Kinematic and deformation analysis of 4-D coronary arterial trees reconstructed from cine angiograms

Impact of Stenting on PDA Length, Curvature, and Pulsatile Deformations Based on CT Assessment

Background

We sought to investigate the impact of stenting on native patent ductus arteriosus (PDA) length, curvature, and pulsatile deformations in patients with ductal-dependent pulmonary circulations.

Methods

Patients with PDA stents who received contrast-enhanced 3-dimensional computed tomography with a view of the PDA, thoracic aorta, and pulmonary arteries were retrospectively included in this study. Geometric models of the prestented and poststented PDA were constructed from the computed tomography images, and PDA arclength, curvature, and pulsatile deformations were quantified.

Results

A total of 12 patients with cyanotic congenital heart disease were included, 10 of whom received 1 stent in the PDA and 2 received multiple overlapping stents. From prestenting to poststenting, the PDA shortened by 26 ± 18% (P = .004) and decreased in mean and peak curvature by 60 ± 21% and 68 ± 15%, respectively (both P < .001). Pulsatile deformations varied highly for the native PDA, stented PDA, and stents themselves.

Conclusions

The shortening and straightening of the PDA after stenting are significant and substantial, and their quantitative characterization will enable interventionalists to select stent lengths that span the entire PDA without encroaching on the aortic or pulmonary artery, which could cause hemodynamic interference, stent kink, and fatigue. Pulsatile PDA deformations can be used to design and evaluate devices tailored to congenital heart disease in neonates.

Self-calibration of C-arm imaging system using interventional instruments during an intracranial biplane angiography

Purpose

To create an accurate 3D reconstruction of the vascular trees, it is necessary to know the exact geometrical parameters of the angiographic imaging system. Many previous studies used vascular structures to estimate the system’s exact geometry. However, utilizing interventional devices and their relative features may be less challenging, as they are unique in different views. We present a semi-automatic self-calibration approach considering the markers attached to the interventional instruments to estimate the accurate geometry of a biplane X-ray angiography system for neuroradiologic use.

Methods

A novel approach is proposed to detect and segment the markers using machine learning classification, a combination of support vector machine and boosted tree. Then, these markers are considered as reference points to optimize the acquisition geometry iteratively.

Results

The method is evaluated on four clinical datasets and three pairs of phantom angiograms. The mean and standard deviation of backprojection error for the catheter or guidewire before and after self-calibration are \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7.13\pm 6.47$$\end{document}7.13±6.47 mm and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.10\pm 0.06$$\end{document}0.10±0.06 mm, respectively. The mean and standard deviation of the 3D root-mean-square error (RMSE) for some markers in the phantom reduced from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.51\pm 0.11$$\end{document}0.51±0.11 to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.31\pm 0.08$$\end{document}0.31±0.08 mm.

Conclusion

A semi-automatic approach to estimate the accurate geometry of the C-arm system was presented. Results show the reduction in the 2D backprojection error as well as the 3D RMSE after using our proposed self-calibration technique. This approach is essential for 3D reconstruction of the vascular trees or post-processing techniques of angiography systems that rely on accurate geometry parameters.

3D Reconstruction with Coronary Artery Based on Curve Descriptor and Projection Geometry-Constrained Vasculature Matching

This paper presents a novel method based on a curve descriptor and projection geometry constrained for vessel matching. First, an LM (Leveberg–Marquardt) algorithm is proposed to optimize the matrix of geometric transformation. Combining with parameter adjusting and the trust region method, the error between 3D reconstructed vessel projection and the actual vessel can be minimized. Then, CBOCD (curvature and brightness order curve descriptor) is proposed to indicate the degree of the self-occlusion of blood vessels during angiography. Next, the error matrix constructed from the error of epipolar matching is used in point pairs matching of the vascular through dynamic programming. Finally, the recorded radius of vessels helps to construct ellipse cross-sections and samples on it to get a point set around the centerline and the point set is converted to mesh for reconstructing the surface of vessels. The validity and applicability of the proposed methods have been verified through experiments that result in the significant improvement of 3D reconstruction accuracy in terms of average back-projection errors. Simultaneously, due to precise point-pair matching, the smoothness of the reconstructed 3D coronary artery is guaranteed.

