Validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections

The goal of the study was the validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections. Methods: The accuracy was tested in a complex phantom. In vivo, inter- and intraobserver agreement were assessed by analysis of routine angiograms. The sensitivity was evaluated using angiograms of patients having diagnostic vasoactive pharmacological intervention. Two-dimensional quantitative coronary angiography (2-D QCA) and 3-D QCA were compared concerning the accuracy of diameter evaluation. Results: 3-D QCA yields accurate results ( <3% error) even based on nonorthogonal views, provided that projections parallel to the object are avoided. The inter- and intraobserver variability is ≤ 5%. Significant (p < 0.01) changes of the volume (36–39%) and the diameter (19–21%) are detected following pharmacological intervention. 2-D QCA and 3-D QCA agree in short matched segments without foreshortening. 2-D QCA is rather sensitive to foreshortening and not suitable for evaluation of diameters of longer branches or total coronaries. Conclusion: 3-D QCA permits an accurate, reproducible and sensitive comprehensive three-dimensional geometric analysis of the coronaries and is superior to 2-D QCA with respect to extended diameter evaluation.     

The use of the minimum projection mode in 4-dimensional examination of the fetal heart with spatiotemporal image correlation.

OBJECTIVE: The minimum projection mode (MPM) is a rendering algorithm available in some 3- and 4-dimensional ultrasonography systems that, in 1 image, allows the visualization of vessels and cystic anatomic structures located in different scanning planes. The objective of this study was to compare the information displayed in images obtained with the MPM with their corresponding 2-dimensional ultrasonographic images from fetuses with and without structural heart defects. METHODS: Thirty-two volume data sets acquired with the spatiotemporal image correlation technique from fetuses with (n = 15) and without (n = 17) structural heart defects were analyzed. Rendered images of the upper abdomen, 4-chamber view, and 3-vessel view were compared with the corresponding 2-dimensional images. Two independent observers with experience in fetal echocardiography reviewed these volume data sets using the MPM. The visualization rate of specific anatomic structures seen from a transverse sweep of the heart was recorded for each observer, and the interobserver agreement was assessed by statistical indices of agreement (kappa statistic). RESULTS: Images obtained by the MPM displayed more vascular structures than those of corresponding 2-dimensional images at the level of the 3-vessel view. For conotruncal anomalies, the minimum mode projected the aorta and pulmonary arteries in 1 single plane, facilitating the understanding of their spatial relationships. The interobserver agreement score was moderate to "almost perfect" for assessment of most anatomic structures in the upper abdomen, 4-chamber view, and 3-vessel view sections. However, interobserver agreement ranged from fair to poor for visualization of the left outflow tract, atrial septum, and flap of the foramen ovale. CONCLUSIONS: The MPM is an alternative rendering modality that facilitates visualization of normal and abnormal vascular connections to the fetal heart at the level of the 3-vessel view. This technique may be useful in prenatal diagnosis of conotruncal anomalies and in assessment of the spatial relationships of abnormal vascular connections in the upper mediastinum.     

New approaches for the assessment of vessel sizes in quantitative (cardio-)vascular X-ray analysis

This paper presents new approaches for the assessment of the arterial and reference diameters in (cardio-)vascular X-ray images, designed to overcome the problems experienced in conventional quantitative coronary and vascular angiography approaches. In single or “straight” vessel segments, the arterial and reference diameter directions were made independent of each other in order to be able to measure the minimal lumen diameter (MLD) more accurately, especially in curved vessel segments. For ostial segments, an extension of this approach was used, to allow measurement of ostial lesions in sidebranches more proximal than using conventional methods. Furthermore, two new bifurcation approaches were developed. The validation study shows that the straight segment approach results in significant smaller MLDs (on average 0.032 mm) and the ostial approach achieves on average an increase in %DS of 3.8% and an increase in lesion length of 0.59 mm due to loosening the directional constraint. The validation of our new bifurcation approaches in phantom data as well as clinical data shows only small differences between pre- and post-intervention measurements of the reference diameters outside the bifurcation core (errors smaller than 0.06 mm) and the bifurcation core area (errors smaller than 1.4% for phantom data). In summary, these new approaches have led to further improvements in the quantitative analyses of (cardio-)vascular X-ray angiographies.     

