Vessel Path Research Articles

An Improved A-Star Algorithm Considering Water Current, Traffic Separation and Berthing for Vessel Path Planning

A traditional A-Star (A*) algorithm generates an optimal path by minimizing the path cost. For a vessel, factors of path length, obstacle collision risk, traffic separation rule and manoeuvrability restriction should be all taken into account for path planning. Meanwhile, the water current also plays an important role in voyaging and berthing for vessels. In consideration of these defects of the traditional A-Star algorithm when it is used for vessel path planning, an improved A-Star algorithm has been proposed. To be specific, the risk models of obstacles (bridge pier, moored or anchored ship, port, shore, etc.) considering currents, traffic separation, berthing, manoeuvrability restriction have been built firstly. Then, the normal path generation and the berthing path generation with the proposed improved A-Star algorithm have been represented, respectively. Moreover, the problem of combining the normal path and the berthing path has been also solved. To verify the effectiveness of the proposed A-Star path planning methods, four cases have been studied in simulation and real scenarios. The results of experiments show that the proposed A-Star path planning methods can deal with the problems denoted in this article well, and realize the trade-off between the path length and the navigation safety.

Stretchable, Implantable, Nanostructured Flow-Diverter System for Quantification of Intra-aneurysmal Hemodynamics.

Random weakening of an intracranial blood vessel results in abnormal blood flow into an aneurysmal sac. Recent advancements show that an implantable flow diverter, integrated with a medical stent, enables a highly effective treatment of cerebral aneurysms by guiding blood flow into the normal vessel path. None of such treatment systems, however, offers post-treatment monitoring to assess the progress of sac occlusion. Therefore, physicians rely heavily on either angiography or magnetic resonance imaging. Both methods require a dedicated facility with sophisticated equipment settings and time-consuming, cumbersome procedures. In this paper, we introduce an implantable, stretchable, nanostructured flow-sensor system for quantification of intra-aneurysmal hemodynamics. The open-mesh membrane device is capable of effective implantation in complex neurovascular vessels with extreme stretchability (500% radial stretching) and bendability (180° with 0.75 mm radius of curvature) for monitoring of the treatment progress. A collection of quantitative mechanics, fluid dynamics, and experimental studies establish the fundamental aspects of design criteria for a highly compliant, implantable device. Hemocompatibility study using fresh ovine blood captures the device feasibility for long-term insertion in a blood vessel, showing less platelet deposition compared to that in existing implantable materials. In vitro demonstrations of three types of flow sensors show quantification of intra-aneurysmal blood flow in a pig aorta and the capability of observation of aneurysm treatment with a great sensitivity (detection limit as small as 0.032 m/s). Overall, this work describes a mechanically soft flow-diverter system that offers an effective treatment of aneurysms with an active monitoring of intra-aneurysmal hemodynamics.

A New Definition of an Acupuncture Meridian

This article provides a new definition of an acupuncture meridian. It suggests that a meridian consists of a distal tract of tissue that is affected by organ function. In the 1960s, Kim discovered the primo vascular system and regarded the superficial primo vessels as equating to the meridians. Instead, this article suggests that the superficial primo vessels merely underlie the meridians, in that they enable their creation, which is why some meridians are said to occur along the paths of superficial primo vessels. But the meridians themselves do not have a dedicated anatomical structure; instead they are merely tracts of tissue whose normal function is impeded when the related abdominal organ is stressed. It is hypothesized that the organ information is communicated in electrical waves that may travel through the connective tissue sheaths of the superficial primo vessels. Hence, the primo vessels serve as an inadvertent transport for this information, but the organ information is independent of the physiological purpose of the primo vascular system, as are the resultant meridians.

Correlation between epicardial adipose tissue thickness and the degree of coronary artery atherosclerosis

Background/aim: The purpose of the current study was to evaluate the thickness of the epicardial adipose tissue and its association with the degree of coronary artery disease in a group of autopsied cases. Materials and methods: A number of 79 cases were included in the study. Five preestablished incisions of the epicardial adipose tissue (EAT) were made on each of the hearts. These five points were next to/on the path of the major coronary vessels. The degree of coronary atherosclerosis was evaluated during the autopsy. Results: The results revealed the greatest thickness of the EAT on the incision made on the anterior and posterior wall of the right ventricle. EAT was thicker in cases presenting atherosclerosis degree I or II in two of the coronary arteries, the left circumflex artery and left main artery; on the left anterior descending artery, higher EAT thickness associated with fourth degree atherosclerosis. Conclusion: Epicardial adipose tissue thickness was greater at the incision points situated on the right side of the heart. Greater EAT thickness was associated significantly with early atherosclerosis development in three of the coronary arteries (LCx, LMA, LADA).

