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.     

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.     

Digital Flashing Tomosynthesis (DFTS) — A technique for three-dimensional coronary angiography

Digital Flashing Tomosynthesis (DFTS) represents a technique for three-dimensional (3D) coronary angiography. Four ECG-gated simultaneously flashed X-ray tubes generate a multiperspective digital substraction image as DFTS multiangiogram for 3D reconstruction and visualization. Computerized morphologic and morphometric quantitative analysis can be performed including videodensitometry. Postmortem coronary angiography of 30 human hearts with suspected coronary artery disease was performed by 35-mm cine technique and by DFTS. The results of angiographic measurements in 50 stenotic arterial segments were compared with the histologic reference and show excellent regression results with correlation coefficients of more than 0.95 (p?-0.0001). No significant differences in standard errors of estimates between the techniques were found. DFTS yields an accuracy in depiction of the coronary arteries and angiographic estimation of arterial lumen equivalent to 35-mm cineangiography. DFTS images can be directly used for visual interpretation and for computerized morphologic and morphometric quantitative analysis. DFTS technology reduces the amount of radiation exposure, the amount of contrast medium, and the time of the procedure. DFTS offers the possibility to obtain 3D images of the coronary artery tree.     

大范围主动脉夹层3.0 T两段式双期三维对比增强MR血管成像技术与临床价值

目的探讨大范围主动脉夹层(AD)3.0 T两段式双期3D CEMRA的扫描技术特点与诊断意义。材料与方法 14例大范围AD患者行循环时间(TT)测试和3D FLASH-turbo MRA序列3D CEMRA连续2期扫描。比较真、假腔在TT、峰值信号(SPE)和3D CEMRA信号方面的差异;观测AD双腔的双期显影、内膜破口及腹主动脉分支与双腔的关系,结果与主动脉DSA对照。结果 AD真、假腔TT分别为(13.4±4.8)s、(17.5±4.7)s(P0.01);峰值信号分别为108.7±28.4、83.5±39.3(P0.05)。真、假腔双期3D CEMRA信号分别为第一期:391.4±83.7、142.9±77.2(P0.01);第二期:225.0±66.1、231.6±80.0(P0.50)。双期3D CEMRA上AD双腔呈特征性动态显现:第一期,真腔全程显影,假腔节段性显影;第二期,真腔信号减退,假腔全程显影。检出内膜破口23个,数量、位置与DSA一致;8个呈血流喷射征。5条左肾动脉、3条右肾动脉和1条腹腔动脉干开口于假腔。结论基于AD双腔血流动力学差异的TT测试和双期扫描,是大范围AD 3.0 T两段式双期3D CEMRA的技术要点,该方法可满足大范围AD的诊断要求。     

Coronary angiography enhancement for visualization

High quality visualization on X-ray angiograms is of great significance both for the diagnosis of vessel abnormalities and for coronary interventions. Algorithms for improving the visualization of detailed vascular structures without significantly increasing image noise are currently demanded in the market. A new algorithm called stick-guided lateral inhibition (SGLI) is presented for increasing the visibility of coronary vascular structures. A validation study was set up to compare the SGLI algorithm with the conventional unsharp masking (UM) algorithm on 20 still frames of coronary angiographic images. Ten experienced QCA analysts and nine cardiologists from various centers participated in the validation. Sample scoring value (SSV) and observer agreement value (OAV) were defined to evaluate the validation result, in terms of enhancing performance and observer agreement, respectively. The mean of SSV was concluded to be 77.1 ± 11.9%, indicating that the SGLI algorithm performed significantly better than the UM algorithm (P-value < 0.001). The mean of the OAV was concluded to be 70.3%, indicating that the average agreement with respect to a senior cardiologist was 70.3%. In conclusion, this validation study clearly demonstrates the superiority of the SGLI algorithm in the visualization of coronary arteries from X-ray angiograms.     

