Automated selection of major arteries and veins for measurement of arteriolar-to-venular diameter ratio on retinal fundus images

An automated method for measurement of arteriolar-to-venular diameter ratio (AVR) is presented. The method includes optic disc segmentation for the determination of the AVR measurement zone, retinal vessel segmentation, vessel classification into arteries and veins, selection of major vessel pairs, and measurement of AVRs. The sensitivity for the major vessels in the measurement zone was 87%, while 93% of them were classified correctly into arteries or veins. In 36 out of 40 vessel pairs, at least parts of the paired vessels were correctly identified. Although the average error in the AVRs with respect to those based on the manual vessel segmentation results was 0.11, the average error in vessel diameter was less than 1 pixel. The proposed method may be useful for objective evaluation of AVRs and has a potential for detecting focal arteriolar narrowing on macula-centered screening fundus images.     

Segmentation with gray-scale connectedness can separate arteries and veins in MRA

PURPOSE: To describe and present some preliminary results for a novel algorithm for segmentation with gray-scale connectedness as a means to separate arteries and veins in magnetic resonance angiography (MRA). MATERIALS AND METHODS: The proposed algorithm, SeparaSeed, uses the gray-scale degree of connectedness as a tool to find the zone surrounding each vessel, in order to split the original volume into its different vessel components. In contrast to traditional segmentation methods, no gray-scale information is lost in the process. The segmentation is performed in one step, resulting in a partition of the initial volume into a chosen number of regions of interest (ROIs). Finally, visualization is achieved by projecting the 3D vessel trees to 2D using the common maximum intensity projection (MIP). The algorithm was tested in two MRA data sets of the vessels of the pelvis acquired after injection of an intravascular contrast agent and in one data set of the vessels of the neck with gadolinium. RESULTS: In all data sets, a large proportion of the venous signal was removed while preserving that of the arteries, thus improving visualization of the relevant vessels. CONCLUSION: Separation of arteries and veins is feasible with the proposed algorithm with a moderate amount of interaction.     

Anatomical annotation on vascular structure in volume rendered images

The precise annotation of vascular structure is desired in computer-assisted systems to help surgeons identify each vessel branch. This paper proposes a method that annotates vessels on volume rendered images by rendering their names on them using a two-pass rendering process. In the first rendering pass, vessel surface models are generated using such properties as centerlines, radii, and running directions. Then the vessel names are drawn on the vessel surfaces. Finally, the vessel name images and the corresponding depth buffer are generated by a virtual camera at the viewpoint. In the second rendering pass, volume rendered images are generated by a ray casting volume rendering algorithm that considers the depth buffer generated in the first rendering pass. After the two-pass rendering is finished, an annotated image is generated by blending the volume rendered image with the surface rendered image. To confirm the effectiveness of our proposed method, we performed a computer-assisted system for the automated annotation of abdominal arteries. The experimental results show that vessel names can be drawn on the corresponding vessel surface in the volume rendered images at a computing cost that is nearly the same as that by volume rendering only. The proposed method has enormous potential to be adopted to annotate the vessels in the 3D medical images in clinical applications, such as image-guided surgery.     

Fourier cross-sectional profile for vessel detection on retinal images

Retinal blood vessels are important objects in ophthalmologic images. In spite of many attempts for vessel detection, it appears that existing methodologies are based on edge detection or modeling of vessel cross-sectional profiles in intensity. The application of these methodologies is hampered by the presence of a wide range of retinal vessels. In this paper we define a universal representation for upward and downward vessel cross-sectional profiles with varying boundary sharpness. This expression is used to define a new scheme of vessel detection based on symmetry and asymmetry in the Fourier domain. Phase congruency is utilized for measuring symmetry and asymmetry so that our scheme is invariant to vessel brightness variations. We have performed experiments on fluorescein images and color fundus images to show the efficiency of the proposed algorithm technique. We also have performed a width measurement study, using an optimal medial axis skeletonization scheme as a post-processing step, to compare the technique with the generalized Gaussian profile modeling. The new algorithm technique is promising for automated vessel detection where optimizing profile models is difficult and preserving vessel width information is necessary.     