A Simple Method for Automatic 3D Reconstruction of Coronary Arteries From X-Ray Angiography

Automatic three-dimensional (3-D) reconstruction of the coronary arteries (CA) from medical imaging modalities is still a challenging task. In this study, we present a deep learning-based method of automatic identification of the two ends of the vessel from X-ray coronary angiography (XCA). We also present a method of using template models of CA in matching the two-dimensional segmented vessels from two different angles of XCA. For the deep learning network, we used a U-net consisting of an encoder (Resnet) and a decoder. The two ends of the vessel were manually labeled to generate training images. The network was trained with 2,342, 1,907, and 1,523 labeled images for the left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA), respectively. For template models of CA, ten reconstructed 3-D models were averaged for each artery. The accuracy of correspondence using template models was compared with that of manual matching. The deep learning network pointed the proximal region (20% of the total length) in 97.7, 97.5, and 96.4% of 315, 201, and 167 test images for LAD, LCX, and RCA, respectively. The success rates in pointing the distal region were 94.9, 89.8, and 94.6%, respectively. The average distances between the projected points from the reconstructed 3-D model to the detector and the points on the segmented vessels were not statistically different between the template and manual matchings. The computed FFR was not significantly different between the two matchings either. Deep learning methodology is feasible in identifying the two ends of the vessel in XCA, and the accuracy of using template models is comparable to that of manual correspondence in matching the segmented vessels from two angles.

Three-dimensional reconstruction and NURBS-based structured meshing of coronary arteries from the conventional X-ray angiography projection images

Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imaging technique in the interventional cardiology for over five decades. Accordingly, demands for tools that could increase efficiency of the XRA procedure for the quantitative analysis of coronary arteries (CA) are constantly increasing. The aim of this study was to propose a novel procedure for three-dimensional modeling of CA from uncalibrated XRA projections. A comprehensive mathematical model of the image formation was developed and used with a robust genetic algorithm optimizer to determine the calibration parameters across XRA views. The frames correspondences between XRA acquisitions were found using a partial-matching approach. Using the same matching method, an efficient procedure for vessel centerline reconstruction was developed. Finally, the problem of meshing complex CA trees was simplified to independent reconstruction and meshing of connected branches using the proposed nonuniform rational B-spline (NURBS)-based method. Because it enables structured quadrilateral and hexahedral meshing, our method is suitable for the subsequent computational modelling of CA physiology (i.e. coronary blood flow, fractional flow reverse, virtual stenting and plaque progression). Extensive validations using digital, physical, and clinical datasets showed competitive performances and potential for further application on a wider scale.

Reconstruction of coronary arteries from X-ray angiography: A review

Despite continuous progress in X-ray angiography systems, X-ray coronary angiography is fundamentally limited by its 2D representation of moving coronary arterial trees, which can negatively impact assessment of coronary artery disease and guidance of percutaneous coronary intervention. To provide clinicians with 3D/3D+time information of coronary arteries, methods computing reconstructions of coronary arteries from X-ray angiography are required. Because of several aspects (e.g. cardiac and respiratory motion, type of X-ray system), reconstruction from X-ray coronary angiography has led to vast amount of research and it still remains as a challenging and dynamic research area. In this paper, we review the state-of-the-art approaches on reconstruction of high-contrast coronary arteries from X-ray angiography. We mainly focus on the theoretical features in model-based (modelling) and tomographic reconstruction of coronary arteries, and discuss the evaluation strategies. We also discuss the potential role of reconstructions in clinical decision making and interventional guidance, and highlight areas for future research.

