Evaluation of center-line extraction algorithms in quantitative coronary angiography

Objective testing of centerline extraction accuracy in quantitative coronary angiography (QCA) algorithms is a very difficult task. Standard tools for this task are not yet available. We present a simulation tool that generates synthetic angiographic images of a single coronary artery with predetermined centerline and diameter function. This simulation tool was used creating a library of images for the objective comparison and evaluation of QCA algorithms. This technique also provides the means for understanding the relationship between the algorithms' performance and limitations and the vessel's geometrical parameters. In this paper, two algorithms are evaluated and the results are presented.     

Three-dimensional digital subtraction angiography

A dye-edge tracking algorithm was used to determine the corresponding points in the two images (anterior-posterior and lateral) of the digital subtraction biplane angiography. This correspondence was used to reconstruct three-dimensional images of cerebral arteries in a dog experiment and a clinical observation. The method was tested by comparing the measured image of oblique view to the computed reconstructed image. For the present study, we have developed three new algorithms. The first algorithm is to determine the corresponding dye-edge points using the fact that the density of contrast media at the moving edge shows the same changing pattern in the two projection views. This moving pattern of dye-edge density is computed using a matching method of cross correlation for the two sequential frames' dye density. The second algorithm is for simplified perspective transformation, and the third is to identify the corresponding points using a complementary method for locating the approximate points on the small vessels. The present method can be applied to compute the velocity of blood flow using the dye-edge displacement and the three-dimensional distance data.     

High precision quantitative angiography

Statistical considerations on the precision in the determination of blood vessel dimensions from digitized cine angiographic images are described. The resolution requirements related to "point measurements" and segmental diameter curve evaluations are discussed. The error associated with inaccurate determination of the vessel's centerline is analyzed. The concepts have been implemented on a high-speed image analyzing system, which measures blood vessel diameters with advanced automation. The performance of the system was evaluated with blood vessel phantoms, ranging in diameter from 0.88 to 6.26 mm. For these phantoms the minimum measurable change in vessel dimension over 20-pixel (-1.1 mm) long segments ranged from 3.4 to 0.2 percent, respectively.     

CT冠状动脉造影与单纯冠状血管造影术的回顾性研究

目的探讨CT冠状动脉造影替代单纯常规冠状血管造影术的可行性。方法选取2007年6月16日-2008年6月17日在我院心内科行单纯CCA并最大狭窄处≤50%的患者共568例,其中1个月内曾在我院行CTCA检查的患者102人,对比CTCA与CCA的结果。结果80例为单纯CCA检查,19例为支架植入术后复查,3例为冠脉旁路移植术后复查;CTCA诊断8例偏差,诊断符合率为92.2%;其中19例支架植入术后复查患者,CTCA诊断3例偏差,诊断符合率为84.2%。结论CTCA可较准确的鉴别无需再血管化治疗的患者,包括支架植入术后复查的患者。     

Three-dimensional linear prediction and its application to digital angiography

In this article, we apply three-dimensional (3-D) linear least-squares (LS) prediction technique to the processing of digital subtraction angiography (DSA) image sequences. The main goal of this processing is the cancellation of motion artifacts, which is a visual structured noise that appears in current DSA images. We address two important issues with this new technique: first the misregistration between the mask and the contrast image and, second, the temporal filtering of DSA image sequence. Instead of treating these two issues separately, as conventional DSA methods do, we combine them into a 3-D LS prediction problem. Based on this approach, we develop a new efficient algorithm for the solution of normal equations. The algorithm is based on a new property of T ⁿ (Toeplitz to then) matrices that we prove. In order to match the image sequence physical characteristics, we further optimize practical parameters of this algorithm. Actual patient data is used for the evaluation of this new technique. Results show a significant improvement over the existing methods.     