同步辐射相位对比X线成像技术的初步研究

目的 探讨同步辐射相位对比X线成像技术进行小鼠肝血管成像的试验研究。方法C57BL/6 小鼠6只, 3只开腹,直接结扎所有的进出肝脏的血管和胆管等结构,其余3只则通过门静脉灌注碘造影剂置换小鼠肝内的全部血液后,结扎肝脏的血管和胆总管,然后取出肝脏,所有制成的肝脏标本均放置在4%的甲醛溶液中。标本在北京高能物理研究所的同步辐射国家级实验室进行成像,主要使用同步辐射X线衍射增强成像技术。结果 同步辐射X线衍射增强成像技术在不使用造影剂的情况下即可以显示40μm左右直径的肝脏血管,可以显示血管主干及其8级以上的血管分支。结论 同步辐射X 线衍射增强成像技术具有很高的衬度分辨率和空间分辨率,而且其采用的折射成像机制,可以有效的减少X射线对人体的辐射损伤。     

Automated tracking and computer reproduction of vessels in DSA images

We are developing an automated vessel-tracking method based on the double-square-box region-of-search technique, for efficient tracking of the connected vascular tree in a digital subtraction angiography (DSA) image. Tracking points and branch vessels are located by searching of the perimeter of boxes, which are centered on previously determined tracking points. The most accurate results (90% true-positive rate with six false-positives per image) are obtained by tracking using the double-square-box method. In relatively straight regions of vessels, a large box is employed for efficient tracking; in curved regions of vessels, a small box is employed to ensure accurate tracking. When tracking is completed, accurate vessel information, ie, the vessel position, size, and contrast determined at each tracking point, is available for further quantitative analysis. Computer reproductions of tracked vessel trees appear to correspond well to those in DSA images.     

三段移床三维增强MRA在腹盆及下肢血管病变中的应用

目的　探讨三段移床三维增强MRA 1次全程显示腹盆及下肢血管树的技术及其在血管病变诊断中的作用。方法　 12例腹盆及下肢血管病变的患者 ,男 8例 ,女 4例。 10例同时做了动脉和静脉成像 ,其中动脉血栓形成 5例 ,动脉硬化性闭塞性脉管炎 6例 ,静脉血栓形成 7例 ,下肢静脉炎 3例。其中 5例经DSA证实 ,5例手术证实。扫描序列采用三维快速SPGR序列 ,移床三段扫描。结果　靶血管显示优 9例 ,良 3例。有手术或DSA结果 10例中 ,共有病变段 3 4段 ,其MRA诊断与DSA或手术符合率为 85 .3 %。结论　移床三维增强MRA能使腹主动脉及两侧髂动脉分叉到小腿动脉全程显影 ,还可显示静脉。侧枝循环情况显示优于DSA ,是一种前途广阔的简便的血管检查新方法。     

Retinal image analysis aimed at blood vessel tree segmentation and early detection of neural-layer deterioration

An automatic method of segmenting the retinal vessel tree and estimating status of retinal neural fibre layer (NFL) from high resolution fundus camera images is presented. First, reliable blood vessel segmentation, using 2D directional matched filtering, enables to remove areas occluded by blood vessels thus leaving remaining retinal area available to the following NFL detection. The local existence of rather faint and hardly visible NFL is detected by combining several newly designed local textural features, sensitive to subtle NFL characteristics, into feature vectors submitted to a trained neural-network classifier. Obtained binary retinal maps of NFL distribution show a good agreement with both medical expert evaluations and quantitative results obtained by optical coherence tomography.     

A noncontrast-enhanced pulse sequence optimized to visualize human peripheral vessels

The purpose of this paper is to present a pulse sequence optimized to visualize human peripheral vessels. The optimized MR technique is a 3D multi-shot balanced non-SSFP gradient echo pulse sequence with fat suppression. Several imaging parameters were adjusted to find the best compromise between the contrast of vascular structures and muscle, fat, and bone. Most of the optimization was performed in the knee and calf regions using multi-channel SENSE coils. To verify potential clinical use, images of both healthy volunteers and volunteers with varicose veins were produced. The balanced non-SSFP sequence can produce high-spatial-resolution images of the human peripheral vessels without the need for an intravenous contrast agent. Both arteries and veins are displayed along with other body fluids. Due to the high spatial resolution of the axial plane source or reconstructed images, the need for procedures to separate arteries from veins is limited. We demonstrate that high signals from synovial joint fluid and cystic structures can be suppressed by applying an inversion prepulse but at the expense of reduced image signal-to-noise and overall image quality.     

