S.-Y. James Chen

3D coronary reconstruction from routine single-plane coronary angiograms: clinical validation and quantitative analysis of the right coronary artery in 100 patients.

Background: Current coronary angiographic techniques display complex three-dimensional (3D) coronary structures in two dimensions (2D). We have developed a 3D reconstruction (3DR) algorithm using standard single-plane angiographic images that allows for 3D display of coronary structures. The purpose of this study was to validate our 3DR algorithm and quantify anatomic characteristics of the right coronary artery (RCA) in vivo. Methods: Accuracy and reproducibility studies were performed using 3DRs of a coronary phantom and in vivo following 3DRs in 40 patients. The anatomic features of the RCA were then quantified in 100 patients. Results: Comparison of length and bifurcation angles (BA) from the phantom to the 3DRs revealed good accuracy and correlation for both (r = 0.95 and 0.93 respectively), with diameter error of <7%. In vivo, the average root mean square (RMS) error in the spatial coordinates of the vessel centerlines was 3.12 ± 0.77 and 3.16 ± 0.75 mm in 20 left coronary arteries (LCA) and 20 RCAs respectively. Interobserver average RMS error was 3.47 ± 1.96 mm and intraobserver average RMS error was 3.02 ± 1.07 and 3.44 ± 1.57 mm for two different operators (p = NS). The average RCA length was 10.2 ± 1.7 cm, average radius of curvature (ROC) was 52 ± 9°, and the average 3D bifurcation angle of the posterior descending artery (PDA) from the RCA was 55 ± 22°. Foreshortening (FS) of the segments of the RCA in three standard’ projections ranged from 0–60, 0–75, and 0–82% respectively. Conclusions: Using our 3DR algorithm patient-specific anatomic characteristics can be accurately displayed and quantified, expanding the information that can be derived from routine coronary angiography.

Three-Dimensional Analysis of in vivo Coronary Stent – Coronary Artery Interactions

Stent implantation results in important three-dimensional (3D) changes in arterial geometry which may be associated with adverse events. Previous attempts to quantify these 3D changes have been limited by two-dimensional techniques. Using a 3D reconstruction technique, vessel curvatures at end-diastole (ED) and end-systole (ES) were measured before and after stent placement of 100 stents (3 stent cell designs, 6 stent types). After stenting, the mean curvature at ED and ES decreased by 22 and 21%, respectively, and represents a straightening effect on the treated vessel. This effect was proportional to the amount of baseline curvature as high vessel curvature predicted more profound vessel straightening. When analyzed by stent cell design, closed-cell stents resulted in more vessel straightening than other designs (open cell or modified slotted tubes). Stent implantation resulted in the transmission of shape changes to stent ends and generated hinge points or buckling. Stent implantation creates 3D changes in arterial geometry which can be quantified using a 3D reconstruction technique.

Initial clinical experience of selective coronary angiography using one prolonged injection and a 180° rotational trajectory

Evaluate the safety of prolonged coronary injections during a rotational acquisition covering 180°.

Safety and efficacy of dual-axis rotational coronary angiography vs. standard coronary angiography.

Objective: To determine the safety and efficacy of dual‐axis rotational coronary angiography (DARCA) by directly comparing it to standard coronary angiography (SA). Background: Standard coronary angiography (SA) requires numerous fixed static images of the coronary tree and has multiple well‐documented limitations. Dual‐axis rotational coronary angiography (DARCA) is a new rotational acquisition technique that entails simultaneous LAO/RAO and cranial/caudal gantry movement. This technological advancement obtains numerous unique images of the left or right coronary tree with a single coronary injection. We sought to assess the safety and efficacy of DARCA as well as determine DARCAs adequacy for CAD screening and assessment. Methods: Thirty patients underwent SA following by DARCA. Contrast volume, radiation dose (DAP) and procedural time were recorded for each method to assess safety. For DARCA acquisitions, blood pressure (BP), heart rate (HR), symptoms and any arrhythmias were recorded. All angiograms were reviewed for CAD screening adequacy by two independent invasive cardiologists. Results: Compared to SA, use of DARCA was associated with a 51% reduction in contrast, 35% less radiation exposure, and 18% shorter procedural time. Both independent reviewers noted DARCA to be at least equivalent to SA with respect to the ability to screen for CAD. Conclusion: DARCA represents a new angiographic technique which is equivalent in terms of image quality and is associated with less contrast use, radiation exposure, and procedural time than SA.