Automatic online layer separation for vessel enhancement in X-ray angiograms for percutaneous coronary interventions

Percutaneous coronary intervention is a minimally invasive procedure that is usually performed under image guidance using X-ray angiograms in which coronary arteries are opacified with contrast agent. In X-ray images, 3D objects are projected on a 2D plane, generating semi-transparent layers that overlap each other. The overlapping of structures makes robust automatic information processing of the X-ray images, such as vessel extraction which is highly relevant to support smart image guidance, challenging. In this paper, we propose an automatic online layer separation approach that robustly separates interventional X-ray angiograms into three layers: a breathing layer, a quasi-static layer and a vessel layer that contains information of coronary arteries and medical instruments. The method uses morphological closing and an online robust PCA algorithm to separate the three layers. The proposed layer separation method ran fast and was demonstrated to significantly improve the vessel visibility in clinical X-ray images and showed better performance than other related online or prospective approaches. The potential of the proposed approach was demonstrated by enhancing contrast of vessels in X-ray images with low vessel contrast, which would facilitate the use of reduced amount of contrast agent to prevent contrast-induced side effects.     

Fusion of 3D QCA and IVUS/OCT

The combination/fusion of quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS)/optical coherence tomography (OCT) depends to a great extend on the co-registration of X-ray angiography (XA) and IVUS/OCT. In this work a new and robust three-dimensional (3D) segmentation and registration approach is presented and validated. The approach starts with standard QCA of the vessel of interest in the two angiographic views (either biplane or two monoplane views). Next, the vessel of interest is reconstructed in 3D and registered with the corresponding IVUS/OCT pullback series by a distance mapping algorithm. The accuracy of the registration was retrospectively evaluated on 12 silicone phantoms with coronary stents implanted, and on 24 patients who underwent both coronary angiography and IVUS examinations of the left anterior descending artery. Stent borders or sidebranches were used as markers for the validation. While the most proximal marker was set as the baseline position for the distance mapping algorithm, the subsequent markers were used to evaluate the registration error. The correlation between the registration error and the distance from the evaluated marker to the baseline position was analyzed. The XA-IVUS registration error for the 12 phantoms was 0.03 ± 0.32 mm (P = 0.75). One OCT pullback series was excluded from the phantom study, since it did not cover the distal stent border. The XA-OCT registration error for the remaining 11 phantoms was 0.05 ± 0.25 mm (P = 0.49). For the in vivo validation, two patients were excluded due to insufficient image quality for the analysis. In total 78 sidebranches were identified from the remaining 22 patients and the registration error was evaluated on 56 markers. The registration error was 0.03 ± 0.45 mm (P = 0.67). The error was not correlated to the distance between the evaluated marker and the baseline position (P = 0.73). In conclusion, the new XA-IVUS/OCT co-registration approach is a straightforward and reliable solution to combine X-ray angiography and IVUS/OCT imaging for the assessment of the extent of coronary artery disease. It provides the interventional cardiologist with detailed information about vessel size and plaque size at every position along the vessel of interest, making this a suitable tool during the actual intervention.     

Vesselness-based 2D–3D registration of the coronary arteries

Purpose  Robust and accurate automated co-registration of the coronary arteries in 3D CTA and 2D X-ray angiography during percutaneous coronary interventions (PCI), in order to present a fused visualization. Methods  A novel vesselness-based similarity measure was developed, that avoids an explicit segmentation of the X-ray image. A stochastic optimizer searches the optimal registration using the similarity measure. Results  Both simulated data and clinical data were used to investigate the accuracy and capture range of the proposed method. The experiments show that the proposed method outperforms the iterative closest point method in terms of accuracy (average residual error of 0.42 mm vs. 1.44 mm) and capture range (average 71.1 mm/20.3° vs. 14.1 mm/5.2°). Conclusion  The proposed method has proven to be accurate and the capture range is ample for usage in PCI. Especially the absence of an explicit segmentation of the interventionally acquired X-ray images considerably aids the robustness of the method.     