An experimental assessment of catheter trackability forces with tortuosity parameters along patient-specific coronary phantoms

Coronary artery disease is one of the leading causes of cardiovascular deaths worldwide. Approximately 70% of patients requiring coronary revascularisation receive endovascular stents. The endovascular procedure is the preferred option due to its minimally invasive nature when compared to open heart surgery. Stent delivery is paramount for the success of the endovascular procedure. Catheter delivery forces within tortuous blood vessels can produce vasoconstriction and injury, resulting in reactive intimal proliferation or distal embolisation associated with end-organ ischaemia and infarction. Trackability is evaluated by most medical device companies for further development of their delivery systems. Relevant device design attributes must be tested in settings which simulate aspects of the intended use conditions, such as vessel geometry and compliance. Various tortuosity parameters are used to facilitate endovascular intervention planning. This study assessed the significance and correlation between the trackability forces for a coronary stent system with various geometrical parameters based on patient-specific geometries. A motorised delivery system delivered a commercially available coronary stent system and monitored the trackability forces along three phantom patient-specific thin-walled, compliant coronary vessels supported by a cardiac phantom model. The maximum trackability forces, curvature and torsion values ranged from 0.31 to 0.87 N, 0.06 to 0.22 mm(-1) and -11.1 to 5.8 mm(-1), respectively. The trackability forces were significantly different between all vessels (p < 0.002), while the tortuosity parameters were not significantly different (p > 0.05). A new tortuosity parameter-coined tracking curvature which considers the lumen radius as well as the curvature along the centreline was statistically different (p < 0.002) for all vessels and correlated with the trackability forces. There was a strong correlation between the cumulative trackability force and the cumulative tracking curvature. Tracking curvature could be used as a predictive clinical tool to aid stent delivery to the vicinity of the lesion.

The Effects That Cardiac Motion has on Coronary Hemodynamics and Catheter Trackability Forces for the Treatment of Coronary Artery Disease: An In Vitro Assessment

The coronary arterial tree experiences large displacements due to the contraction and expansion of the cardiac muscle and may influence coronary haemodynamics and stent placement. The accurate measurement of catheter trackability forces within physiological relevant test systems is required for optimum catheter design. The effects of cardiac motion on coronary flowrates, pressure drops, and stent delivery has not been previously experimentally assessed. A cardiac simulator was designed and manufactured which replicates physiological coronary flowrates and cardiac motion within a patient-specific geometry. A motorized delivery system delivered a commercially available coronary stent system and monitored the trackability forces along three phantom patient-specific thin walled compliant coronary vessels supported by a dynamic cardiac phantom model. Pressure drop variation is more sensitive to cardiac motion than outlet flowrates. Maximum pressure drops varied from 7 to 49 mmHg for a stenosis % area reduction of 56 to 90%. There was a strong positive linear correlation of cumulative trackability force with the cumulative curvature. The maximum trackability forces and curvature ranged from 0.24 to 0.87 N and 0.06 to 0.22 mm(-1) respectively for all three vessels. There were maximum and average percentage differences in trackability forces of (23-49%) and (1.9-5.2%) respectively when comparing a static pressure case with the inclusion of pulsatile flow and cardiac motion. Cardiac motion with pulsatile flow significantly altered (p value <0.001) the trackability forces along the delivery pathways with high local percentage variations and pressure drop measurements.

Reconstruction of coronary trees from 3DRA using a 3D+t statistical cardiac prior

A 3D+t description of the coronary tree is important for diagnosis of coronary artery disease and therapy planning. In this paper, we propose a method for finding 3D+t points on coronary artery tree given tracked 2D+t point locations in X-ray rotational angiography images. In order to cope with the ill-posedness of the problem, we use a bilinear model of ventricle as a spatio-temporal constraint on the nonrigid structure of the coronary artery. Based on an energy minimization formulation, we estimate i) bilinear model parameters, ii) global rigid transformation between model and X-ray coordinate systems, and iii) correspondences between 2D coronary artery points on X-ray images and 3D points on bilinear model. We validated the algorithm using a software coronary artery phantom.