Quantitative coronary angiography with deformable spline models

Although current edge-following schemes can be very efficient in determining coronary boundaries, they may fail when the feature to be followed is disconnected (and the scheme is unable to bridge the discontinuity) or branch points exist where the best path to follow is indeterminate. Here, the authors present new deformable spline algorithms for determining vessel boundaries, and enhancing their centerline features. A bank of even and odd S-Gabor filter pairs of different orientations are convolved with vascular images in order to create an external snake energy field. Each fitter pair will give maximum response to the segment of vessel having the same orientation as the filters. The resulting responses across filters of different orientations are combined to create an external energy field for snake optimization. Vessels are represented by B-Spline snakes, and are optimized on filter outputs with dynamic programming. The points of minimal constriction and the percent-diameter stenosis are determined from a computed vessel centerline. The system has been statistically validated using fixed stenosis and flexible-tube phantoms. It has also been validated on 20 coronary lesions with two independent operators, and has been tested for interoperator and intraoperator variability and reproducibility. The system has been found to be specially robust in complex images involving vessel branchings and incomplete contrast filling     

多层螺旋CT血管造影中的冠脉运动估计

提出了由多层螺旋计算机层析(MSCT)数据估计冠脉三维运动的算法。首先对多期相数据进行基于Hessian矩阵的局部血管增强,随后采用自适应阈值区域生长方法分割出血管并进行细化,得到不同时刻的冠脉骨架。血管进行分段后,利用连贯点漂移(CPD)点配准算法对不同期相的各段血管配准,计算点对之间的对应关系矩阵及空间变换,从而估计三维运动场。采用运动场已知的模拟数据评估算法精度,结果表明,对超过50mm的大幅度运动,配准误差小于1voxel,运动场估计误差小于1%。对实际的全期相数据,估计左右冠脉的运动场,也获得了较为均匀和平滑的结果。     

Three-dimensional motion tracking of coronary arteries in biplane cineangiograms

A three-dimensional (3-D) method for tracking the coronary arteries through a temporal sequence of biplane X-ray angiography images is presented. A 3-D centerline model of the coronary vasculature is reconstructed from a biplane image pair at one time frame, and its motion is tracked using a coarse-to-fine hierarchy of motion models. Three-dimensional constraints on the length of the arteries and on the spatial regularity of the motion field are used to overcome limitations of classical two-dimensional vessel tracking methods, such as tracking vessels through projective occlusions. This algorithm was clinically validated in five patients by tracking the motion of the left coronary tree over one cardiac cycle. The root mean square reprojection errors were found to be submillimeter in 93% (54/58) of the image pairs. The performance of the tracking algorithm was quantified in three dimensions using a deforming vascular phantom. RMS 3-D distance errors were computed between centerline models tracked in the X-ray images and gold-standard centerline models of the phantom generated from a gated 3-D magnetic resonance image acquisition. The mean error was 0.69 (+/- 0.06) mm over eight temporal phases and four different biplane orientations.     

护理干预在640层螺旋CT冠状动脉血管成像中的应用

目的:探讨护理干预在640层螺旋CT冠状动脉血管成像中的价值.方法:回顾分析300例行640层螺旋CT冠状动脉血管成像患者:在检查前进行正确呼吸护理干预、准确的静脉穿刺;对因紧张、恐惧等因素导致不同程度心率增快含服倍他乐克25至50 mg使心率降至≤75次/分钟,对呼吸节律异常进行适当的心理干预;检查完成后观察30分钟有无对比剂不良反应.结果:1例不能配合屏气,图像达不到诊断要求;1例对比剂渗漏,冠状动脉不显影;其余病例都成功完成检查.结论在螺旋CT冠状动脉血管成像检查中护理干预起到关键的作用,正确的呼吸配合、准确的静脉穿刺、适当的心率护理干预和恰当的心理护理干预关系到整个检查能否成功,心率护理干预还可以减少患者接受的X线辐射剂量.     