ANALYSIS OF SHIP BEHAVIOR UNDER INFLUENCE OF WAVES AND CURRENTS

The most important environmental factors related to safety of ship and performance on high sea are surface winds and waves. In order to obtain an optimal trajectory of a ship route, it is a prerequisite to know the sea state condition, as well as, the behavior of the ship in waves and currents. The purpose of this study is to analyze the ship behavior under the influence of 3 different sea state conditions over the Southern Brazilian inner shelf near the Rio Grande coastal region. SHIPMOVE and TOMAWAC + TELEMAC3D system were simulated under three different wave scenarios. Day 4 showed the shortest traveled distance and lowest velocity. The sea state of Day 33 deflected the initial vessel path northeasterly and generated high rotational motions. Day 100 depicted the longest final displacement and highest average velocity, where this event showed the most smooth sea state condition. Lastly, the ship behavior seems to be strongly influenced by the sea state condition for the three events.

Inferred fish behavior its implications for hydroacoustic surveys in nearshore habitats

Population availability and vessel avoidance effects on hydroacoustic abundance estimates may be scale dependent; therefore, it is important to evaluate these biases across systems. We performed an inter-ship comparison survey to determine the effect of vessel size, day-night period, depth, and environmental gradients on walleye (Sander vitreus) density estimates in Lake Erie, an intermediate-scaled system. Consistent near-bottom depth distributions coupled with horizontal fish movements relative to vessel paths indicated avoidance behavior contributed to higher walleye densities from smaller vessels in shallow water (i.e., <15m), although the difference decreased with increasing depth. Diel bank migrations in response to seasonally varying onshore-to-offshore environmental gradients likely contributed to day-night differences in densities between sampling locations and seasons. Spatial and unexplained variation accounted for a high proportion of total variation; however, increasing sampling intensity can mitigate effects on precision. Therefore, researchers should minimize systematic avoidance and availability related biases (i.e., vessel and day-night period) to improve population abundance estimates. Quantifying availability and avoidance behavior effects and partitioning sources of variation provides informed flexibility for designing future hydroacoustic surveys in shallow-water nearshore environments.

Assessment of impacts and potential mitigation for icebreaking vessels transiting pupping areas of an ice-breeding seal

Icebreaker operations in the Arctic and other areas are increasing rapidly to support new industrial activities and shipping routes, but the impact on pinnipeds in these habitats is poorly explored. We present the first quantitative study of icebreakers transiting ice-breeding habitat of a phocid seal and recommendations for mitigation. Impacts were recorded from the vessel bridge during seven ice seasons 2006–2013, for Caspian seals (Pusa caspica) breeding on the winter ice-field of the Caspian Sea. Impacts included displacement and separation of mothers and pups, breakage of birth or nursery sites and vessel-seal collisions. The flight distance of mothers with pups ahead was <100m, but measurable disturbance occurred at distances exceeding 200m. Separation distances of pups from mothers were greatest for seals <10m to the side of the vessel, and declined with increasing distance from the vessel. The relative risk of separation by ≥20m was greatest for distances <50m from the vessel path. Seals on flat ice were more likely to be separated or displaced by ≥20m than seals in an ice rubble field. The relative risk of vessel collisions with mothers or pups was significantly greater at night when breaking new channels (12.6 times), with vessel speeds ≥4kn (7.8 times). A mitigation hierarchy is recommended for the Caspian Sea which could be applied to Arctic pinnipeds, including reducing icebreaker transits during critical periods, and using data from aerial surveys to plan routes to minimise encounters with seals. Where pre-emptive avoidance is not possible, recommendations include maintaining a safe separation from breeding seals at least 50m beyond the distance at which measurable disturbance occurs, speed limits, use of thermal imaging at night, dedicated on-board Seal Observers, and training of vessel officers to take effective reactive measures.