Transesophageal examination of the left coronary artery with a 7.5 MHz annular array two-dimensional color flow Doppler transducer

To determine the value of a recently developed 7.5 MHz annular array two-dimensional and color flow Doppler transducer for examination of the proximal parts of the left coronary artery, 25 patients were studied immediately after coronary artery bypass surgery, and the findings were compared with preoperative coronary angiograms. With two-dimensional imaging, the left main coronary artery was visualized in 22 patients (88%), left anterior descending in 13 patients (52%), and circumflex in 22 patients (88%). Stenoses were correctly identified in four of four left main coronary arteries, in five of seven left anterior descending arteries, and in none of four left circumflex arteries. Adding color flow to two-dimensional imaging in 20 patients, we found a disturbed flow signal, as a sign of stenosis, in five of five left anterior descending artery and two of four left circumflex artery stenoses. We concluded that these initial findings with this new 7.5 MHz annular array two-dimensional and color flow Doppler transducer, are promising in imaging and detection of stenoses in the proximal parts of the left coronary artery.     

3D MR coronary angiography: optimization of the technique and preliminary results

Objective: Current clinical full MR angiography with multiple breathhold multiple thin slab acquisition (MTS) is difficult and arduous. This study describes the optimisation of the whole heart free – breathing balanced turbo field echo (B-TFE) protocol. A high-resolution image of the whole heart is produced in less or comparable time to MTS acquisition and allows for reconstruction afterwards to visualise the individual coronary arteries. The scan is easily performed because the volume has to be targeted only once.Design and setting: Eighteen healthy adults without a history of cardiovascular disease underwent free-breathing 3D MR angiography with the B-TFE protocol. The whole-heart data set was reformatted in identical orientations in all subjects to visualise the major coronary arteries.Main outcome measures: Vessel length, signal and contrast to noise ratio were determined and compared for each vessel.Results: Mean visible vessel lengths were 116 mm for the right, 102 mm for the left main and left descending and 76 mm for the left circumflex coronary artery. The average signal to noise ratio was 7.5 and contrast to noise ratio was 4.9. Because of the need for synchronised cardiac and respiratory triggering the coronaries could not be judged in 25% of the subjects.Conclusions: The optimised B-TFE protocol had equal judgeability and vessels could be judged over longer contiguous distances compared to earlier implementations of the B-TFE protocol. We conclude whole heart free breathing navigator-gated and slice-tracked 3D coronary MR angiography with use of the adjusted B-TFE protocol is possible, but still suboptimal for clinical use.     

Diffusion-prepared segmented steady-state free precession: Application to 3D black-blood cardiovascular magnetic resonance of the thoracic aorta and carotid artery walls.

This work developed a three-dimensional (3D) diffusion-prepared segmented steady-steady free precession (DP-SSFP) cardiovascular magnetic resonance (CMR) sequence for black-blood (BB) thoracic aortic and carotid wall visualization. In 14 healthy volunteers, BB CMR of the thoracic aorta (n = 7) and carotid arteries (n = 7) was performed over 12 cm and 3 cm of transversal coverage, respectively, with a single 3D DP-SSFP acquisition and multiple two-dimensional (2D) slices using a T2-weighted (T2W) double inversion-recovery fast spin-echo (DIR-FSE) sequence. Arterial wall area (WA), lumen area (LA), and wall-lumen contrast-to-noise ratio (CNR) measured from the 3D DP-SSFP images were compared to those measured from the 2D T2W DIR-FSE images. Strong agreement in WA and LA between the two techniques was observed in the thoracic aorta (WA: intraclass correlation coefficient (ICC) = 0.866, LA: ICC = 0.993; p < 0.001 for both) and carotid arteries (WA: ICC = 0.939, LA: ICC = 0.991; p < 0.001 for both). Adjusted for slice thickness and number of slices, higher effective CNR per unit time (i.e., CNR efficiency) was attained with 3D DP-SSFP than 2D T2W DIR-FSE during thoracic aortic wall imaging (11.6 +/- 1.4 vs. 2.9 +/- 0.5; p < 0.001) and carotid artery wall imaging (10.1 +/- 1.9 vs. 3.1 +/- 0.5; p < 0.001). Diffusion-prepared segmented SSFP is a promising vessel wall CMR sequence that allows for 3D acquisition of thin and contiguous slices with BB image contrast.     

