2011 Electronic publication date: Day: 15 Month: 12 Year: 2011 pmcrelease publication date: Day: 15 Month: 12 Year: 2011 Print publication date: Month: 10 Year: 2012 Volume: 28 Issue: 7 First Page: 1617 Last Page: 1625 ID: 3473185 PubMed Id: 22169957 Publisher Id: 9996 DOI: 10.1007/s105540119996x 
In vivo assessment of bifurcation optimal viewing angles and bifurcation angles by threedimensional (3D) quantitative coronary angiography  
Shengxian Tu1 
Address: S.T.Tu@lumc.nl 
Jing Jing2  
Niels R. Holm3  
Kevin Onsea4  
Tao Zhang2  
Tom Adriaenssens4  
Christophe Dubois4  
Walter Desmet4  
Leif Thuesen3  
Yundai Chen2 
Address: cyundai@medmail.com.cn 
Johan H. C. Reiber1  
1Division of Image Processing, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, The Netherlands 

2Department of Cardiology, Chinese PLA General Hospital, No. 28 Fuxin Road, Haidian District, Beijing, 100853 China 

3Department of Cardiology, Aarhus University Hospital, Skejby, Denmark 

4Department of Cardiovascular Diseases, University Hospitals Leuven, Leuven, Belgium 
Bifurcation lesions are frequent and account for approximately 15–20% of all percutaneous coronary interventions (PCI) performed worldwide [^{1}, ^{2}]. The treatment remains challenging with a tendency towards increased restenosis and stent thrombosis [^{3}]. Correct assessment of bifurcation lesion anatomy, especially the ostia of branches, is essential in the choice of treatment strategy. Indeed, meticulous positioning of a sidebranch stent is of uttermost importance to ensure complete ostial lesion coverage and to limit the protrusion of the stent in the main vessel. Currently, Xray coronary angiography is predominantly used in daily routine to establish the diagnosis and guide PCI. The conventional approach for diagnostic angiography uses a rigid set of multiple standard angiographic views [^{4}], while the modern approach requires immediate interpretation of the first angiographic images, followed by the acquisition of those views that maximally expose the lesion severity and preferably with minimal overlap and foreshortening. In order to obtain the optimal views, operators will interactively adjust the rotation angle (left anterior oblique/right anterior oblique, LAO/RAO) and the angulation angle (Cranial/Caudal) guided by the Xray images. This “trialanderror” approach could significantly increase the volume of contrast medium used and the radiation exposure to the patient and staff. Besides, due to the variable anatomy of each individual patient combined with the variable orientation of the heart in the thorax, the chosen angle can be quite different from the true optimal viewing angle [^{5}, ^{6}].
Recently developed threedimensional quantitative coronary angiography (3D QCA) systems enabled the automated determination of bifurcation optimal viewing angles, i.e., the angle characterized by having an orthogonal view of the bifurcation including the ostium, minimizing the vessel foreshortening and overlap [^{7}]. However, this orthogonal view is uniquely determined by the anatomy of the individual bifurcation. Due to the mechanical constraints of the Xray systems, this anatomydefined bifurcation optimal viewing angle (ABOVA) might have deep angles, which possibly cannot be reached by the Carm or might be associated with an unacceptable radiation exposure to the operator. In addition, the possible overlap by other major coronary arteries could significantly influence the visualization of the bifurcation, rendering such an ABOVA less useful [^{5}]. Therefore, second best or, obtainable bifurcation optimal viewing angle (OBOVA) has to be used as an alternative to resolve the aforementioned limitations. This study assessed the distributions of ABOVA and OBOVA using threedimensional quantitative coronary angiography (3D QCA) in four main coronary bifurcations. The proximal bifurcation angle, i.e., the takeoff angle, and the distal bifurcation angle, i.e., the carina angle, at the enddiastolic (ED) phase in these four main coronary bifurcations were also assessed and compared.