Fully automatic three-dimensional visualization of intravascular optical coherence tomography images: methods and feasibility in vivo

Intravascular optical coherence tomography (IV-OCT) is an imaging modality that can be used for the assessment of intracoronary stents. Recent publications pointed to the fact that 3D visualizations have potential advantages compared to conventional 2D representations. However, 3D imaging still requires a time consuming manual procedure not suitable for on-line application during coronary interventions. We propose an algorithm for a rapid and fully automatic 3D visualization of IV-OCT pullbacks. IV-OCT images are first processed for the segmentation of the different structures. This also allows for automatic pullback calibration. Then, according to the segmentation results, different structures are depicted with different colors to visualize the vessel wall, the stent and the guide-wire in details. Final 3D rendering results are obtained through the use of a commercial 3D DICOM viewer. Manual analysis was used as ground-truth for the validation of the segmentation algorithms. A correlation value of 0.99 and good limits of agreement (Bland Altman statistics) were found over 250 images randomly extracted from 25 in vivo pullbacks. Moreover, 3D rendering was compared to angiography, pictures of deployed stents made available by the manufacturers and to conventional 2D imaging corroborating visualization results. Computational time for the visualization of an entire data sets resulted to be ~74 sec. The proposed method allows for the on-line use of 3D IV-OCT during percutaneous coronary interventions, potentially allowing treatments optimization.OCIS codes: (170.4500) Optical coherence tomography, (100.6890) Three-dimensional image processing, (330.5000) Vision - patterns and recognition     

Fusion of three-dimensional X-ray angiography and three-dimensional echocardiography

Objective Cardiovascular intervention guidance requires knowledge of heart function relative to its blood supply or venous drainage. Functional and vascular anatomic data are usually generated on different imaging systems, so fusion of the data is necessary to simultaneously visualize the results for intervention planning and guidance. The objective of this work is to establish the feasibility of fusing volumetric ultrasound (U/S) data with three-dimensional (3D) X-ray imaging data for visualization of cardiac morphology, function and coronary venous drainage. Methods Temporally resolved U/S volume data was registered with the 3D reconstruction of vascular structures derived from X-ray modeling and reconstruction. U/S image registration was obtained by optical tracking fiducial markers with simultaneous X-ray imaging. The proposed technique was applied to phantom data for accuracy assessment of the registration process and to biventricular pacemaker implantation as clinical example. Results Fusion of U/S data with 3D X-ray reconstruction data produced an RMS registration error below 2 mm. Conclusion Preliminary clinical feasibility of U/S-derived data synchronously with X-ray derived 3D coronary venography was established. This technique can be applied for fusion of functional U/S data with 3D anatomic X-ray data of the coronary veins during a biventricular pacemaker implantation procedures.     

A quantitative evaluation of the three dimensional reconstruction of patients' coronary arteries

Background: Through extensive training and experience angiographers learn to mentally reconstruct the three dimensional (3D) relationships of the coronary arterial branches. Graphic computer technology can assist angiographers to more quickly visualize the coronary 3D structure from limited initial views and then help to determine additional helpful views by predicting subsequent angiograms before they are obtained. Methods: A new computer method for facilitating 3D reconstruction and visualization of human coronary arteries was evaluated by reconstructing biplane left coronary angiograms from 30 patients. The accuracy of the reconstruction was assessed in two ways: 1) by comparing the vessel's centerlines of the actual angiograms with the centerlines of a 2D projection of the 3D model projected into the exact angle of the actual angiogram; and 2) by comparing two 3D models generated by different simultaneous pairs on angiograms. The inter- and intraobserver variability of reconstruction were evaluated by mathematically comparing the 3D model centerlines of repeated reconstructions. Results: The average absolute corrected displacement of 14,662 vessel centerline points in 2D from 30 patients was 1.64 ± 2.26 mm. The average corrected absolute displacement of 3D models generated from different biplane pairs was 7.08 ± 3.21 mm. The intraobserver variability of absolute 3D corrected displacement was 5.22 ± 3.39 mm. The interobserver variability was 6.6 ± 3.1 mm. Conclusions: The centerline analyses show that the reconstruction algorithm is mathematically accurate and reproducible. The figures presented in this report put these measurement errors into clinical perspective showing that they yield an accurate representation of the clinically relevant information seen on the actual angiograms. These data show that this technique can be clinically useful by accurately displaying in three dimensions the complex relationships of the branches of the coronary arterial tree.     

