Vessel Cross-section Research Articles

Novel mathematical approach to accurately quantify 3D endothelial cell morphology and vessel geometry based on fluorescently marked endothelial cell contours: Application to the dorsal aorta of wild-type and Endoglin-deficient zebrafish embryos.

Endothelial cells, which line the lumen of blood vessels, locally sense and respond to blood flow. In response to altered blood flow dynamics during early embryonic development, these cells undergo shape changes that directly affect vessel geometry: In the dorsal aorta of zebrafish embryos, elongation of endothelial cells in the direction of flow between 48 and 72 hours post fertilization (hpf) reduces the vessel's diameter. This remodeling process requires Endoglin; excessive endothelial cell growth in the protein's absence results in vessel diameter increases. To understand how these changes in vessel geometry emerge from morphological changes of individual endothelial cells, we developed a novel mathematical approach that allows 3D reconstruction and quantification of both dorsal aorta geometry and endothelial cell surface morphology. Based on fluorescently marked endothelial cell contours, we inferred cross-sections of the dorsal aorta that accounted for dorsal flattening of the vessel. By projection of endothelial cell contours onto the estimated cross-sections and subsequent triangulation, we finally reconstructed 3D surfaces of the individual cells. By simultaneously reconstructing vessel cross-sections and cell surfaces, we found in an exploratory analysis that morphology varied between endothelial cells located in different sectors of the dorsal aorta in both wild-type and Endoglin-deficient zebrafish embryos: In wild-types, ventral endothelial cells were smaller and more elongated in flow direction than dorsal endothelial cells at both 48 hpf and 72 hpf. Although dorsal and ventral endothelial cells in Endoglin-deficient embryos had similar sizes at 48 hpf, dorsal endothelial cells were much larger at 72 hpf. In Endoglin-deficient embryos, elongation in flow direction increased between 48 hpf and 72 hpf in ventral endothelial cells but hardly changed in dorsal endothelial cells. Hereby, we provide evidence that dorsal endothelial cells contribute most to the disparate changes in dorsal aorta diameter in wild-type and Endoglin-deficient embryos between 48 hpf and 72 hpf.

Hemodynamic Characteristics of a Tortuous Microvessel Using High-Fidelity Red Blood Cell Resolved Simulations.

Tortuous microvessels are characteristic of microvascular remodeling associated with numerous physiological and pathological scenarios. Three-dimensional (3D) hemodynamics in tortuous microvessels influenced by red blood cells (RBCs), however, are largely unknown, and important questions remain. Is blood viscosity influenced by vessel tortuosity? How do RBC dynamics affect wall shear stress (WSS) patterns and the near-wall cell-free layer (CFL) over a range of conditions? The objective of this work was to parameterize hemodynamic characteristics unique to a tortuous microvessel. RBC-resolved simulations were performed using an immersed boundary method-based 3D fluid dynamics solver. A representative tortuous microvessel was selected from a stimulated angiogenic network obtained from imaging of the rat mesentery and digitally reconstructed for the simulations. The representative microvessel was a venule with a diameter of approximately 20 μm. The model assumes a constant diameter along the vessel length and does not consider variations due to endothelial cell shapes or the endothelial surface layer. Microvessel tortuosity was observed to increase blood apparent viscosity compared to a straight tube by up to 26%. WSS spatial variations in high curvature regions reached 23.6 dyne/cm2 over the vessel cross-section. The magnitudes of WSS and CFL thickness variations due to tortuosity were strongly influenced by shear rate and negligibly influenced by tube hematocrit levels. New findings from this work reveal unique tortuosity-dependent hemodynamic characteristics over a range of conditions. The results provide new thought-provoking information to better understand the contribution of tortuous vessels in physiological and pathological processes and help improve reduced-order models.