A total of 187 patients with obstructive coronary bifurcation disease in four main coronary bifurcations (LM/LAD/LCx, LAD/Diagonal, LCx/OM, and PDA/PLA) were retrospectively included in this study at three medical centers (Department of Cardiology, Chinese PLA General Hospital, Beijing, China; Department of Cardiology, Aarhus University Hospital, Skejby, Aarhus, Denmark; and Department of Cardiovascular Diseases, University Hospitals Leuven, Leuven, Belgium). Inclusion criteria were: (1) Xray angiographic images were acquired by digital image intensifiers (flatpanel systems); (2) Two angiographic projections at least 25° apart with the lumen well filled with contrast dye were recorded before the target bifurcation was revascularized; and (3) The bifurcation was not totally occluded.
Angiographic images were recorded by different Xray systems (AXIOMArtis, siemens medical systems, Erlangen, Germany; AlluraXper, philips medical systems, Best, The Netherlands; and Innova 3100, GE Medical Systems, USA). Xray images were stored in DICOM format at a resolution of 512 × 512 or 1,024 × 1,024 pixels. All parameters required by the 3D angiographic reconstruction were automatically recorded by the Xray systems.
An optimal viewing angle in the Xray angiographic systems consists of two parts: rotation angle (LAO/RAO) and angulation angle (Cranial/Caudal). In this study, the viewing angle was defined as not reachable by the Carm if the rotation angle was larger than 90 LAO or 50 RAO, or if the angulation angle was larger than 40 Cranial or 40 Caudal.
Threedimensional angiographic reconstruction was performed using a novel and validated 3D QCA software package (prototype version, Medis medical imaging systems bv, Leiden, The Netherlands) [^{8}, ^{9}]. The 3D bifurcation reconstruction procedure consisted of the following steps: (1) two image sequences acquired at two arbitrary angiographic views with projection angles at least 25° apart were loaded; (2) properly contrastfilled ED frames of these angiographic image sequences were selected; (3) one to three anatomical markers, e.g., bifurcations, were identified as reference points in the two angiographic views for the automated correction of angiographic system distortions [^{7}]; (4) the target bifurcation was defined and automated 2D lumen edge detection was performed using our extensively validated QCA algorithms [^{10}, ^{11}]; and (5) automated 3D reconstruction and modeling techniques were performed. The resulting bifurcation surface modeled with beanshape crosssections in the bifurcation core and elliptical crosssections in the three segments was generated and visualized in a colorcoded fashion. Bifurcation angles and a list of optimal viewing angle candidates including the ABOVA were automatically reported. The ABOVA was characterized by having an orthogonal view of the bifurcation [^{7}], and in such a way that the foreshortening and overlap between the main vessel and the sidebranch at the ostium were minimized. However, overlaps by other major coronary arteries could still deteriorate the quality of the projection when using ABOVA as the projection angle. Therefore, in a next step, a novel overlap prediction algorithm described in our previous study [^{5}] was used to predict the overlap condition.
An example of correcting system distortions in the image geometry for the 3D angiographic reconstruction is given in Fig. 1. The two bifurcations in the left anterior descending artery (LAD) were identified as reference points and their epipolar lines, being the projection of the Xray beam directed towards a particular point on one of the projections onto the second projection [^{12}], were superimposed in the two angiographic views by Fig. 1a, b. Due to the system distortions, the epipolar lines did not go through their corresponding reference points. Figure 1a’, b’ show the results after the automated correction of system distortions: The epipolar lines now go right through their corresponding reference points in both angiographic views, demonstrating the success of this automated procedure.