Analysis of Vessel Connectivities in Retinal Images by Cortically Inspired Spectral Clustering

Retinal images provide early signs of diabetic retinopathy, glaucoma, and hypertension. These signs can be investigated based on microaneurysms or smaller vessels. The diagnostic biomarkers are the change of vessel widths and angles especially at junctions, which are investigated using the vessel segmentation or tracking. Vessel paths may also be interrupted; crossings and bifurcations may be disconnected. This paper addresses a novel contextual method based on the geometry of the primary visual cortex (V1) to study these difficulties. We have analyzed the specific problems at junctions with a connectivity kernel obtained as the fundamental solution of the Fokker-Planck equation, which is usually used to represent the geometrical structure of multi-orientation cortical connectivity. Using the spectral clustering on a large local affinity matrix constructed by both the connectivity kernel and the feature of intensity, the vessels are identified successfully in a hierarchical topology each representing an individual perceptual unit.

Verification of Route Choice Model and Operational Model of Vessel Traffic

Because of ever-increasing economic globalization, it is necessary to simulate vessel behavior for investigating safety and capacity in ports and inland waterways. A new maritime traffic model was developed; it comprises two parts: the route choice model and the operational model. This paper presents the operational model, which describes vessel sailing behavior by optimal control. In the operational model, the main behavioral assumption is that all actions of the bridge team, such as accelerating and turning, are executed to force the vessel to sail with the desired speed and course. In the proposed theory, deviating from the desired speed and course, accelerating, decelerating, and turning will provide disutility (cost) to the vessel. Through prediction and minimization of this disutility, the longitudinal and angular acceleration can be optimized and predict individual vessel sailing behavior. To verify the route choice model and the operational model, a case study was carried out; it applied the models to predict individual vessel behavior (path, speed, and course) in the entrance channel to Maasvlakte I at the Port of Rotterdam, Netherlands. The simulation results show a good prediction of the vessel path and vessel course. As no other model has been built specifically to predict vessel behavior in the port area, the current methods provide a fundamental basis for investigating vessel behavior in restricted waterways. In addition, this research showed the potential of the model to increase the safety and capacity of ports and inland waterways.

Traffic Jam Response

Congenital heart disease in newborns exhibits a spectrum of defects, one of which is the occlusion of the vascular conduits of the arteries. For students first learning about cardiovascular lesions, the tortuous path of blood vessels can be visually overwhelming to the untrained eye, and useful models are needed to help deconstruct the morphological complexity of heart chambers and vessel location during heart development and disease. Here, I present two hands-on activities to explore how pulmonary artery stenosis may have dire consequences, such as cardiac muscle cell hypertrophy. These activities will not only help students explore genetic aberrations associated with congenital heart diseases, but will also encourage them to think about how to develop molecular and cellular strategies that fix primary obstruction in other branched organs such as the gut, kidney, and pancreas.

A simplified method for quantifying the subject-specific relationship between blood pressure and carotid-femoral pulse wave velocity.

Devices that estimate blood pressure from arterial pulse wave velocity (PWV) potentially provide continuous, ambulatory blood pressure monitoring. Accurate blood pressure estimation requires reliable quantification of the relationship between blood pressure and PWV. Regression to population normal values or, when using limb artery PWV, changing hydrostatic blood pressure within the limb provides a calibration index. Population lookup tables require accurate anthropometric correlates, assuming no individual variation. Only devices that measure PWV in the limb can use limb position changes. This study proposes a method for developing a calibration curve independent of lookup tables and useful for large artery PWV measurement, such as carotid-femoral PWV (PWVcf). PWVcf was measured in 27 normal subjects (15 female, 36±19 years) in both the supine and standing position. The change in systemic pressure was measured and hydrostatic pressure change calculated from estimated vessel path length height, measured using body surface distances. Brachial diastolic blood pressure increased for all subjects from supine to standing (supine 70±8 mmHg, standing 83±8 mmHg, p<;0.001) with an additional hydrostatic change across the carotid-femoral path length of 19±2 mmHg (p<;0.001). PWVcf also increased in all subjects (supine 5.2±1.3 m/s, standing 7.3±2.2 m/s, p<;0.001). The subject-specific calibration index (ΔDP/ΔPWVcf) varied amongst the cohort (20±8 mmHg/m/s), was correlated with age (-0.57, p=0.002) and seated aortic systolic pressure (-0.38, p=0.048) and was always greater than zero. Thus, this study describes a simple but novel method of measuring an individualized calibration index using blood pressure and PWV measurements in the supine and standing position.