CT冠状动脉造影结合负荷心肌灌注显像诊断冠心病的研究进展

CT冠状动脉造影结合负荷心肌灌注显像从解剖学及血流动力学两个方面为冠心病的无创诊断提供了全面、准确的信息。两者融合图像是近年研究的热点,本文对此领域的研究进行综述。     

3例急性冠脉综合征患者CTA、冠脉造影及OCT对比

目的了解急性冠脉综合征患者冠脉CTA、冠脉造影、OCT的表现。方法急性冠脉综合征患者3例,在行冠脉造影前均行64排CT(Somatom Definition)冠脉CTA检查,明确罪犯病变;常规冠状动脉造影后行OCT检查(Lightlab),分别分析冠脉CT、冠脉造影和OCT影像学结果。结果冠脉CTA均提示为软斑块,斑块最低CT值均小于100Hu,1例伴有轻度钙化,斑块负荷较重,均呈正性重构;OCT示2例有极薄的纤维帽(分别为50μm和40μm),纤维帽后有大的脂核。结论冠脉CTA对于血管壁较宏观的观察较有优势,冠脉造影可以动态观察血管的情况,OCT可细致观察血管壁、斑块和血栓。     

基于形态学和分水岭算法的冠状动脉造影图像分割研究

图像分割技术是图像处理领域非常活跃的研究课题,但目前还不完善,尤其对狭长区域的分割还没有给出较好的分割算法,如血管图像的分割等。将分水岭算法与数学形态学算法结合起来应用于冠状动脉造影中,并用来进行冠状动脉造影图像血管分割,取得了较好的分割结果。详细论述了数学形态学算法的原理,通过形态学知识提取图像边界。利用图像的几何特征,去除非目标区域,再采用分水岭变换进行图像分割,并利用冠状动脉造影图像验证了该方法的优势。通过实验验证了其可行性与优越性。     

ECG电流调制技术在冠状动脉CTA中的应用价值

目的：评价心电图（electrocardiograph,ECG）电流调制技术在冠状动脉CTA中的应用价值。方法：84例行冠状动脉CT血管造影（CT Angiography,CTA）检查的患者随机分为A、B两组,每组42例,A组采用传统方式扫描,B组采用ECG电流调制技术。对两种扫描所得图像的质量、噪声、CT剂量指数（CT dose index,CTDl）有效剂量（effective dose ED）进行统计学分析。结果：两组图像质量评分及噪声评分分别为：A组（3.58±0.22）分和（23.13±3.45）分,B组（3.56±0.25）分和（23.27±3.32）分,两组间差异不明显（P〉0.05）。A组CTDI和ED分别为：（93.03±4.32）mGy和（35.53±2.01）mSv,B组为（58.36±3.24）mGy和（20.00±2.77）mSv,B组的辐射剂量较A组明显降低（P〈0.01）。结论：在不明显影响图像质量的情况下,ECG电流调制技术能有效降低冠状动脉CTA辐射剂量,可以作为冠状动脉CTA的常规辅助技术。     

Evaluation of iterative sparse object reconstruction from few projections for 3-D rotational coronary angiography

A 3-D reconstruction of the coronary arteries offers great advantages in the diagnosis and treatment of cardiovascular disease, compared to 2-D X-ray angiograms. Besides improved roadmapping, quantitative vessel analysis is possible. Due to the heart's motion, rotational coronary angiography typically provides only 5–10 projections for the reconstruction of each cardiac phase, which leads to a strongly undersampled reconstruction problem. Such an ill-posed problem can be approached with regularized iterative methods. The coronary arteries cover only a small fraction of the reconstruction volume. Therefore, the minimization of the ${mbi L}_1$ norm of the reconstructed image, favoring spatially sparse images, is a suitable regularization. Additional problems are overlaid background structures and projection truncation, which can be alleviated by background reduction using a morphological top-hat filter. This paper quantitatively evaluates image reconstruction based on these ideas on software phantom data, in terms of reconstructed absorption coefficients and vessel radii. Results for different algorithms and different input data sets are compared. First results for electrocardiogram-gated reconstruction from clinical catheter-based rotational X-ray coronary angiography are presented. Excellent 3-D image quality can be achieved.      