Effect of variability of mechanical properties on the predictive capabilities of vulnerable coronary plaques

Background and Objective:Coronary plaque rupture is a precipitating event responsible for two thirds of myocardial infarctions. Currently, the risk of plaque rupture is computed based on demographic, clinical, and image-based adverse features. However, using these features the absolute event rate per single higher-risk lesion remains low. This work studies the power of a novel framework based on biomechanical markers accounting for material uncertainty to stratify vulnerable and non-vulnerable coronary plaques. Methods:Virtual histology intravascular ultrasounds from 55 patients, 29 affected by acute coronary syndrome and 26 affected by stable angina pectoris, were included in this study. Two-dimensional vessel cross-sections for finite element modeling (10 sections per plaque) incorporating plaque structure (medial tissue, loose matrix, lipid core and calcification) were reconstructed. A Montecarlo finite element analysis was performed on each section to account for material variability on three biomechanical markers: peak plaque structural stress at diastolic and systolic pressure, and peak plaque stress difference between systolic and diastolic pressures, together with the luminal pressure. Machine learning decision tree classifiers were trained on 75% of the dataset and tested on the remaining 25% with a combination of feature selection techniques. Performance against classification trees based on geometric markers (i.e., luminal, external elastic membrane and plaque areas) was also performed. Results:Our results indicate that the plaque structural stress outperforms the classification capacity of the combined geometric markers only (0.82 vs 0.51 area under curve) when accounting for uncertainty in material parameters. Furthermore, the results suggest that the combination of the peak plaque structural stress at diastolic and systolic pressures with the maximum plaque structural stress difference between systolic and diastolic pressures together with the systolic pressure and the diastolic to systolic pressure gradient is a robust classifier for coronary plaques when the intrinsic variability in material parameters is considered (area under curve equal to [0.91–0.93]). Conclusion:In summary, our results emphasize that peak plaque structural stress in combination with the patient’s luminal pressure is a potential classifier of plaque vulnerability as it independently considers stress in all directions and incorporates total geometric and compositional features of atherosclerotic plaques.

Mixing properties of coronary infusion catheters assessed by in vitro experiments and computational fluid dynamics.

Continuous infusion thermodilution is an established technique for the assessment of absolute coronary blood flow and microvascular resistance due to its proven accuracy and reproducibility. However, for this technique to yield reliable measurements, direct and homogenous mixing of injected saline and blood is mandatory. This study aimed to assess and compare the mixing properties of two different microcatheters, namely the Rayflow® (with sideholes for infusion) and the Finecross® catheter (single end-hole for infusion), which are commonly used in the catheterization laboratory. The study employed three different methods to evaluate the mixing properties of the catheters. Firstly, a qualitative assessment of mixing was performed using ink injections in an in vitro bench model of a coronary artery. Secondly, in analogy to the human catheterization laboratory, mixing properties over the length of the coronary artery were assessed semi-quantitatively by temperature measurements in the bench model. Lastly, a quantitative assessment was performed by 3D computational fluid dynamics, where the standard deviation and entropy ratio of the temperature over the cross-section in the coronary artery model were calculated for both catheters. All three evaluation methods demonstrated that the Rayflow catheter's specific design leads to a more optimal, homogeneous mixture of blood and saline over both the cross-section and length of a coronary vessel, as compared with the standard end-hole catheter.

Predicting capillary vessel network hemodynamics in silico by machine learning.

Blood velocity and red blood cell (RBC) distribution profiles in a capillary vessel cross-section in the microcirculation are generally complex and do not follow Poiseuille's parabolic or uniform pattern. Existing imaging techniques used to map large microvascular networks in vivo do not allow a direct measurement of full 3D velocity and RBC concentration profiles, although such information is needed for accurate evaluation of the physiological variables, such as the wall shear stress (WSS) and near-wall cell-free layer (CFL), that play critical roles in blood flow regulation, disease progression, angiogenesis, and hemostasis. Theoretical network flow models, often used for hemodynamic predictions in experimentally acquired images of the microvascular network, cannot provide the full 3D profiles either. In contrast, such information can be readily obtained from high-fidelity computational models that treat blood as a suspension of deformable RBCs. These models, however, are computationally expensive and not feasible for extension to the microvascular network at large spatial scales up to an organ level. To overcome such limitations, here we present machine learning (ML) models that bypass such expensive computations but provide highly accurate and full 3D profiles of the blood velocity, RBC concentration, WSS, and CFL in every vessel in the microvascular network. The ML models, which are based on artificial neural networks and convolution-based U-net models, predict hemodynamic quantities that compare very well against the true data but reduce the prediction time by several orders. This study therefore paves the way for ML to make detailed and accurate hemodynamic predictions in spatially large microvascular networks at an organ-scale.