Rotational vs. standard coronary angiography: An image content analysis

Objective: To evaluate the clinical utility of images acquired from rotational coronary angiographic (RA) acquisitions compared to standard “fixed” coronary angiography (SA). Background: RA is a novel angiographic modality that has been enabled by new gantry systems that allow calibrated automatic angiographic rotations and has been shown to reduce radiation and contrast exposure compared to SA. RA provides a dynamic multiple‐angle perspective of the coronaries during a single contrast injection. Methods: The screening adequacy, lesion assessment, and a quantitative coronary analysis (QCA) of both SA and RA were compared by independent blinded review in 100 patients with coronary artery disease (CAD). Results: SA and RA recognize a similar total number of lesions (P = 0.61). The qualitative assessment of lesion characteristics and severity between modalities was comparable and lead to similar clinical decisions. Visualization of several vessel segments (diagonal, distal RCA, postero‐lateral branches and posterior‐descending) was superior with RA when compared to SA (P < 0.05). A QCA comparison (MLD, MLA, LL, % DS) revealed no difference between SA and RA. The volume of contrast (23.5 ± 3.1 mL vs. 39.4 ± 4.1; P = 0.0001), total radiation exposure (27.1 ± 4 vs. 32.1 ± 3.8 Gycm2; P = 0.002) and image acquisition time (54.3 ± 36.8 vs. 77.67 ± 49.64 sec; P = 0.003) all favored RA. Conclusion: Coronary lesion assessment, coronary screening adequacy, and QCA evaluations are comparable in SA and RA acquisition modalities in the diagnosis of CAD however RA decreases contrast volume, image acquisition time, and radiation exposure.

Four-dimensional analysis of cyclic changes in coronary artery shape.

The objective of this study was to derive a method for quantifying the dynamic geometry of coronary arteries. Coronary artery geometry plays an important role in atherosclerosis. Coronary artery geometry also influences the performance of coronary interventions. Conversely, implantation of stents may alter coronary artery geometry. Clinical tools to define vessel shape have not been readily available. Using a Frenet‐Serret curvature analysis applied to 3D reconstruction data derived from standard coronary angiograms, 21 coronary arteries were analyzed at end‐diastole (ED) and end‐systole (ES). Vessels were divided anatomically: type 1 consisted of vessels lying in the AV groove (left circumflex, right coronary) and type 2 consisted of vessels overlying actively contracting myocardium (left anterior descending, diagonal, obtuse marginal, right ventricular marginal, posterior descending, posterolateral). Vessel segments were analyzed by assessing the changes in curvature, torsion, and discrete flexion points (FPs), areas of systolic bending in the arterial contour. The curvature from ED to ES of type 1 vessels was unchanged (−0.02 ± 0.03 cm−1), while the curvature change of type 2 vessels showed a 38% increase (0.33 ± 0.04 cm−1; P < 0.001). Type 1 vessels had fewer FPs per vessel than type 2 vessels (0.38 ± 0.18 and 2.40 ± 0.23 FP/vessel, respectively; P < 0.001). FPs were more common in distal segments and branch vessels. A method to quantify cyclic changes in coronary artery shape was applied to 3D data sets derived from standard coronary angiograms. Coronary arteries undergo a cyclic change in shape resulting in changes in overall curvature as well as formation of discrete flexion points. These changes in vessel shape are asymmetrically distributed in coronary arteries. Cathet Cardiovasc Intervent 2002;55:344–354.

Stress analysis using anatomically realistic coronary tree.

Plaque rupture with superimposed thrombosis is the main cause of the acute coronary syndromes of unstable angina, myocardial infarction, and sudden death. Endothelial disruption leading to plaque rupture may relate to mechanical fatigue associated with cyclic flexion of plaques. A novel method is proposed to assess stress and strain distribution using the finite element (FE) analysis and in vivo patient-specific dynamic 3D coronary arterial tree reconstruction from cine angiographic images. The local stresses were calculated on the diseased arterial wall which was modeled as consisting of a central fibrotic cap subjected to the cyclic flexion from cardiac contraction. Various parameters characterizing the plaque were chosen including vessel diameter, percentage narrowing, and lesion length. According to the FEA simulations, the results show that the smaller vessel diameter, greater percentage narrowing, and/or larger lesion size may result in higher stress on the plaque cap, with the vessel diameter as the dominant factor.