Figure 2 shows the two angiographic views with the overlap prediction results and the reconstructed LAD/Diagonal bifurcation in 3D. Figure 2a, b show the two angiographic views (15 RAO, 33 Cranial and 31 LAO, 31 Cranial) with lumen contours superimposed on the LAD/Diagonal bifurcation and the result of the overlap prediction at ABOVA, being 7 RAO, 55 Cranial. The two trajectories (blue lines) in A and B did not intersect with the same region of any major coronary artery in the two angiographic views, indicating that there was no overlap between the obstructed subsegment of the LAD and other major coronary arteries at ABOVA. C shows the reconstructed LAD/Diagonal bifurcation at ABOVA. The proximal and distal bifurcation angles were 161° and 57°, respectively. The subsegment of the LAD between the two green markers had a length of 14.9 mm in 3D and a foreshortening of 4.9% at ABOVA. The overlap between the LAD and the Diagonal at the ostium was minimal. However, despite the fact that this ABOVA is characterized by minimal foreshortening and overlap, this ABOVA cannot be reached by the Carm for practical, mechanical reasons. Therefore, a second best or, another obtainable viewing angle with limited foreshortening and minimal overlap was selected from the list of optimal viewing angle candidates as OBOVA. In this case, 9 LAO, 40 Cranial was chosen as OBOVA and the LAD/Diagonal bifurcation at OBOVA is shown in C. Although the subsegment of the LAD had more foreshortening at OBOVA as compared with ABOVA (11.4 vs. 4.9%), the overlap between the LAD and the diagonal at the ostium was still minimal. Figure 2a’, b’ show the overlap prediction result for the subsegment with other unreconstructed coronary arteries. The shifting centerlines (red curves) along the trajectories (blue lines) in the two angiographic views did not intersect with any major coronary artery at the same time, indicating that there was no overlap between the subsegment of the LAD and other major coronary arteries at OBOVA. In other words, OBOVA was associated with minimal overlap and slightly more foreshortening as compared with ABOVA. However, a very important practical issue is that it can be reached by the Xray systems.
The 3D angiographic reconstruction and analyses were performed independently by four welltrained 3D QCA analysts. To guarantee the reliability of the 3D bifurcation reconstruction, all reconstruction results were reviewed by one experienced 3D QCA analyst. If the results were considered unreliable, the cases were excluded. Unreliability was mainly caused by: (1) The anatomical markers, e.g., bifurcations, used to correct system distortions were not accurately identified in the two angiographic images due to vessel overlap; (2) Suboptimal correspondence between the two angiographic views was established when the socalled perspective viewing angle, i.e., the angle between the epipolar line and the longaxis of the vessel [^{8}], was almost zero for the entire vessel segment.
Quantitative data were presented as mean difference ± standard deviation. Due to the unique anatomy of the left main bifurcation, the comparison of bifurcation angles among the four main coronary bifurcations (groups) was performed by the following procedure: The left main bifurcation group was compared with each of the other three groups using MannWhitney U test. In addition, Kruskal–Wallis U test was used initially to test the overall equality of means in the other three groups. Multiple pairwise comparisons of group means were then carried out using MannWhitney U test. A 2sided Pvalue of <0.05 was considered to be significant. All statistical analyses were carried out using SPSS software package (PASW version 18.0.0, 2009; SPSS Inc, Chicago, IL, USA.).
A total of 200 bifurcations with obstructive coronary disease were included for analysis. Of all, the analyses of six bifurcations were excluded since the reliability of the 3D bifurcation reconstruction was not approved by the experienced 3D QCA analyst, resulting in a total of 194 bifurcations from 181 patients in the final analyses. Baseline characteristics are given in Table 1. In short, the assessed bifurcations included 49 (25.3%) LM/LAD/LCx, 51 (26.3%) LAD/Diagonal, 51 (26.3%) LCx/OM, 43 (22.2%) PDA/PLA. The ostium of the daughter branches was involved in 147 (75.8%) (main vessel) and 112 (57.7%) (sidebranch).
The overlap of the bifurcation with other major coronary arteries at ABOVA was uncommon. Only 3 PDA/PLA bifurcations had overlap with the proximal right coronary artery (RCA), while the other three main coronary bifurcations had no overlap when projected at ABOVA. However, ABOVA could not be reached in 110 (56.7%) of the cases; being 40 (81.6%), 40 (78.4%), 9 (17.6%), and 21 (48.8%) cases for LM/LAD/LCx, LAD/Diagonal, LCx/OM, and PDA/PLA, respectively. Figures 3 and 4 show the distributions of ABOVA and OBOVA in the four main coronary bifurcations, respectively. Quantitative data are presented in Table 2. Both ABOVA and OBOVA distributed sparsely with large ranges of variation for all the main coronary bifurcations: LM/LAD/LCx, 5 ± 33 RAO, 47 ± 35 Caudal versus 4 ± 39 LAO, 35 ± 16 Caudal; LAD/Diagonal, 4 ± 38 RAO, 50 ± 14 Cranial versus 14 ± 28 LAO, 33 ± 5 Cranial; LCx/OM, 21 ± 32 LAO, 27 ± 17 Caudal versus 18 ± 31 LAO, 25 ± 13 Caudal; PDA/PLA, 34 ± 21 LAO, 36 ± 21 Cranial vs 28 ± 25 LAO, 29 ± 15 Cranial.