Visualization of intracranial arteriovenous malformation using multivariate analysis

Intracranial arteriovenous malformations(AVMs) are composed of native deformed vessels where arteries and veins are directly connected in the absence of capillary vessels, and have a complicated three-dimensional(3D) shape. The purpose of this study was to define precisely the location of AVM areas for stereotactic irradiation. The proposed method used a sequence of dynamic X-ray CT images with contrast and opaque media. We analyzed these images by a principal component analysis(PCA) method and extracted component images: artery, vein, and background images. Then we made a fusion image with these three images and displayed the AVM areas. Results showed that the proposed method could identify the physiological location of these AVMs areas. Furthermore, we reconstructed 3D fusion images using two-dimensional component images extracted by the PCA method.     

64层螺旋CT多期扫描减影技术头部血管成像的研究

目的：探讨64层螺旋CT多期扫描减影技术头部血管成像方法及价值。方法：对自发性颅内出血、动脉瘤术后共67例患者行64层螺旋CT平扫、增强动脉期和静脉期扫描获得未减影数据。将动、静脉期数据减去平扫数据获得动脉及混合动静脉的减影数据,静脉期数据减去动脉期数据获得静脉减影数据。采用容积再现（VR）、薄层最大密度投影（TS MIP）重建减影组和未减影组动脉、混合动静脉及静脉图像。根据血管图像质量从很好、好、一般到差分为Ⅰ、Ⅱ、Ⅲ、Ⅳ级。结果：减影组与未减影组血管图像相比去除了动脉、静脉相互的及颅骨的干扰,重建时间更短（8．4±1．5min）。本研究无Ⅳ级图像,减影组图像质量Ⅰ、Ⅱ级动脉共61例（91．0％）,混合动静脉共65例（97．0％）,静脉共62例（92．5％）。两组动脉、混合动静脉图像比较P〉0．05,两组静脉图像比较P〈0．05。结论：64层螺旋CT多期扫描减影头部血管成像是一种安全、快速、可靠的技术,值得临床推广应用。     

A method for 3D reconstruction of coronary arteries using biplane angiography and intravascular ultrasound images

The aim of this study is to describe a new method for the three-dimensional reconstruction of coronary arteries and its quantitative validation. Our approach is based on the fusion of the data provided by intravascular ultrasound images (IVUS) and biplane angiographies. A specific segmentation algorithm is used for the detection of the regions of interest in intravascular ultrasound images. A new methodology is also introduced for the accurate extraction of the catheter path. In detail, a cubic B-spline is used for approximating the catheter path in each biplane projection. Each B-spline curve is swept along the normal direction of its X-ray angiographic plane forming a surface. The intersection of the two surfaces is a 3D curve, which represents the reconstructed path. The detected regions of interest in the IVUS images are placed perpendicularly onto the path and their relative axial twist is computed using the sequential triangulation algorithm. Then, an efficient algorithm is applied to estimate the absolute orientation of the first IVUS frame. In order to obtain 3D visualization the commercial package Geomagic Studio 4.0 is used. The performance of the proposed method is assessed using a validation methodology which addresses the separate validation of each step followed for obtaining the coronary reconstruction. The performance of the segmentation algorithm was examined in 80 IVUS images. The reliability of the path extraction method was studied in vitro using a metal wire model and in vivo in a dataset of 11 patients. The performance of the sequential triangulation algorithm was tested in two gutter models and in the coronary arteries (marked with metal clips) of six cadaveric sheep hearts. Finally, the accuracy in the estimation of the first IVUS frame absolute orientation was examined in the same set of cadaveric sheep hearts. The obtained results demonstrate that the proposed reconstruction method is reliable and capable of depicting the morphology of coronary arteries.     