Interactive virtual stent planning for the treatment of coarctation of the aorta.

The coarctation of the aorta (CoA), a local narrowing of the aortic arch, accounts for 7 % of all congenital heart defects. Stenting is a recommended therapy to reduce the pressure gradient. This procedure is associated with complications such as the development of adverse flow conditions. A computer-aided treatment planning based on flow simulations can help to predict possible complications. The virtual stent planning is an important, intermediate step in the treatment planning pipeline. We present a novel approach that automatically suggests a stent setup and provides a set of intuitive parameters that allow for an interactive adaption of the suggested stent placement and induced deformation. A high-quality mesh and a centerline are automatically generated. The stent-induced deformation is realized through a deformation of the centerline and a vertex displacement with respect to the deformed centerline and additional stent parameters. The parameterization is automatically derived from the underlying data and can be optionally altered through a condensed set of clinically sound parameters. The automatic deformation can be generated in about 25 s on a consumer system. The interactive adaption can be performed in real time. Compared with manual expert reconstructions of the stented vessel section, the mean difference of vessel path and diameter is below 1 mm. Our approach enables a medical user to easily generate a plausibly deformed vessel mesh which is necessary as input for a simulation-based treatment planning of CoA.

Fast 4D flow MRI intracranial segmentation and quantification in tortuous arteries.

To describe, validate, and implement a centerline processing scheme (CPS) for semiautomated segmentation and quantification in carotid siphons of healthy subjects. 4D flow MRI enables blood flow measurement in all major cerebral arteries with one scan. Clinical translational hurdles are time demanding postprocessing and user-dependence induced variability during analysis. A CPS for 4D flow data was developed to automatically separate cerebral artery trees. Flow parameters were quantified at planes along the centerline oriented perpendicular to the vessel path. At 3T, validation against 2D phase-contrast (PC) magnetic resonance imaging (MRI) and 4D flow manual processing was performed on an intracranial flow phantom for constant flow, while pulsatile flow validation was performed in the internal carotid artery (ICA) of 10 healthy volunteers. The CPS and 4D manual processing times were measured and compared. Flow and area measurements were also demonstrated along the length of the ICA siphon. Phantom measurements for area and flow were highly correlated between the CPS and 2D measurements (area: R = 0.95, flow: R = 0.94), while in vivo waveforms were highly correlated (R = 0.93). Processing time was reduced by a factor of 4.6 compared with manual processing. Whole ICA measurements revealed a significantly decreased area in the most distal segment of the carotid siphon (P = 0.0017), with flow unchanged (P = 0.84). This study exhibits fast semiautomated analysis of intracranial 4D flow MRI. Internal consistency was shown through flow conservation along the tortuous ICA siphon, which is typically difficult to assess.

Operation and force analysis of the guide wire in a minimally invasive vascular interventional surgery robot system

To develop a robot system for minimally invasive surgery is significant, however the existing minimally invasive surgery robots are not applicable in practical operations, due to their limited functioning and weaker perception. A novel wire feeder is proposed for minimally invasive vascular interventional surgery. It is used for assisting surgeons in delivering a guide wire, balloon and stenting into a specific lesion location. By contrasting those existing wire feeders, the motion methods for delivering and rotating the guide wire in blood vessel are described, and their mechanical realization is presented. A new resistant force detecting method is given in details. The change of the resistance force can help the operator feel the block or embolism existing in front of the guide wire. The driving torque for rotating the guide wire is developed at different positions. Using the CT reconstruction image and extracted vessel paths, the path equation of the blood vessel is obtained. Combining the shapes of the guide wire outside the blood vessel, the whole bending equation of the guide wire is obtained. That is a risk criterion in the delivering process. This process can make operations safer and man-machine interaction more reliable. A novel surgery robot for feeding guide wire is designed, and a risk criterion for the system is given.

Intra-vascular blood velocity and volumetric flow rate calculated from dynamic 4D CT angiography using a time of flight technique.