The bifurcation angles could not be calculated in four cases of the left main bifurcations due to a very short left main trunk. In the remaining 190 bifurcations, the proximal bifurcation angle (PBA) in LM/LAD/LCx was smaller than any of the other three bifurcations, being 128° ± 24° versus 151° ± 13° (P < 0.001) in LAD/Diagonal, 146° ± 18° (P < 0.001) in LCx/OM, and 145° ± 19° (P = 0.001) in PDA/PLA, respectively. The distal bifurcation angle (DBA) in LM/LAD/LCx was larger than any of the other three bifurcations, being 80° ± 21°versus 48° ± 16°(P < 0.001) in LAD/diagonal, 57° ± 16° (P < 0.001) in LCx/OM, and 59° ± 17° (P < 0.001) in PDA/PLA, respectively. The PBAs in LAD/diagonal, LCx/OM, and PDA/PLA were not statistically different (P = 0.133). However, the DBA in LAD/Diagonal was smaller as compared with LCx/OM (P = 0.004) and PDA/PLA (P = 0.001), while the DBAs in LCx/OM and PDA/PLA were not statistically different (P = 0.673).
This study found that both ABOVA and OBOVA distributed sparsely with large ranges of variation in all main coronary bifurcations, indicating that there are no fixed views that can uniformly optimize the visualization of the main coronary bifurcations. The true bifurcation optimal view is subject to the unique anatomy of each individual bifurcation. Given the fact that the viewing angles should be within the reach of the Xray systems, the optimal view for the left main bifurcation distributes mainly at the Caudal view (35 ± 16 Caudal) but spreads across the LAO/RAO view (4 ± 39 LAO); the optimal view for LAD/Diagonal distributes mainly at the Cranial view (33 ± 5 Cranial), but spreads across the LAO/RAO view (14 ± 28 LAO); the optimal view for LCx/OM distributes mainly at the Caudal view (25 ± 13 Caudal), but spreads across the LAO/RAO view (18 ± 31 LAO); the optimal view for PDA/PLA distributes mainly at the Cranial view (29 ± 15 Cranial) and the LAO view (28 ± 25).
Threedimensional quantitative coronary angiography based on routine angiographic projections has emerged as a surrogate to determine optimal viewing angles in the catheterization laboratory. Green [^{6}] evaluated 156 vessel segments and found that vessel foreshortening ranged from 0 to 50% in the expertrecommended views, while the computergenerated optimal views had only 0.5 ± 1.2% foreshortening and less than 2% overlap. Tu [^{5}] evaluated 67 target vessels by applying a novel overlap prediction approach to avoid overlap in the target vessels and found that the expert viewing angle (EVA) was associated with much more foreshortening as compared with the software viewing angle (SVA), being 8.9 ± 8.2% versus. 1.6 ± 1.5% (P < 0.001). The success of SVA with respect to EVA was also evaluated by two experienced interventional cardiologists and the results were clearly in favor of SVA. Despite the fact that promising results were demonstrated by this new imaging technique, it should be borne in mind that these results were only applied to straight vessels and hence cannot directly be transferred to the more complex bifurcation anatomy [^{13}]. The automated assessment of vessel foreshortening depends on the type of lesion and the number of affected segments. For correct assessment of lesion severity and subsequent precise stent positioning, it might be more critical to minimize overlap between the main vessel and the sidebranch at the ostium.