Three-dimensional elliptical reconstruction for stereoscopic magnetic resonance angiography

Stereoscopic MRA acquires a pair of blood vessel projections at two different viewing angles. Previously, we have developed two algorithms to reconstruct 3-D blood vessels from stereoscopic MRA. The assumption we made was that blood vessels were tilting circular tubes and the shape of the vessel on every cross-section was an ellipse. Since an ellipse can be represented in either algebraic form or parametric form, our previous algorithms reconstructed the ellipses by representing them in these two forms. In this paper, we further improved the accuracy of our previous algorithms by an order through two enhancements. The first improvement we made was a better method to estimate the rotation angle of the major axis of an ellipse. Instead of using the center of two adjacent ellipses to estimate the rotation angle as in our previous method, the new method used the projection lengths of the two views to estimate the angle. The second improvement we made was the equation to describe the relationship between the major/minor axes and the projection lengths. In our experiments, the average estimation error for the parametric algorithm was improved from 0.471 pixels to 0.066 pixels. The average error for the algebraic algorithm was improved from 0.101 pixels to 0.014 pixels.

In Vivo Stress Analysis of a Pacing Lead From an Angiographic Sequence

In this paper, a method is presented to analyze the mechanical stress distribution in a pacing lead based on a sequence of paired 2D angiographic images. The 3D positions and geometrical shapes of an implanted pacemaker lead throughout the cardiac cycle were generated using a previously validated 3D modeling technique. Based on the Frenet–Serret formulas, the kinematic property of the lead was derived and characterized. The distribution of curvature and twist angle per unit length in the pacing lead was calculated from a finite difference method, which enabled a rapid and effective computation of the mechanical stress in the pacing lead. The analytical solution of the helix deformation geometry was used to evaluate the accuracy of the proposed numerical method, and an excellent agreement in curvature, twist angle, and stresses was achieved. As demonstrated in the example, the proposed technique can be used to analyze the complex movement and deformation of the implanted pacing lead in vivo. The information can facilitate the future development of pacing leads.

Spatio-temporal data fusion for 3D+T image reconstruction in cerebral angiography

This paper provides a framework for generating high resolution time sequences of 3D images that show the dynamics of cerebral blood flow. These sequences have the potential to allow image feedback during medical procedures that facilitate the detection and observation of pathological abnormalities such as stenoses, aneurysms, and blood clots. The 3D time series is constructed by fusing a single static 3D model with two time sequences of 2D projections of the same imaged region. The fusion process utilizes a variational approach that constrains the volumes to have both smoothly varying regions separated by edges and sparse regions of nonzero support. The variational problem is solved using a modified version of the Gauss-Seidel algorithm that exploits the spatio-temporal structure of the angiography problem. The 3D time series results are visualized using time series of isosurfaces, synthetic X-rays from arbitrary perspectives or poses, and 3D surfaces that show arrival times of the contrasted blood front using color coding. The derived visualizations provide physicians with a previously unavailable wealth of information that can lead to safer procedures, including quicker localization of flow altering abnormalities such as blood clots, and lower procedural X-ray exposure. Quantitative SNR and other performance analysis of the algorithm on computational phantom data are also presented.

Sequential reconstruction of vessel skeletons from X-ray coronary angiographic sequences

X-ray coronary angiography (CAG) is one of widely used imaging modalities for diagnosis and interventional treatment of cardiovascular diseases. Dynamic CAG sequences acquired from several viewpoints record coronary arterial morphological information as well as dynamic performances. The aim of this work is to propose a semi-automatic method for sequentially reconstructing coronary arterial skeletons from a pair of CAG sequences covering one or several cardiac cycles acquired from different views based on snake model. The snake curve deforms directly in 3D through minimizing a predefined energy function and ultimately stops at the global optimum with the minimal energy, which is the desired 3D vessel skeleton. The energy function combines intrinsic properties of the curve and acquired image data with a priori knowledge of coronary arterial morphology and dynamics. Consequently, 2D extraction, 3D sequential reconstruction and tracking of coronary arterial skeletons are synchronously implemented. The main advantage of this method is that matching between a pair of angiographic projections in point-by-point manner is avoided and the reproducibility and accuracy are improved. Results are given for clinical image data of patients in order to validate the proposed method.