Color-encoded distance visualization of cranial nerve-vessel contacts

Purpose  

Visualization of pathological contact between cranial nerves and vascular structures at the surface of the brainstem is important for diagnosis and treatment of neurovascular compression (NVC) syndromes. We developed a method for improved visualization of this abnormality.     

Real-time ultrasound-guided percutaneous dilatational tracheostomy: a feasibility study

Introduction  

Ultrasound (US) performed prior to percutaneous tracheostomy (PT) may be useful in avoiding injury to pretracheal vascular structures and in avoiding high placement of the tube. Bedside real-time US guidance with visualization of needle path is routinely utilized for other procedures such as central venous catheterization, and may enhance the safety and accuracy of PT without causing airway occlusion or hypercarbia. Our objective was to demonstrate that PT performed under real-time US guidance with visualization of needle path during tracheal puncture is feasible, including in patients with features that increase the technical difficulty of PT.     

Interventional 4D motion estimation and reconstruction of cardiac vasculature without motion periodicity assumption

Anatomical and functional information of cardiac vasculature is a key component in the field of interventional cardiology. With the technology of C-arm CT it is possible to reconstruct static intraprocedural 3D images from angiographic projection data. Current approaches attempt to add the temporal dimension (4D). In the assumption of periodic heart motion, ECG-gating techniques can be used. However, arrhythmic heart signals and slight breathing motion are degrading image quality frequently.To overcome those problems, we present a reconstruction method based on a 4D time-continuous B-spline motion field. The temporal component of the motion field is parameterized by the acquisition time and does not assume a periodic heart motion. The analytic dynamic FDK-reconstruction formula is used directly for the motion estimation and image reconstruction.In a physical phantom experiment two vessels of size 3.1 mm and 2.3 mm were reconstructed using the proposed method and an algorithm with periodicity assumption. For a periodic motion both methods obtained an error of 0.1 mm. For a non-periodic motion the proposed method was superior, obtaining an error of 0.3 mm/0.2 mm in comparison to 1.2 mm/1.0 mm for the algorithm with periodicity assumption. For a clinical test case of a left coronary artery it could be further shown that the method is capable to produce diameter measurements with an absolute error of 0.1 mm compared to state-of-the-art measurement tools from orthogonal coronary angiography. Further, it is shown for three different clinical cases (left/right coronary artery, coronary sinus) that the proposed method is able to handle a large variability of vascular structures and motion patterns. The complete algorithm is hardware-accelerated using the GPU requiring a computation time of less than 3 min for typical clinical scenarios.     

Assessment of obstruction length and optimal viewing angle from biplane X-ray angiograms

Three-dimensional quantitative coronary angiography (3D QCA) has been encouraged by the increasing need to better assess vessel dimensions and geometry for interventional purposes. A novel 3D QCA system based on biplane X-ray angiograms is presented in this paper. By correcting for the isocenter offset and by improving the epipolar constraint for corresponding two angiographic projections, accurate and robust reconstruction of the vessel centerline is achieved and the reproducibility of its applications, e.g., the assessments of obstruction length and optimal viewing angle, is guaranteed. The accuracy and variability in assessing the obstruction length and optimal bifurcation viewing angle were investigated by using phantom experiments. The segment length assessed by 3D QCA correlated well with the true wire segment length (r ² = 0.999) and the accuracy and precision were 0.04 ± 0.25 mm (P < 0.01). 3D QCA slightly underestimated the rotation angle (difference: −1.5° ± 3.6°, P < 0.01), while no significant difference was observed for the angulation angle (difference: −0.2° ± 2.4°, P = 0.54). In conclusion, the new 3D QCA approach allows highly accurate and precise assessments of obstruction length and optimal viewing angle from X-ray angiography.     