Assessment of diffuse coronary artery disease by quantitative analysis of coronary morphology based upon 3-D reconstruction from biplane angiograms

Quantitative evaluations on coronary vessel systems are of increasing importance in cardiovascular diagnosis, therapy planning, and surgical verification. Whereas local evaluations, such as stenosis analysis, are already available with sufficient accuracy, global evaluations of vessel segments or vessel subsystems are not yet common. Especially for the diagnosis of diffuse coronary artery diseases, the authors combined a 3D reconstruction system operating on biplane angiograms with a length/volume calculation. The 3D reconstruction results in a 3D model of the coronary vessel system, consisting of the vessel skeleton and a discrete number of contours. To obtain an utmost accurate model, the authors focussed on exact geometry determination. Several algorithms for calculating missing geometric parameters and correcting remaining geometry errors were implemented and verified. The length/volume evaluation can be performed either on single vessel segments, on a set of segments, or on subtrees. A volume model based on generalized elliptical conic sections is created for the selected segments. Volumes and lengths (measured along the vessel course) of those elements are summed up. In this way, the morphological parameters of a vessel subsystem can be set in relation to the parameters of the proximal segment supplying it. These relations allow objective assessments of diffuse coronary artery diseases.     

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.     

Three-dimensional displays

Three-dimensional display techniques can be classified as binocular and autostereoscopic types, still and animated types, nontransmitted and transmitted types, and nonholographic and holographic types. This paper deals mainly with autostereoscopic still nontransmitted techniques. Holographic and nonholographic tecniques are described on about equal footing. For the sake of brevity, emphasis is placed upon those techniques that appeared in the past several years. However, some old techniques of historical and/or practical importance are also mentioned because rather few textbooks are available in this field. In the final part, state of the art of three-dimensional display for animated and transmitted images (three-dimensional television) is described. Speculations on the direction of the development are presented.     

Model evaluation and calibration for prospective respiratory motion correction in coronary MR angiography based on 3-D image registration

Image processing was used as a fundamental tool to derive motion information from magnetic resonance (MR) images, which was fed back into prospective respiratory motion correction during subsequent data acquisition to improve image quality in coronary MR angiography (CMRA) scans. This reduces motion artifacts in the images and, in addition, enables the usage of a broader gating window than commonly used today to increase the scan efficiency. The aim of the study reported in this paper was to find a suitable motion model to be used for respiratory motion correction in cardiac imaging and to develop a calibration procedure to adapt the motion model to the individual patient. At first, the performance of three motion models [one-dimensional translation in feet-head (FH) direction, three-dimensional (3-D) translation, and 3-D affine transformation] was tested in a small volunteer study. An elastic image registration algorithm was applied to 3-D MR images of the coronary vessels obtained at different respiratory levels. A strong intersubject variability was observed. The 3-D translation and affine transformation model were found to be superior over the conventional FH translation model used today. Furthermore, a new approach is presented, which utilizes a fast model-based image registration to extract motion information from time series of low-resolution 3-D MR images, which reflects the respiratory motion of the heart. The registration is based on a selectable global 3-D motion model (translation, rigid, or affine transformation). All 3-D MR images were registered with respect to end expiration. The resulting time series of model parameters were analyzed in combination with additionally acquired motion information from a diaphragmatic MR pencil-beam navigator to calibrate the respiratory motion model. To demonstrate the potential of a calibrated motion model for prospective motion correction in coronary imaging, the approach was tested in CMRA examinations in five volunteers.     

基于CAD三维技术的室分系统三维化设计构想

传统的室分系统是基于CAD的2D技术设计的,但是现在的网络结构越来越复杂,针对传统的室分系统做前期分析非常困难且难以检验。CAD的三维技术能够更加具体的显示出建筑的构造,基于CAD三维技术设计的室分系统,更便于对室分系统的前期的分析。