Pancreatic adenocarcinoma: signs of vascular invasion determined by multi-detector row CT

The purpose of this study was to analyse multi-detector row CT (MDCT) signs of peripancreatic arterial and venous invasion in pancreatic carcinoma. Among 101 patients with pancreatic carcinoma examined by MDCT, 54 candidates for surgery were pre-operatively evaluated for vascular invasion based on MDCT signs. The peripancreatic major vessels (including superior mesenteric artery, coeliac artery, common hepatic artery, superior mesenteric vein and portal vein) were examined carefully by surgeons during the operation. At surgical exploration, 78 of 224 vessels were invaded by tumour. The invaded peripancreatic major arteries (n = 29) and veins (n = 49) presented different MDCT signs: 43% of invaded veins (18/42, except for 7 occluded veins) were surrounded by tumour less than 50% of the vessel circumference compared with 97% (28/29) of the invaded arteries, which were surrounded by tumour more than 50% of the vessel circumference or were embedded in tumour (p<0.001). 69% (34/49) of the invaded veins had vascular stenosis or obliteration, compared with 41% (12/29) of the invaded arteries (p<0.05). Irregularity of the vein wall, 74% (31/42, except for 7 occluded veins); occurred more often than that of the artery wall, 45% (13/29) (p<0.05). In conclusion, the MDCT signs of peripancreatic arterial and venous invasion have different characteristics, which should be considered in pre-operative evaluation.     

Snake modeling and distance transform approach to vascular centerline extraction and quantification

A new method for fully automated centerline extraction and quantification of microvascular structures in confocal microscopy (CM) images is presented. Our method uses the idea of active contour models as well as path planning and distance transforms for the three-dimensional centerline extraction of elongated objects such as vessels. The proposed approach is especially efficient for centerline extraction of complex branching structures. The method performance is validated in several CM images of both normal and stroked rat brains as well as simulated objects. The results confirm the efficiency of the proposed method in extracting the medial curve of vessels, which is essential for the computation of quantitative parameters.     

Quantification of blood vessel calibre in retinal images of multi-ethnic school children using a model based approach

Changes and variation in retinal vessel width are related to vascular risk factors and prospectively related to cardiovascular disease in later life. Hence, assessment of vessel width may be a useful physio-marker and potential predictor of cardiovascular status. However, measurement of vessel calibre from retinal images is a challenging process to automate. This paper proposes an automated system to measure vessel calibre in retinal images, which is demonstrated in images of multi-ethnic school children. The diameter measurement is based on the detection of the centreline pixels from a vessel probability map image, determining the vessel orientation at these pixels, extracting the vessel segments and later using a two-dimensional model, which is optimized to fit various types of intensity profiles of vessel segments. The width is then estimated from parameters of the optimized model. The method is also quantitatively analyzed using monochromatic representations of different colour spaces. The algorithm is evaluated on a recently introduced public database CHASE_DB1, which is a subset of retinal images of multi-ethnic children from the Child Heart and Health Study in England (CHASE) dataset. Moreover, the precise estimation of retinal vascular widths is critical for epidemiologists to identify the risk factors. This work also introduces an interactive software tool for epidemiologists, with which retinal vessel calibre can be precisely marked.     

三维动态增强磁共振血流成像对指导肺癌手术的价值

目的：研究三维动态增强磁共振血流成像（3D DCE MRA）对肺癌侵犯血管的显示能力，探讨MRA术前对手术计划的指导价值。方法：肺癌患26例，除常规MR检查处，注射Gd-DTPA 0.2mmol/kg后，冠状面动态三维超快速梯度回波采集，最大强度投影法（MIP）重建。分析肺癌与血管的关系，与手术病理对照。结果：26例中25例肺部不同时相的血管显示清晰，9例肿瘤贴邻血管，另16例可见肿瘤粘连或包绕大血管。结论：3D DCE MRA可清晰显示肺段以上的肺动脉和肺静脉，对术前判断肿瘤能否切除及手术切除的范围有指导意义。     