基于GA与模糊连接的冠状动脉造影图像分割

目的 针对模糊连接图像分割方法在实现上的困难,提出了一种基于遗传算法的模糊连接分割方法.方法 首先把路径强度作为遗传算法的寻优条件,从而得到图像中各点到种子点间的最优路径,其强度即该点的模糊连接度.然后,以各点的模糊连接度作为其灰度值,形成目标和背景不交叉的新图,最后用阈值法把目标物体提取出来.结果 实验结果表明,将该方法应用于冠状动脉造影图像的血管分割,能准确快速地将血管从背景中分割出来.结论 该分割方法较好地满足了临床冠心病诊断的要求.     

冠状动脉造影图像中血管的分割和量化分析

目的提出一种针对X线冠状动脉血管造影图像的处理和分析系统。方法以基于多尺度Hessian矩阵的血管增强图像为基础,采用数学形态学和Canny算子相结合的方法来实现血管骨架和边缘的自动提取。提出一种基于分段测量和血管平行特性的血管直径测量新方法,以实现对于血管直径的精确测量和血管狭窄长度以及狭窄程度等重要参数的量化描述。结果相比于全局测量,血管分段测量提高了血管直径的测量精度和速度;各段血管直径和狭窄程度的测量结果与多名临床医师的测量结果基本一致。结论本文提出的方法具有良好的有效性和实用性,有助于冠心病的诊断和治疗。     

Modeling the 3D coronary tree for labeling purposes

Coronary artery diseases are usually revealed using X-ray angiographies. Such images are complex to analyze because they provide a 2D projection of a 3D object. Medical diagnosis suffers from inter- and intra-clinician variability. Therefore, reliable software for the 3D reconstruction and labeling of the coronary tree is strongly desired. It requires the matching of the vessels in the different available angiograms, and an approach which identifies the arteries by their anatomical names is a way to solve this difficult problem. This paper focuses on the automatic labeling of the left coronary tree in X-ray angiography. Our approach is based on a 3D topological model, built from the 3D anthropomorphic phantom, Coronix. The phantom is projected under different angles of view to provide a data base of 2D topological models. On the other hand, the vessel skeleton is extracted from the patient's angiogram. The algorithm compares the skeleton with the 2D topological model which has the most similar vascular net shape. The method performs in a hierarchical manner, first labeling the main artery, then the sub-branches. It handles inter-individual anatomical variations, segmentation errors and image ambiguities. We tested the method on standard angiograms of Coronix and on clinical examinations of nine patients. We demonstrated successful scores of 90% correct labeling for the main arteries and 60% for the sub-branches. The method appears to be particularly efficient for the arteries in focus. It is therefore a very promising tool for the automatic 3D reconstruction of the coronary tree from monoplane temporal angiographic clinical sequences.     

Reproducibility of Shin’s method for necrotic core and calcium content in atherosclerotic coronary lesions treated with bioresorbable everolimus-eluting vascular scaffolds using volumetric intravascular ultrasound radiofrequency-based analysis

Although Virtual Histology intravascular ultrasound (VH-IVUS) is increasingly used in clinical research, the reproducibility of plaque composition remains unexplored in significant coronary artery and stented lesions. The purpose of this study was to assess the reproducibility of necrotic core and calcium content in atherosclerotic coronary lesions that were treated with a bioresorbable everolimus-eluting vascular scaffold (BVS) using a new measurement method (Shin’s method) by VH-IVUS. Eight patients treated with a BVS (Abbott Vascular, Santa Clara, CA, USA) were analyzed with serial VH-IVUS assessments, i.e., pre- and post-stenting, and at 6 months and 2 years follow-up. A total of 32 coronary segments were imaged to evaluate the reproducibility of volumetric VH-IVUS measurements. In Shin’s method, contours are drawn around the IVUS catheter (instead of the lumen) and vessel. Overall, in the imaged coronary segment, for necrotic core and dense calcium volumes, the relative intra-observer differences were 0.30 ± 0.22, 0.19 ± 0.16% for observer 1 and 0.45 ± 0.41, 0.36 ± 0.47% for observer 2, respectively. The inter-observer relative differences of necrotic core and dense calcium volumes were 0.51 ± 0.79 and 0.56 ± 1.01%, respectively. The present study demonstrates a good reproducibility for both, intra-observer and inter-observer measurements using Shin’s method. This method is suitable for the measurement of necrotic core and dense calcium using VH-IVUS in longitudinal studies, especially studies on bioresorbable scaffolds, because the degradation process will be fully captured independently of the location of the struts and their greyscale appearance.     