3-D reconstruction of the coronary artery tree from multiple views of a rotational X-ray angiography

To present an efficient and robust method for 3-D reconstruction of the coronary artery tree from multiple ECG-gated views of an X-ray angiography. 2-D coronary artery centerlines are extracted automatically from X-ray projection images using an enhanced multi-scale analysis. For the difficult data with low vessel contrast, a semi-automatic tool based on fast marching method is implemented to allow manual correction of automatically-extracted 2-D centerlines. First, we formulate the 3-D symbolic reconstruction of coronary arteries from multiple views as an energy minimization problem incorporating a soft epipolar line constraint and a smoothness term evaluated in 3-D. The proposed formulation results in the robustness of the reconstruction to the imperfectness in 2-D centerline extraction, as well as the reconstructed coronary artery tree being inherently smooth in 3-D. We further propose to solve the energy minimization problem using α-expansion moves of Graph Cuts, a powerful optimization technique that yields a local minimum in a strong sense at a relatively low computational complexity. We show experimental results on a synthetic coronary phantom, a porcine data set and 11 patient data sets. For the coronary phantom, results obtained using different number of views are presented. 3-D reconstruction error evaluated by the mean plus one standard deviation is below one millimeter when 4 or more views are used. For real data, reconstruction using 4 to 5 views and 256 depth labels averaged around 12 s on a computer with 2.13 GHz Intel Pentium M and achieves a mean 2-D back-projection error of 1.18 mm (ranging from 0.84 to 1.71 mm) in 12 cases. The accuracy for multi-view reconstruction of the coronary artery tree as reported from the phantom and patient studies is promising, and the efficiency is significantly improved compared to other approaches reported in the literature, which range from a few to tens of minutes. Visually good and smooth reconstruction is demonstrated.

Computer assistance for solving imaging problems

Medical imaging has moved into an era of digital files and processing of images to yield three-dimensional models and reconstructions. This development has opened up opportunities to apply computer techniques in traditional imaging tasks. Two of the most common imaging tasks are those to correct the two-dimensional projection problems of foreshortening of lesions and of vessel overlap. This article explores the use of computers to assist in these tasks, to create databases for guiding decision making, to provide graphics to assist the physician, and to simulate cardiovascular procedures.

Novel approach for 3-d reconstruction of coronary arteries from two uncalibrated angiographic images

Three-dimensional reconstruction of vessels from digital X-ray angiographic images is a powerful technique that compensates for limitations in angiography. It can provide physicians with the ability to accurately inspect the complex arterial network and to quantitatively assess disease induced vascular alterations in three dimensions. In this paper, both the projection principle of single view angiography and mathematical modeling of two view angiographies are studied in detail. The movement of the table, which commonly occurs during clinical practice, complicates the reconstruction process. On the basis of the pinhole camera model and existing optimization methods, an algorithm is developed for 3-D reconstruction of coronary arteries from two uncalibrated monoplane angiographic images. A simple and effective perspective projection model is proposed for the 3-D reconstruction of coronary arteries. A nonlinear optimization method is employed for refinement of the 3-D structure of the vessel skeletons, which takes the influence of table movement into consideration. An accurate model is suggested for the calculation of contour points of the vascular surface, which fully utilizes the information in the two projections. In our experiments with phantom and patient angiograms, the vessel centerlines are reconstructed in 3-D space with a mean positional accuracy of 0.665 mm and with a mean back projection error of 0.259 mm. This shows that the algorithm put forward in this paper is very effective and robust.

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.