Interrelation Between Cerebrospinal Fluid Pressure, Intracranial Morphology and Venous Hemodynamics Studied by 4D Flow MRI.

To quantify the effects of CSF pressure alterations on intracranial venous morphology and hemodynamics in idiopathic intracranial hypertension (IIH) and spontaneous intracranial hypotension (SIH) and assess reversibility when the underlying cause is resolved. We prospectively examined venous volume, intracranial venous blood flow and velocity, including optic nerve sheath diameter (ONSD) as anoninvasive surrogate of CSF pressure changes in 11 patients with IIH, 11 age-matched and sex-matched healthy controls and 9 SIH patients, before and after neurosurgical closure of spinal dural leaks. We applied multiparametric MRI including 4D flow MRI, time-of-flight (TOF) and T2-weighted half-Fourier acquisition single-shot turbo-spin echo (HASTE). Sinus volume overlapped between groups at baseline but decreased after treatment of intracranial hypotension (p = 0.067) along with asignificant increase of ONSD (p = 0.003). Blood flow in the middle and dorsal superior sagittal sinus was remarkably lower in patients with higher CSF pressure (i.e., IIH versus controls and SIH after CSF leak closure) but blood flow velocity was comparable cross-sectionally between groups and longitudinally in SIH. We were able to demonstrate the interaction of CSF pressure, venous volumetry, venous hemodynamics and ONSD using multiparametric brain MRI. Closure of CSF leaks in SIH patients resulted in symptoms suggestive of increased intracranial pressure and caused asubsequent decrease of intracranial venous volume and of blood flow within the superior sagittal sinus while ONSD increased. In contrast, blood flow parameters from 4D flow MRI did not discriminate IIH, SIH and controls as hemodynamics at baseline overlapped at most vessel cross-sections.

Evaluating the Impact of Domain Boundaries on Hemodynamics in Intracranial Aneurysms within the Circle of Willis

Hemodynamic simulations are increasingly used to study vascular diseases such as Intracranial Aneurysms (IA) and to further develop treatment options. However, due to limited data, certain aspects must rely on heuristics, especially at the simulation’s distal ends. In the literature, Murray’s Law is often used to model the outflow split based on vessel cross-section area; however, this poses challenges for the communicating arteries in the Circle of Willis (CoW). In this study, we contribute by assessing the impact of Murray’s Law in patient-specific geometries featuring IA at the posterior communication. We simulate different domain extensions representing common modelling choices and establish Full CoW simulations as a baseline to evaluate the effect of these modelling assumptions on hemodynamic indicators, focusing on IA growth and rupture-related factors such as the Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI). Our findings reveal qualitative alterations in hemodynamics when not modeling posterior communication. Comparisons between computing the anterior circulation and computing the whole Circle of Willis reveal that quantitative changes in WSS may reach up to 80%, highlighting the significance of modelling choices in assessing IA risks and treatment strategies.

Stress Analysis and Structural Improvement of LNG Tank Container Frames under Impact from Railway Transport Vehicles