冠状动脉三维重建前期工作的关键技术研究

本文对利用冠状动脉血管造影图进行三维重建的前期工作进行了比较详细的介绍。主要包含:二维图像的预处理;血管的分割;血管骨架的提取;冠状动脉血管树特征点的识别以及血管段的匹配。     

Measurement of cerebral blood volume in mouse brain regions using micro-computed tomography

Micro-computed tomography (micro-CT) is an X-ray imaging technique that can produce detailed 3D images of cerebral vasculature. This paper describes the development of a novel method for using micro-CT to measure cerebral blood volume (CBV) in the mouse brain. As an application of the methodology, we test the hypotheses that differences in CBV exist over anatomical brain regions and that high energy demanding primary sensory regions of the cortex have locally elevated CBV, which may reflect a vascular specialization. CBV was measured as the percentage of tissue space occupied by a radio-opaque silicon rubber that fills the vasculature. To ensure accuracy of the CBV measurements, several innovative refinements were made to standard micro-CT specimen preparation and analysis procedures. Key features of the described method are vascular perfusion under controlled pressure, registration of the micro-CT images to an MRI anatomical brain atlas and re-scaling of micro-CT intensities to CBV units with selectable exclusion of major vessels. Histological validation of the vascular perfusion showed that the average percentage of vessels filled was 93 ± 3%. Comparison of thirteen brain regions in nine mice revealed significant differences in CBV between regions (p  < 0.0001) while cortical maps showed that primary visual and auditory areas have higher CBV than primary somatosensory areas.     

Novel diagnostic catheter specifically designed for both coronary arteries via the right transradial approach

The aim of this study was to assess the feasibility, safety, and performance of a novel diagnostic catheter specifically designed for engaging both coronary arteries via the right transradial artery approach. A total of 160 patients were randomized between the standard Judkins (5F R4, L4; Cordis Corporation, Miami, FL) and the 5F Tiger II (Terumo Corporation, Tokyo, Japan) catheters. End points included the duration of various procedures and the assessments of angiographic image quality and catheter performance. The Tiger II was associated with a significantly shorter (40%) total procedure time (199.6±50.2 vs. 331.5±72.9 s, p=0.001) and a 33% shorter total fluoroscopic time (93.1±33.8 vs. 138.2±47.6 s, p=0.001) for diagnostic coronary angiography, compared with those with the Judkins catheter. There was no significant difference between the Tiger II and Judkins catheters for left coronary angiographic quality (left anterior descending, 2.82±0.48 vs. 2.94±0.29, p=0.084; left circumflex, 2.90±0.38 vs. 2.87±0.44, p=0.629). The Tiger II provided superior right coronary angiograms, compared with the Judkins catheter (2.99± 0.11 vs. 2.82±0.48, p=0.003). For the left coronary angiograms, the initial randomized catheter completed the procedure in 91% of the patients with the Tiger II and in 98% with the Judkins (p=0.167) catheters. For the right coronary angiograms, 100% were completed with the Tiger II and 95% with the Judkins (p=0.120) catheters. There were no angiographic or clinical complications in either group, so the procedural success rate was 100%. The potential of the Tiger II catheter for use as a multipurpose catheter for right transradial coronary angiography to reduce procedural and X-ray times to the level of classic transfemoral coronary angiography has to be confirmed in a randomized study.