In a recent study, Tu [^{3}] proposed to use the orthogonal view of the bifurcation as the bifurcation optimal view, since it minimizes the foreshortening and overlap at the ostium. In addition, atherosclerotic plaques occur preferably at the outer lateral wall of the bifurcation, i.e., the site opposite to the carina, where flow is more turbulent and endothelial shear stress is lower. When plaques do involve the carina, they are likely to develop at a later stage of atherosclerosis, as a result of circumferential plaque expansion from the lateral wall [^{14}]. Therefore, the orthogonal viewing angle, i.e., ABOVA, might also expose the lesion severity at its maximum. Nevertheless, ABOVA only minimizes the overlap between the main vessel and the sidebranch at the ostium. Other major coronary arteries could also overlap with the target bifurcation when projected at ABOVA, possibly leading to significant impediment of the visualization of the target bifurcation. To our knowledge, the overlap between the main coronary bifurcations and other coronary arteries at ABOVA has not been documented. Therefore, in this study, we applied the overlap prediction approach to investigate whether this overlap would frequently occur in the general population. To our surprise, the overlap of the bifurcation with other major coronary arteries at ABOVA was uncommon. Only three PDA/PLA bifurcations overlapped with the proximal RCA, while the other three main coronary bifurcations had no overlap when projected at ABOVA. This finding further enforces the usefulness of ABOVA. However, due to the mechanical constraints of the current Xray systems, ABOVA could not be reached in 56.7% of the population. This occurred more frequent in LM/LAD/LCx (81.6%) and LAD/Diagional (78.4%), followed by PDA/PLA (48.8%) and was uncommon in LCx/OM (17.6%). These data suggest that in about half of the population, a second optimal view, i.e., OBOVA, should be used as an alternative by the current Xray systems. When choosing the second optimal view, priority should be given to minimize the overlap between the main vessel and the sidebranch at the ostium and to maximally expose the lesion severity. In other words, OBOVA for the bifurcation might not be the view elongating the ostial segments at the maximum.
To date, very limited evidence regarding with the use of bifurcation optimal viewing angles in coronary angiography is available in literature. Schlundt [^{15}] demonstrated a case in which sidebranch stenting was performed using the online 3D reconstruction of the LAD/Diagonal bifurcation to obtain the optimal view with minimal foreshortening and overlap. Sadamatsu [^{16}] reconstructed 18 left main bifurcations in 3D and selected the optimal views based on foreshortening and overlap. The authors reported that the optimal views were superior to the routine projections in all cases. However, the views were selected to optimize the visualization of the ostial LAD, possibly neglecting the visualization of the LCx. Therefore, these views do not represent the optimal views for the left main bifurcation in the general patient population. To our knowledge, the distributions of ABOVA and OBOVA in main coronary bifurcations have not been previously documented.
Another finding of this study is that the proximal bifurcation angles (PBAs) as assessed by 3D QCA in LAD/Diagonal, LCx/OM, and PDA/PLA were very much comparable and not statistically different (P = 0.133), being 151° ± 13°, 146° ± 18°, and 145° ± 19°, respectively. However, the distal bifurcation angles (DBAs) in LAD/Diagonal was smaller than LCx/OM (P = 0.004) and PDA/PLA (P = 0.001), being 48° ± 16° versus 57° ± 16°, and 59° ± 17°, respectively. The left main bifurcation had the smallest PBA (128° ± 24°) and the largest DBA (80° ± 21°).
Bifurcation angle is an important baseline anatomical characteristic for many randomized bifurcation studies [^{17}]. At present, however, bifurcation angles have been quantified mainly on the basis of 2D angiographic images, entailing great dependence on the angiographic viewing angle. 3D QCA was proposed to overcome this limitation by measuring the angles in 3D. Tu showed in a bench study that 3D QCA was able to measure bifurcation angles with high accuracy and low variability on a wide range of acquisitions angles [^{4}]. In this study the same 3D QCA software package was used to assess the bifurcation angles in vivo. Our results are very similar to a previous study by Pflederer [^{18}] who evaluated the natural distribution of DBA in 100 patients using multidetector computer tomography (80° ± 27° in LM/LAD/LCx, 46° ± 19° in LAD/Diagonal, 48° ± 24° in LCx/OM, and 53° ± 27° in PDA/PLA). However, another study by Girasis [^{17}] evaluated 266 left main bifurcations using another 3D QCA software package and reported smaller PBA (105.9° ± 21.7°) and larger DBA (95.6° ± 23.6°), as compared with our results. This can be explained by differences in patients and 3D QCA software packages. Since 3D bifurcation reconstruction based on routine angiographic projections needs to correct for various system distortions in vivo [^{3}], different software packages addressing this issue in different approaches might generate discrepancy in the assessed dimensions. In addition, there is no official guideline in the acquisition of angiographic images dedicated for 3D QCA in a broad clinical setting, making the interpretation of different clinical studies difficult.