Noninvasive test of nitrate-induced coronary vasomotion by 1.5-T whole-heart 3D magnetic resonance angiography using a T2-prepared SSFP sequence

This study was aimed to investigate the use of 1.5-T whole-heart 3D coronary MRA employing a T2-prepared SSFP sequence for assessing epicardial coronary artery vasodilation following exogenous nitrates. Navigator-gated whole-heart 3D coronary MRA was performed before and after sublingual nitroglycerin (NTG) in 22 volunteers and a T2-prepared SSFP sequence was used for imaging of coronary arteries without MR contrast agent. Coronary cross-sectional area was measured on pre- and post-NTG images of equivalent coronary segments in the major coronary arteries and whole-heart coronary vasodilation was analyzed quantitatively. Measurements were obtained by two independent investigators. Coronary vasodilation could be observed directly on multiplanar reformatted and three-dimensional volume-rendered MR images. On quantitative analysis, NTG administration results in the whole-heart coronary vasodilation by an average of 37.3?±?12.7%. There was moderate yet significant correlation between the NTG-induced vasodilation and age (r?=?-0.52, P?=?0.02). The mean absolute cross-sectional area of the coronary arteries was significantly higher after sublingual NTG in all the major coronary arteries. The coronary area measurements had an interobserver variability of 8?±?3% and an intraoberver variability of 4?±?2%. Non-contrast-enhanced 1.5-T SSFP whole-heart coronary MRA can noninvasively measure endothelium-independent coronary vasodilation over the entire heart with high feasibility and is a promising noninvasive method to explore whole-heart coronary smooth muscle cell function following exogenous nitrates in clinical practice.     

肥厚性心肌病的冠状动脉造影分析

目的：了解肥厚性心肌病患者冠状动脉及其特征。方法：25例肥厚性心肌病患者行冠状动脉造影,观察其冠状动脉分布及特点,测量其各分支中段内径,并与同期行冠状动脉造影的正常人相比。结果：肥厚性心肌病患者冠状动脉供血呈左优势者占20％,各亚型间无明显判别：5例发现合并冠心病,其中1例行PTCA及冠脉内支架术,另1例植入永久性DDD起搏器治疗,1例左前降支中段发现冠脉肌桥;无冠状协脉病变的19例患者左主干,回旋支及右冠脉中段内径较正常者明显粗大（P＜005）,结论：肥厚性心肌病患者冠脉供血呈左优势者比较较高,其冠状动脉内径较正常者粗大,疑有合并冠心病者须行冠状动脉造影,对指导治疗有一定意义。     

A study of in vitro and in vivo MR of free-breathing whole-heart 3D coronary angiography using parallel imaging

To evaluate parallel-imaging methods in free-breathing whole-heart 3D coronary magnetic resonance angiography and assess the navigator techniques and visualization rates of the major coronary arteries. We compared key parameters of the generalized autocalibrating partially parallel acquisition and modified sensitive encoding images in vitro phantom MRI; performed the MRA with GRAPPA parallel imaging in healthy volunteers; compared 1D- and 2D-prospective acquisition correction and analyzed the differences; and evaluated the visualization of major coronary arterial branches. GRAPPA images had higher signal-to-noise ratio and contrast-to-noise ratio and fewer aliasing artifacts. The coronary arteries were adequately visualized in 38 volunteers. 2D-PACE had a higher navigator efficiency, shorter scan time, and gave clearer reconstructed images in comparison with 1D-PACE. GRAPPA images were superior to mSENSE images. Whole-heart 3D coronary MRA along with parallel-imaging technique is a potential clinical method, and 2D-PACE is a better navigation technique than 1D-PACE.     

A study of in vitro and in vivo MR of free-breathing whole-heart 3D coronary angiography using parallel imaging

To evaluate parallel-imaging methods in free-breathing whole-heart 3D coronary magnetic resonance angiography and assess the navigator techniques and visualization rates of the major coronary arteries. We compared key parameters of the generalized autocalibrating partially parallel acquisition and modified sensitive encoding images in vitro phantom MRI; performed the MRA with GRAPPA parallel imaging in healthy volunteers; compared 1D- and 2D-prospective acquisition correction and analyzed the differences; and evaluated the visualization of major coronary arterial branches. GRAPPA images had higher signal-to-noise ratio and contrast-to-noise ratio and fewer aliasing artifacts. The coronary arteries were adequately visualized in 38 volunteers. 2D-PACE had a higher navigator efficiency, shorter scan time, and gave clearer reconstructed images in comparison with 1D-PACE. GRAPPA images were superior to mSENSE images. Whole-heart 3D coronary MRA along with parallel-imaging technique is a potential clinical method, and 2D-PACE is a better navigation technique than 1D-PACE.     