We examine a time of flight (TOF) approach for the analysis of contrast enhanced 4D volumetric CT angiography scans to derive and display blood velocity in arteries. Software was written to divide blood vessels into a series of cross sections and to track contrast bolus TOF along the central vessel axis, which was defined by a user, from 4D CT source data. Time density curves at each vessel cross section were fit with quadratic, Gaussian, and gamma variate functions to determine bolus time to peak (TTP). A straight line was used to plot TTP versus vessel path length for all three functions and the slope used to calculate intraluminal velocity. Software was validated in a simulated square channel and non-pulsatile flow phantom prior to the calculation of blood velocity in the major cerebral arteries of 8 normal patients. The TOF algorithm correctly calculates intra-luminal fluid velocity in eight flow conditions of the CT flow phantom where quadratic functions were used. Across all conditions, in phantoms and in vivo, the success of calculations depended strongly on having a sufficiently long path length to make measurements and avoiding venous contamination. Total blood flow into the brain was approximately 17 % of a normal 5 L cardiac output. The technique was explored in vivo in a patient with subclavian steal syndrome, in the pulmonary arteries and in the iliac artery from clinical 4D CT source data. Intravascular blood velocity and flow may be calculated from 4D CT angiography using a TOF approach.

The Role for Adjunctive Image in Pre-procedural Assessment and Peri-Procedural Management in Chronic Total Occlusion Recanalisation

Non invasive coronary angiography with multislice computed tomography has exquisite sensitivity to detect calcium and even the faintest late contrast filling of the distal vessel. Calcium burden and occlusion length are still valuable markers of duration, complexity and success of the recanalisation procedure. The ability to visualise the vessel also in the occluded segment, especially if calcified, can also help the operator to understand where to pierce the proximal cap in stumpless occlusions and to predict unusual courses, especially in very tortuous arteries. Imaging side by side CT images and angiography during the recanalisation procedure is an established practice in many active CTO laboratories and algorithms for co-registration are designed to overcome the challenges of systo-diastolic and respiratory motion. Intravascular ultrasound is used in almost all cases by the experienced Japanese CTO operators but most of the times its main use is a better identification of the diseased segment after predilatation to ensure complete stent cover and appropriate stent expansion, an application similar to other complex non occlusive lesions. The specificity of IVUS during CTO recanalisation is the identification of the vessel path in stumpless occlusions and the guidance of wire reentry especially during reverse Controlled Retrograde Anterograde Tracking. Optical coherence tomography has limitations in the setting of CTO recanalisation because of the need of forceful contrast flushing to clear blood, contraindicated in the presence of anterograde dissections, and the limited penetration. The variability in the use of both non-invasive and invasive imaging during CTO recanalisation is immense, going from more than 90% in Japan to less than 20% in Europe and intermediate penetration in the USA. Probably the explanation is almost only in availability and cost because all countries see a progressive increase of use suggesting that these methods are becoming an established tool for guidance of CTO recanalisation.

Impact of a New Motion-Correction Algorithm on Image Quality of Low-Dose Coronary CT Angiography in Patients with Insufficient Heart Rate Control

Prospective electrocardiogram (ECG) triggering allows coronary computed tomography angiography (CCTA) scanning with low radiation dose but requires heart rates below 63 beats/min. We assessed the impact of a novel vendor-specific motion-correction algorithm on image quality and interpretability of low-dose CCTA acquired despite insufficient heart rate control. In 40 patients undergoing CCTA for the assessment of known or suspected coronary artery disease who did not reach the target heart rate below 63 beats/min despite β-blockade before prospective low-dose scanning, the temporal acquisition window was increased (80 ms additional padding). The new algorithm detects and integrates vessel path and velocity from adjacent cardiac phases for motion correction. Two blinded observers assessed image quality on a 4-point Likert scale (1, nonevaluative; 2, reduced but evaluative; 3, good; and 4, excellent) and the fraction of interpretable segments (score 2 or more) using motion correction versus standard reconstruction. Image reconstruction with motion correction resulted in an increased median coronary artery image quality score (excellent interobserver agreement, κ = 0.85) compared to standard reconstruction (3.4 vs. 3.0, P < .001). Consequently, motion-corrected reconstruction significantly improved the overall interpretability of coronary arteries (from 78% to 88%, P < .001). Estimated mean effective radiation dose was 2.3 ± 0.8 mSv. A novel, vendor-specific, motion-corrected, reconstruction algorithm improves image quality and interpretability of prospectively ECG-triggered low-dose CCTA despite insufficient heart rate control.