Using flow information to support 3D vessel reconstruction from rotational angiography

For the assessment of cerebrovascular diseases, it is beneficial to obtain three-dimensional (3D) morphologic and hemodynamic information about the vessel system. Rotational angiography is routinely used to image the 3D vascular geometry and we have shown previously that rotational subtraction angiography has the potential to also give quantitative information about blood flow. Flow information can be determined when the angiographic sequence shows inflow and possibly outflow of contrast agent. However, a standard volume reconstruction assumes that the vessel tree is uniformly filled with contrast agent during the whole acquisition. If this is not the case, the reconstruction exhibits artifacts. Here, we show how flow information can be used to support the reconstruction of the 3D vessel centerline and radii in this case. Our method uses the fast marching algorithm to determine the order in which voxels are analyzed. For every voxel, the rotational time intensity curve (R-TIC) is determined from the image intensities at the projection points of the current voxel. Next, the bolus arrival time of the contrast agent at the voxel is estimated from the R-TIC. Then, a measure of the intensity and duration of the enhancement is determined, from which a speed value is calculated that steers the propagation of the fast marching algorithm. The results of the fast marching algorithm are used to determine the 3D centerline by backtracking. The 3D radius is reconstructed from 2D radius estimates on the projection images. The proposed method was tested on computer simulated rotational angiography sequences with systematically varied x-ray acquisition, blood flow, and contrast agent injection parameters and on datasets from an experimental setup using an anthropomorphic cerebrovascular phantom. For the computer simulation, the mean absolute error of the 3D centerline and 3D radius estimation was 0.42 and 0.25 mm, respectively. For the experimental datasets, the mean absolute error of the 3D centerline was 0.45 mm. Under pulsatile and nonpulsatile conditions, flow information can be used to enable a 3D vessel reconstruction from rotational angiography with inflow and possibly outflow of contrast agent. We found that the most important parameter for the quality of the reconstruction of centerline and radii is the range through which the x-ray system rotates in the time span of the injection. Good results were obtained if this range was at least 135 degrees. As a standard c-arm can rotate 205 degrees, typically one third of the acquisition can show inflow or outflow of contrast agent, which is required for the quantification of blood flow from rotational angiography.

Comparison of assessment of native coronary arteries by standard versus three-dimensional coronary angiography

Vessel foreshortening is a major limitation of standard coronary angiography due to the 2-dimensional representation of 3-dimensional structures. Three-dimensional models may overcome it. The aim of this study was to compare measurements of coronary segments from quantitative coronary angiography (QCA) in an operator-selected "working view" of standard 2-dimensional coronary angiography with those from 3-dimensional coronary angiography (3D-CA) reconstruction models, which are automatically generated from software applied to rotational coronary angiographic acquisitions. Patients who underwent percutaneous coronary intervention were considered. Two or 3 segments of the artery needing treatment were prespecified, using bifurcations as edges. The operator selected a working view from standard angiography as the view best representing each segment. Rotational angiography was performed, allowing 3-dimensional reconstruction of the selected segments. Additionally a marker guidewire (with 4 markers 10 mm away from one another at the distal tip) was used to further measure segment length, and it was considered the "gold standard" reference. In 36 patients, 81 segments from 12 left anterior descending, 12 circumflex, and 12 right coronary arteries were evaluated. Three-dimensional coronary angiography was always feasible. Although reference vessel diameter was not different between 3D-CA and QCA (p >0.05), segment length measurements were on average 2.3 +/- 2.5 mm longer with 3D-CA than with QCA (p <0.001) and 0.4 +/- 1.8 mm longer than with marker guidewire measurement (p = 0.047). Marker guidewire measurements were 1.9 +/- 2.8 mm longer than QCA measurements (p <0.001). According to Bland-Altman plots, 3D-CA and marker guidewire measurements had the best agreement. In conclusion, 3-dimensional coronary modeling is highly feasible and yields more accurate assessments of the lengths of coronary segments than standard QCA.