Computer Assisted Coronary Intervention by Use of On-line 3d Reconstruction and Optimal View Strategy

A novel method has been developed for on-line reconstruction of the 3D coronary arterial tree based on a pair of routine angiograms acquired from any two arbitrary viewing angles using a single-plane or biplane imaging system. An arterial segment of interest (e.g., coronary stenosis) is selected on the projection of reconstructed 3D coronary model. Afterwards, the process of optimal view strategy is employed resulting in foreshortening, overlap, and composite maps relative to the selected arterial segment by which any computer-generated projection associated with the gantry orientation can be previewed. By use of the three maps, the views with minimal foreshortening and vessel overlap for the selected arterial segment of interest can be determined to guide subsequent angiogram acquisitions for interventional procedure. More than 200 cases of coronary arterial systems have been reconstructed. A validation confirmed the accuracy of 3D length measurement to within RMS 3.1% error using 8 pairs of angiograms of intra-coronary catheter wire of 105 mm length.

In vivo 3D modeling of the femoropopliteal artery in human subjects based on x-ray angiography : Methodology and validation

Endovascular revascularization of the femoropopliteal (FP) artery has been limited by high rates of restenosis and stent fracture. The unique physical forces that are applied to the FP artery during leg movement have been implicated in these phenomena. The foundation for measuring the effects of physical forces on the FP artery in a clinically relevant environment is based on the ability to develop 3D models of this vessel in different leg positions in vivo in patients with peripheral arterial disease (PAD). By acquiring paired angiographic images of the FP artery, and using angiography-based 3D modeling algorithms previously validated in the coronary arteries, the authors generated 3D models of ten FP arteries in nine patients with PAD with the lower extremity in straight leg (SL) and crossed leg (CL) positions. Due to the length of the FP artery, overlapping paired angiographic images of the entire FP artery were required to image the entire vessel, which necessitated the development of a novel fusion process in order to generate a 3D model of the entire FP artery. The methodology of angiographic acquisition and 3D model generation of the FP artery is described. In a subset of patients, a third angiographic view (i.e., validation view) was acquired in addition to the standard paired views for the purpose of validating the 3D modeling process. The mean root-mean-square (rms) error of the point-to-point distances between the centerline of the main FP artery from the 2D validation view and the centerline from the 3D model placed in the validation view for the SL and CL positions were 0.93 +/- 0.19 mm and 1.12 +/- 0.25 mm, respectively. Similarly, the mean rms error of the same comparison for the main FP artery and sidebranches for the SL and CL positions were 1.09 +/- 0.38 mm and 1.21 +/- 0.25 mm, respectively. A separate validation of the novel fusion process was performed by comparing the 3D model of the FP artery derived from fusion of 3D models of adjacent FP segments with the 2D validation view incorporating the region of fusion. The mean rms error of vessel centerline points of the main FP artery, the main FP artery plus directly connected sidebranches, and the mean rms error of upstream, downstream, and sidebranch directional vectors at bifurcation points in the overlap region were 1.41 +/- 0.79 mm, 2.13 +/- 1.12 mm, 3.16 +/- 3.72 degrees, 3.60 +/- 5.39 degrees, and 8.68 +/- 8.42 degrees in the SL position, respectively, and 1.29 +/- 0.35 mm, 1.61 +/- 0.78 mm, 4.68 +/- 4.08 degrees, 3.41 +/- 2.23 degrees, and 5.52 +/- 4.41 degrees in the CL position, respectively. Inter- and intraobserver variability in the generation of 3D models of individual FP segments and the fusion of overlapping FP segments were assessed. The mean rms errors between the centerlines of nine 3D models of individual FP segments generated by two independent observers, and repeated measurement by the same observer were 2.78 +/- 1.26 mm and 3.50 +/- 1.15 mm, respectively. The mean rms errors between the centerline of four 3D models of fused overlapping FP segments generated by two independent observers, and repeated measurement by the same observer were 4.99 +/- 0.99 mm and 5.98 +/- 1.22 mm, respectively. This study documents the ability to generate 3D models of the entire FP artery in vivo in patients with PAD in both SL and CL positions using routine angiography, and validates the methodologies used.

Coronary Intervention Planning Using Hybrid 3D Reconstruction

A new method is presented to assist the clinician in planning a interventional procedure while the patient is already on the catheterization table. Based on several ECG-selected projections from a rotational X-ray acquisition, both a volumetric cone-beam reconstruction of the coronary tree as well as a three-dimensional surface model of the vessel segment of interest are generated. The proposed method provides the clinician with the length and diameters of the vessel segment of interest as well as with an ’optimal working view’. In this view, the gantry is positioned such that the vessel segment of interest is the least foreshortened and vessel overlap is minimized during the entire heart cycle. Examples on a phantom object and on patient data demonstrate the accuracy and feasibility of the approach.