Retinal Vessel Detection and Measurement for Computer-aided Medical Diagnosis

Since blood vessel detection and characteristic measurement for ocular retinal images is a fundamental problem in computer-aided medical diagnosis, automated algorithms/systems for vessel detection and measurement are always demanded. To support computer-aided diagnosis, an integrated approach/solution for vessel detection and diameter measurement is presented and validated. In the proposed approach, a Dempster-Shafer (D-S)-based edge detector is developed to obtain initial vessel edge information and an accurate vascular map for a retinal image. Then, the appropriate path and the centerline of a vessel of interest are identified automatically through graph search. Once the vessel path has been identified, the diameter of the vessel will be measured accordingly by the algorithm in real time. To achieve more accurate edge detection and diameter measurement, mixed Gaussian-matched filters are designed to refine the initial detection and measures. Other important medical indices of retinal vessels can also be calculated accordingly based on detection and measurement results. The efficiency of the proposed algorithm was validated by the retinal images obtained from different public databases. Experimental results show that the vessel detection rate of the algorithm is 100% for large vessels and 89.9% for small vessels, and the error rate on vessel diameter measurement is less than 5%, which are all well within the acceptable range of deviation among the human graders.

A novel method for retinal vessel tracking using particle filters

Extraction of a proper map from the vessel paths in the retinal images is a prerequisite for many applications such as identification. In this paper, we present a new approach based on particle filtering to determine and locally track the vessel paths in retina. Particle filter needs to use an acceptable probability density function (PDF) describing the blood vessels which must be provided by the retinal image. For this purpose, the product of the green and blue channels of the RGB retinal images is considered and after a median filtering stage, it is used as a PDF for tracking procedure. Then a stage of optic disc localization is performed to localize the starting points around the optic disc. With a proper set of starting points, the iterative tracking procedure initiates. First, a uniform propagation of the particles on an annular ring around each point (including starting points or ones determined as central points in the previous iteration) is performed. The particle weights are evaluated and accordingly, each particle is decided to be inside or outside the vessel. The subsequent stage is to analyze the hypothetical vectors between a central point and each of the inside vessel particles to find ones located inside vessel. Afterwards, the particles are clustered using quality threshold clustering method. Finally, each cluster introduces a central point for pursuing the tracking procedure in the next iteration. The tracking proceeds towards a bifurcation or the end of the vessels. We introduced two criteria: automatic/manually tracked ratio (AMTR) and false/manually tracked ratio (FMTR) for evaluating the tracking results. Apart from the labeling accuracy, the average values of AMTR and FMTR were 0.7746 and 0.2091, respectively. The proposed method successfully deals with the bifurcations with robustness against noise and tracks the thin vessels.

COLOR AND POWER DOPPLER ULTRASONOGRAPHY FOR CHARACTERIZATION OF SPLENIC MASSES IN DOGS

Benign and malignant splenic masses can appear similar on B-mode imaging, making ultrasound sensitive but not specific in their diagnosis. Our goal was to characterize color and/or power Doppler characteristics of vasculature within and adjacent to a splenic mass, which would distinguish benign vs. malignant lesions. The hypothesis was that malignant splenic masses will have altered vascular patterns compared with benign masses. Color and power Doppler cineloops evaluating the vasculature within the mass and normal splenic parenchyma were obtained in sagittal and transverse planes using a standardized protocol. Categories of evaluation included presence of peritoneal effusion, a large aberrant or tortuous vessel within the mass, relative blood flow within the mass compared with normal parenchyma, and path of vessels in the adjacent parenchyma entering into the mass. All patients had histopathologic or definitive cytologic diagnosis. Thirty-one dogs were included. There were 13 malignant masses and 18 were benign. Peritoneal effusion was significantly associated with malignancy (P = 0.0007). Presence of an aberrant or tortuous vessel within the mass was nearly significant (P = 0.059). There was no significant difference in any of the color or power Doppler blood flow evaluations. Ultrasonographic findings of a splenic mass and peritoneal effusion may indicate malignancy. The presence of an aberrant vessel within a splenic mass could suggest malignancy; however more data are needed.