Multi-scale retinal vessel segmentation using line tracking

In this paper an algorithm for vessel segmentation and network extraction in retinal images is proposed. A new multi-scale line-tracking procedure is starting from a small group of pixels, derived from a brightness selection rule, and terminates when a cross-sectional profile condition becomes invalid. The multi-scale image map is derived after combining the individual image maps along scales, containing the pixels confidence to belong in a vessel. The initial vessel network is derived after map quantization of the multi-scale confidence matrix. Median filtering is applied in the initial vessel network, restoring disconnected vessel lines and eliminating noisy lines. Finally, post-processing removes erroneous areas using directional attributes of vessels and morphological reconstruction.The experimental evaluation in the publicly available DRIVE database shows accurate extraction of vessels network. The average accuracy of 0.929 with 0.747 sensitivity and 0.955 specificity is very close to the manual segmentation rates obtained by the second observer. The proposed algorithm is compared also with widely used supervised and unsupervised methods and evaluated in noisy conditions, giving higher average sensitivity rate in the same range of specificity and accuracy, and showing robustness in the presence of additive Salt&Pepper or Gaussian white noise.     

Vessel‐encoded dynamic magnetic resonance angiography using arterial spin labeling

A new noninvasive MRI method for vessel‐selective angiography is presented. The technique combines vessel‐encoded pseudocontinuous arterial spin labeling with a two‐dimensional dynamic angiographic readout and was used to image the cerebral arteries in healthy volunteers. Time‐of‐flight angiograms were also acquired prior to vessel‐selective dynamic angiography acquisitions in axial, coronal, and/or sagittal planes, using a 3‐T MRI scanner. The latter consisted of a vessel‐encoded pseudocontinuous arterial spin labeling pulse train of 300 or 1000 ms followed by a two‐dimensional thick‐slab flow‐compensated fast low‐angle shot readout combined with a segmented Look‐Locker sampling strategy (temporal resolution = 55 ms). Selective labeling was performed at the level of the neck to generate individual angiograms for both right and left internal carotid and vertebral arteries. Individual vessel angiograms were reconstructed using a bayesian inference method. The vessel‐selective dynamic angiograms obtained were consistent with the time‐of‐flight images, and the longer of the two vessel‐encoded pseudocontinuous arterial spin labeling pulse train durations tested (1000 ms) was found to give better distal vessel visibility. This technique provides highly selective angiograms quickly and noninvasively that could potentially be used in place of intra‐arterial x‐ray angiography for larger vessels. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Vessel‐encoded dynamic magnetic resonance angiography using arterial spin labeling

A new noninvasive MRI method for vessel selective angiography is presented. The technique combines vessel‐encoded pseudocontinuous arterial spin labeling with a two‐dimensional dynamic angiographic readout and was used to image the cerebral arteries in healthy volunteers. Time‐of‐flight angiograms were also acquired prior to vessel‐selective dynamic angiography acquisitions in axial, coronal, and/or sagittal planes, using a 3‐T MRI scanner. The latter consisted of a vessel‐encoded pseudocontinuous arterial spin labeling pulse train of 300 or 1000 ms followed by a two‐dimensional thick‐slab flow‐compensated fast low angle shot readout combined with a segmented Look‐Locker sampling strategy (temporal resolution = 55 ms). Selective labeling was performed at the level of the neck to generate individual angiograms for both right and left internal carotid and vertebral arteries. Individual vessel angiograms were reconstructed using a bayesian inference method. The vessel‐selective dynamic angiograms obtained were consistent with the time‐of‐flight images, and the longer of the two vessel‐encoded pseudocontinuous arterial spin labeling pulse train durations tested (1000 ms) was found to give better distal vessel visibility. This technique provides highly selective angiograms quickly and noninvasively that could potentially be used in place of intra‐arterial x‐ray angiography for larger vessels. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

彩色多普勒超声诊断肢体血管疾病

目的：提高彩色多普勒超声在肢体血管性疾病的诊断率。材料和方法：利用彩色多普勒超声和双工多普勒超声技术对３２例血管疾病进行了检查，其中肢体动脉性疾病８例，肢体静脉性疾病２４例。结果：各种肢体血管性疾病在血流方向、速度、血流性质以及频谱形态等方面有其各自相对特异的超声表现。结论：彩色多普勒超声对肢体动静脉疾病既有安全、无创、双侧对比容易的优点，又可直接确定受累动静脉的损害部位，有助于早期诊断，治疗和预防。