The study is clearly limited by its retrospective in vivo design. It could therefore not assess whether the applications of bifurcation optimal viewing angles reduced radiation exposure and the volume of contrast medium used, nor improved the diagnosis and outcome of interventional procedures. Further prospective studies and randomized clinical trials are warranted before definite conclusions on the added clinical value of softwareguided bifurcation optimal viewing angles can be drawn.
Large variabilities in optimal viewing angles existed for all main coronary bifurcations. The anatomydefined bifurcation optimal viewing angle could not be reached in vivo in roughly half of the cases due to the mechanical constraints of current Xray systems. Obtainable bifurcation optimal viewing angle should be provided as an alternative or second best. The bifurcation angles in the left main bifurcation demonstrated the largest variabilities.
Notes
Shengxian Tu and Jing Jing equally contributed to the writing of the manuscript.
Shengxian Tu is employed by Medis medical imaging systems bv and has a research appointment at the Leiden University Medical Center (LUMC). Johan H. C. Reiber is the CEO of Medis medical imaging systems bv, and has a parttime appointment at LUMC as Prof of Medical Imaging.
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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ABOVA  Anatomydefined bifurcation optimal viewing angle 
DBA  Distal bifurcation angle 
DICOM  Digital imaging and communications in medicine 
ED  Enddiastolic 
EVA  Expert viewing angle 
LAD  Left anterior descending 
LAO  Left anterior oblique 
LCx  Left circumflex artery 
LM  Left main 
OBOVA  Obtainable bifurcation optimal viewing angle 
OM  Obtuse marginal 
PBA  Proximal bifurcation angle 
PCI  Percutaneous coronary interventions 
PDA  Posterior descending artery 
PLA  Posterolateral artery 
QCA  Quantitative coronary angiography 
RAO  Right anterior oblique 
RCA  Right coronary artery 
SVA  Software viewing angle 
Figures
Tables
Baseline characteristics
Patient  n = 181 
Age  61 (39–88) 
Male/female  145/36 
Bifurcation  n = 194 
LM/LAD/LCx  49 (25.3%) 
LAD/Diagonal  51 (26.3%) 
LCx/OM  51 (26.3%) 
PDA/PLA  43 (22.2%) 
Lesion classifications^{a}  
(1,0, 0)  14 (7.2%) 
(0, 1, 0)  35 (18.0%) 
(0, 0, 1)  14 (7.2%) 
(1,1,0)  33 (17.0%) 
(1,0, 1)  19 (9.8%) 
(0, 1, 1)  23 (11.9%) 
(1, 1, 1)  56 (28.9%) 
LM left main, LAD left anterior descending, LCx left circumflex artery, OM obtuse marginal, RCA right coronary artery, PDA posterior descending artery, PLA posterolateral artery
^{a}Medina classification by visual assessment
Bifurcation dimensions assessed by 3D quantitative coronary angiography
ABOVA  OBOVA  BA  

Rotation^{a}  Angulation^{b}  Rotation^{a}  Angulation^{b}  PBA  DBA  
LM/LAD/LCx  5 ± 33  47 ± 35  −4 ± 39  35 ± 16  128 ± 24^{c}  80 ± 21 
LAD/Diagonal  4 ± 38  −50 ± 14  −14 ± 28  −33 ± 5  151 ± 13  48 ± 16 
LCx/OM  −21 ± 32  27 ± 17  −18 ± 31  25 ± 13  146 ± 18  57 ± 16 
PDA/PLA  −34 ± 21  −36 ± 21  −28 ± 25  −29 ± 15  145 ± 19  59 ± 17 
ABOVA anatomydefined bifurcation optimal view angle, OBOVA obtainable bifurcation optimal viewing angle, BA bifurcation angle, PBA proximal bifurcation angle, DBA distal bifurcation angle
^{a}Positive value represents right anterior oblique and negative value represents left anterior oblique
^{b}Positive value represents Caudal and negative value represents Cranial
^{c}Angle between LM and LCx
Article Categories:
Keywords: Keywords Coronary artery disease, Quantitative coronary angiography, Threedimensional reconstruction, Xray angiography. 
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