The Stretch–Compression Type of Coronary Artery Movement Predicts the Location of Culprit Lesions Responsible for ST-Segment Elevation Myocardial Infarctions

BACKGROUND

Prediction of the location of culprit lesions responsible for ST-segment elevation myocardial infarctions may allow for prevention of these events by safe and easily deliverable local therapies.

METHODS

A retrospective analysis of coronary movement was performed on coronary angiograms of patients who subsequently represented with ST-segment elevation myocardial infarction treated by primary or rescue angioplasty at a single institution.

RESULTS

Twenty patients were identified. The stretch-compression type of coronary artery movement (CAM) was a statistically significant independent predictor of the segment containing the culprit lesion (odds ratio 6.10, p-value 0.005).

CONCLUSIONS

The stretch-compression type of coronary artery movement is an independent predictor of the location of culprit lesions responsible for ST-segment elevation myocardial infarctions.

Methods for Three-Dimensional Geometric Characterization of the Arterial Vasculature

Complex vascular anatomy often affects endovascular procedural outcome. Accurate quantitative assessment of three-dimensional (3D) in-vivo arterial morphology is therefore vital for endovascular device design, and preoperative planning of percutaneous interventions. The aim of this work was to establish geometric parameters describing arterial branch origin, trajectory, and vessel curvature in 3D space that eliminate the errors implicit in planar measurements. 3D branching parameters at visceral and aortic bifurcation sites, as well as arterial tortuosity were determined from vessel centerlines derived from magnetic resonance angiography data for three subjects. Errors in coronal measurements of 3D branching angles for the right and left renal arteries were 3.1 +/- 3.4 degrees and 7.5 +/- 3.7 degrees , respectively. Distortion of the anterior visceral branching angles from sagittal measurements was less pronounced. Asymmetry in branching and planarity of the common iliac arteries was observed at aortic bifurcations. The renal arteries possessed considerably greater 3D curvature than the abdominal aorta and common iliac vessels with mean average values of 0.114 +/- 0.015 and 0.070 +/- 0.019 mm(-1) for the left and right, respectively. In conclusion, planar projections misrepresented branch trajectory, vessel length, and tortuosity proving the importance of 3D geometric characterization for possible applications in planning of endovascular interventional procedures and providing parameters for endovascular device design.

Vessel extraction in coronary X-ray Angiography

This paper describes a method to extract the vascular centerlines and contours in coronary angiography. The proposed approach associates geometric moments for the estimation of a "cylinder-like model" and relies on a tracking process. The orientation of the cylinder axis and its local diameter are computed from the analytical expressions of the geometric moments of up to order 2. Experimental results are presented on several images of two sequences that show the efficiency of the method.

Coronary x-ray angiographic reconstruction and image orientation

We have developed an interactive geometric method for 3D reconstruction of the coronary arteries using multiple single-plane angiographic views with arbitrary orientations. Epipolar planes and epipolar lines are employed to trace corresponding vessel segments on these views. These points are utilized to reconstruct 3D vessel centerlines. The accuracy of the reconstruction is assessed using: (1) near-intersection distances of the rays that connect x-ray sources with projected points, (2) distances between traced and projected centerlines. These same two measures enter into a fitness function for a genetic search algorithm (GA) employed to orient the angiographic image planes automatically in 3D avoiding local minima in the search for optimized parameters. Furthermore, the GA utilizes traced vessel shapes (as opposed to isolated anchor points) to assist the optimization process. Differences between two-view and multiview reconstructions are evaluated. Vessel radii are measured and used to render the coronary tree in 3D as a surface. Reconstruction fidelity is demonstrated via (1) virtual phantom, (2) real phantom, and (3) patient data sets, the latter two of which utilize the GA. These simulated and measured angiograms illustrate that the vessel center-lines are reconstructed in 3D with accuracy below 1 mm. The reconstruction method is thus accurate compared to typical vessel dimensions of 1-3 mm. The methods presented should enable a combined interpretation of the severity of coronary artery stenoses and the hemodynamic impact on myocardial perfusion in patients with coronary artery disease.