屏气法三维磁共振冠状动脉血管造影诊断先天性冠状动脉起源畸形

目的探讨屏气法三维磁共振冠状动脉造影(3D MRCA)显示畸形冠状动脉与主动脉根部、右心室流出道关系的可行性及价值.方法 5名临床拟诊患者、1例志愿者接受MRCA检查,以屏气法三维稳态进动快速成像(3D true-FISP)梯度回波序列采集图像,获得左、右冠状动脉图像,分析畸形冠状动脉近段与冠状动脉窦(Valsalva窦)、右心室流出道的位置关系.结果 6例MRCA均明确诊断先天性冠状动脉起源畸形,畸形血管近段均走行于主动脉根部与右心室流出道之间.结论屏气法3D MRCA可明确诊断先天性冠状动脉起源畸形,显示畸形冠状动脉近段的走行路经,是一种可行的影像诊断方法.     

Evaluation of Short-Axis and Long-Axis Myocardial Function with Two-Dimensional Strain Echocardiography in Patients with Different Degrees of Coronary Artery Stenosis

This study was designed to characterize the changes in the peak systolic longitudinal, circumferential and radial strains by using 2-D strain echocardiography in patients with coronary artery stenosis without segmental wall motion abnormalities on conventional 2-D echocardiography. 2D strain echocardiography was performed in 44 patients with different degrees of coronary artery stenosis. Myocardial longitudinal, circumferential and radial strain profiles were obtained and peak systolic strain values were measured. The peak systolic longitudinal strain was significantly reduced in myocardial segments subtended by coronary arteries with greater than 75% stenosis when compared with those subtended by coronary artery with less than 75% stenosis and those in control. Sensitivity and specificity were 74% and 72%, respectively, for peak systolic longitudinal strain to predict segments subtended by coronary arteries with greater than 75% stenosis (cutoff value −17.7%; area under the receiver operating characteristic curve, 0.825). There were no significant differences in circumferential and radial strains among myocardial segments subtended by coronary arteries with greater than 75% stenosis and those with less than 75% stenosis and in control. In conclusion, our study suggests that analysis of long-axis cardiac function by using the 2-D strain echocardiography may help to identify the myocardial segments subtended by coronary arteries with severe stenosis. (E-mail: youdeng@public.wh.hb.cn).     

组织谐波显像和CK技术结合在冠心病应用的研究

目的　彩色室壁运动技术（Ｃｏｌｏｒ Ｋｉｎｅｓｉｓ ＣＫ） 的应用受二维图像质量影响。组织谐波显像（ｔｉｓｓｕｅ ｈａｒｍｏｎｉｃｉｍａｇｅ ＴＨＩ）能改善声窗不佳者二维图像质量。本文拟观察ＴＨＩ对ＣＫ 评价室壁运动的影响。方法　非选择性冠心病患者２１ 名,分别在基波（ＦＩ） 和谐波（ＨＩ）下采集二维和收缩末ＣＫ 图像,比较两种显像方式下心内膜显示、二维和ＣＫ 图像质量以及ＣＫ 评价室壁运动的准确性。结果　ＨＩ下心内膜显示改善,二维和ＣＫ 图像质量提高,ＣＫ图像采集成功率由ＦＩ的８４－８ ％ 增加到９５－８ ％ ,评价室壁运动的准确性由６８－４ ％ 增加到８８－７％ 。结论　ＴＨＩ和ＣＫ技术的结合提高了ＣＫ 技术的临床适用性。     

Dipyridamole echocardiography in the detection of vulnerable myocardium in the early postinfarction period

To evaluate the effect of dipyridamole on regional wall motion after myocardial infarction two-dimensional echocardiograms were obtained on 21 postinfarction patients immediately before and 7 to 10 minutes after the intravenous infusion of ddipyridamole (0.60 mg/kg). All patients underwent coronary angiography, and 20 patients underwent scintigraphy with dipyridamole thallium immediately subsequent to dipyridamole echocardiography. Dipyridamole augmented noninfarct zone regional wall motion in 20 of 31 regions supplied by nonstenotic coronary arteries. In contrast, only one of eight regions of noninfarct zone myocardium supplied by coronary arteries with greater than a 70% luminal diameter narrowing (vulnerable myocardium) was able to augment the regional wall motion subsequent to dipyridamole administration (p = 0.05). Dipyridamole echocardiography appears to be a safe and sensitive technique that may be useful in the detection of vulnerable myocardium in the early postinfarction period.     

Optimization of ex vivo CT- and MR- Imaging of Atherosclerotic Vessel Wall Changes

OBJECTIVE: To optimize a methodology for ex vivo imaging of atherosclerotic vessel wall changes using multidetector-row computed tomography (MDCT) and multi-contrast magnetic resonance imaging (MRI). METHODS: In phantom studies and studies on intact ex vivo porcine and human hearts, various filling mixtures of MDCT and MRI contrast agents have been evaluated, to enable filling and distension of the coronary arteries for optimal visualization of atherosclerotic vessel wall changes with both techniques. Various proportions of methyl cellulose, iodine-containing CT contrast agent and paramagnetic MR contrast agent containing iron-oxide particles have been tested. Imaging parameters have been optimized for high resolution plaque imaging using a four detector-row CT scanner and a 1.5 T MR system. RESULTS: Phantom studies and studies on ex vivo porcine and human hearts demonstrated optimal proportion of methyl cellulose and CT contrast agent to be 98% vs. 2%, and 75% vs. 25% of methyl cellulose vs. MR contrast agent, respectively. These proportions provided optimal opacification of the vessel lumen in the MDCT images with 250 Hounsfield Units, and good signal suppression within the vessel lumen in the MR images, resembling in vivo imaging techniques. After retrospective matching with histopathology, atherosclerotic lesions of the human ex vivo specimens could be identified on MRI and MDCT images. CONCLUSION: Using an optimized mixture of methyl cellulose, MDCT and MRI contrast agents, visualization of atherosclerotic vessel wall changes is feasible, and applicable to various ex vivo models.     

Magnetic resonance imaging of coronary artery occlusions in the navigator technique

Non-invasive assessment of coronary arteries is possible with magnetic resonance imaging (MRI). Respiratory gated MR coronary angiography is a new imaging technique that permits reconstruction of the coronary arteries based on a three-dimensional (3D) data set obtained from the free-breathing patient. In this study, respiratory gated MR angiography (MRA) was performed to assess coronary artery occlusions. MRI was performed in 25 patients who had been referred for conventional coronary angiography because of suspected coronary artery disease. Coronary artery occlusion was evaluated in the proximal and middle vessel segments after multiplanar coronary reconstruction of the MR images. Five patients were excluded from the study; in the remaining 20 patients 120 coronary artery segments were analyzed. Good image quality could be obtained for 85% of the segments. Eighteen of the 24 occlusions were confirmed by MRI, the overall sensitivity was 75% and the specificity was 100%. The best results were found in the proximal left anterior descending (LAD) and descending parts of the right coronary artery (RCA), where all occlusions were confirmed. These results showed that coronary artery occlusions can be detected in the proximal and middle LAD and RCA using 3D respiratory gated MRA. Further technical improvements, especially in spatial resolution, are necessary before MRA can become a reliable diagnostic tool in the non-invasive evaluation of coronary arteries.     

Visualization of coronary arteries using intravenous contrast agent and real-time 3-dimensional echocardiography in a patient with hypertrophic cardiomyopathy.

Real-time 3-dimensional echocardiography is a recently developed imaging technique that provides unique information on spatial geometry in real time. We described an asymptomatic patient with hypertrophic obstructive cardiomyopathy for whom 3-dimensional echocardiography was performed after intravenous injection of perfluorocarbon-filled microbubbles. It resulted in enhancement of the left ventricular endocardial border delineation and myocardial perfusion in the hypertrophic septum. A clear visualization of the entire course of the left anterior descending coronary artery and its septal perforator branches was obtained. This case illustrates the potential of real-time 3-dimensional echocardiography to improve the anatomic evaluation of coronary arteries, especially when combined with contrast agents.     

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.