Reconstruction of coronary arteries from a single rotational X-ray projection sequence

Cardiovascular diseases remain the primary cause of death in developed countries. In most cases, exploration of possibly underlying coronary artery pathologies is performed using X-ray coronary angiography. Current clinical routine in coronary angiography is directly conducted in two-dimensional projection images from several static viewing angles. However, for diagnosis and treatment purposes, coronary artery reconstruction is highly suitable. The purpose of this study is to provide physicians with a three-dimensional (3-D) model of coronary arteries, e.g., for absolute 3-D measures for lesion assessment, instead of direct projective measures deduced from the images, which are highly dependent on the viewing angle. In this paper, we propose a novel method to reconstruct coronary arteries from one single rotational X-ray projection sequence. As a side result, we also obtain an estimation of the coronary artery motion. Our method consists of three main consecutive steps: 1) 3-D reconstruction of coronary artery centerlines, including respiratory motion compensation; 2) coronary artery four-dimensional motion computation; 3) 3-D tomographic reconstruction of coronary arteries, involving compensation for respiratory and cardiac motions. We present some experiments on clinical datasets, and the feasibility of a true 3-D Quantitative Coronary Analysis is demonstrated.

2D-3D registration of coronary angiograms for cardiac procedure planning and guidance

We present a completely automated 2D-3D registration technique that accurately maps a patient-specific heart model, created from preoperative images, to the patient's orientation in the operating room. This mapping is based on the registration of preoperatively acquired 3D vascular data with intraoperatively acquired angiograms. Registration using both single and dual-plane angiograms is explored using simulated but realistic datasets that were created from clinical images. Heart deformations and cardiac phase mismatches are taken into account in our validation using a digital 4D human heart model. In an ideal situation where the pre- and intraoperative images were acquired at identical time points within the cardiac cycle, the single-plane and the dual-plane registrations resulted in 3D root-mean-square (rms) errors of 1.60 +/- 0.21 and 0.53 +/- 0.08 mm, respectively. When a 10% timing offset was added between the pre- and the intraoperative acquisitions, the single-plane registration approach resulted in inaccurate registrations in the out-of-plane axis, whereas the dual-plane registration exhibited a 98% success rate with a 3D rms error of 1.33 +/- 0.28 mm. When all potential sources of error were included, namely, the anatomical background, timing offset, and typical errors in the vascular tree reconstruction, the dual-plane registration performed at 94% with an accuracy of 2.19 +/- 0.77 mm.

A quantitative analysis of 3-D coronary modeling from two or more projection images

A method is introduced to examine the geometrical accuracy of the three-dimensional (3-D) representation of coronary arteries from multiple (two and more) calibrated two-dimensional (2-D) angiographic projections. When involving more then two projections, (multiprojection modeling) a novel procedure is presented that consists of fully automated centerline and width determination in all available projections based on the information provided by the semi-automated centerline detection in two initial calibrated projections. The accuracy of the 3-D coronary modeling approach is determined by a quantitative examination of the 3-D centerline point position and the 3-D cross sectional area of the reconstructed objects. The measurements are based on the analysis of calibrated phantom and calibrated coronary 2-D projection data. From this analysis a confidence region (alpha degrees approximately equal to [35 degrees - 145 degrees]) for the angular distance of two initial projection images is determined for which the modeling procedure is sufficiently accurate for the applied system. Within this angular border range the centerline position error is less then 0.8 mm, in terms of the Euclidean distance to a predefined ground truth. When involving more projections using our new procedure, experiments show that when the initial pair of projection images has an angular distance in the range alpha degrees approximately equal to [35 degrees - 145 degrees], the centerlines in all other projections (gamma = 0 degrees - 180 degrees) were indicated very precisely without any additional centering procedure. When involving additional projection images in the modeling procedure a more realistic shape of the structure can be provided. In case of the concave segment, however, the involvement of multiple projections does not necessarily provide a more realistic shape of the reconstructed structure.