As the stress of the frame, especially the bottom side rail supports and bottom inclined supports, of a traditional LNG tank container could be significantly greater than its allowable stress, and the container cannot meet the strength requirement of the specification when it is impacted by a transport vehicle during railway transportation, three improved frame structures were suggested, which removed or changed the side rails or bottom inclined supports; the stress and deformation of these improved frames and the tank container were analyzed using the finite element method under the impact test. The results show that all three improved frames can meet the strength requirement, i.e., the maximum Mises stress is less than the allowable stress and the deformation requirement of the diagonal length difference is less than the allowable value, meaning that the tank containers with improved frames can pass the impact test. Moreover, for the FRP support rings and impact side heads, although the maximum values are different, they are still less than the respective allowable stresses. In addition, the maximum value of the middle cross section of the outer vessel in the direction of gravity does not increase with the change in the frame, and the deformation of the outer vessel remains within the elastic range. Therefore, the improvements of the frames have little effect on the stress and deformation of the other components of the tank container, in particular, the inner vessel and outer vessel. Compared to the frame of the traditional tank container, removing the side rails partially or completely can reduce the weight of the frame by 17.99% and 38.34%, respectively, greatly reducing manufacturing and transportation costs. It can also reduce the maximum Mises stress by 38.89% and 39.24% and the maximum diagonal difference by 57.95% and 61.16%.

Registration between 2D and 3D Ultrasound Images to Track Liver Blood Vessel Movement.

For the accurate positioning of surgical tools, conventional intraoperative navigation systems have been developed to recognize the relationship between target positions and the tools. However, since an internal organ is deformed during the operation, registration between realtime two-dimensional (2D) ultrasound images and three-dimensional (3D) CT or MRI images is not always effective. Therefore, this study developed image registration between 2D and 3D ultrasound images considering deformation for tracking target vessel movement in the liver. 3D ultrasound image was obtained in advance with 3D coordinates, including the target vessel. Then real-time 2D images and ultrasound probe position were simultaneously acquired using a 3D position sensor. We applied multiple image resolution registration, where rapid and fine optimizations can be expected at higher and lower levels, respectively. Meanwhile, the gradient descent method was adopted for the optimization, which determines the relative arrangements to obtain maximum similarity between 2D and 3D images. We experimentally established resolution level parameters using a phantom before applying it to track liver blood vessel movements in a normal healthy subject. Comparing the 2D images and the registered images, although the approach has some limitations in tracking large displacement, we confirmed that the cross-section of the target blood vessel was clearly visualized. This method has the potential for an ultrasound therapy targeting blood vessels under natural respiration conditions.

Lymphatic ultrasound (D-CUPS) and multi-point ICG lymphography for successful LVA

Securing dilated lymphatic vessels with good function is challenging when performing lymphaticovenous anastomosis (LVA). To achieve this, we propose multi-point indocyanine green (ICG) lymphography and lymphatic ultrasound (D-CUPS; Doppler, Cross, Uncollapsible, Parallel, and Superficial fascia). With multi-point ICG lymphography, more lymphatic vessels can be found than with conventional ICG lymphography, which leads to better surgical results. Lymphatic ultrasound is more useful because it allows the observation of cross-sections of lymphatic vessels. It is known that lymphatic degeneration occurs in the lymphatic vessels in lymphedematous limbs, and LVA is most effective when dilated lymphatic vessels are anastomosed. The degree of lymphatic degeneration can be diagnosed with lymphatic ultrasound, and the proximity of dilated lymphatic vessels and veins suitable for anastomosis can be reliably identified and selected as the skin incision site for LVA. Lymphatic ultrasound is a safe, versatile and useful imaging technique that does not require a contrast agent and can be performed by anyone. By mastering multi-point ICG lymphography and lymphatic ultrasound (D-CUPS), the operation time can be shortened, and more effective LVA can be performed. In this Technical Note article, we comprehensively describe lymphatic function examinations that we have developed so far.

3D-shape formation of blood vessels based on computer aided design system

This paper proposes and tests a computerized approach for constructing a 3D model of blood vessels from angiogram images. The approach is divided into two steps, image features extraction and solid model formation. In the first step, image morphological operations and post-processing techniques are used for extracting geometrical entities from the angiogram image. These entities are the middle curve and outer edges of the blood vessel, which are then passed to a computer-aided graphical system for the second phase of processing. The system has embedded programming capabilities and pre-programmed libraries for automating a sequence of events that are exploited to create a solid model of the blood vessel. The gradient of the middle curve is adopted to steer the vessel’s direction, while the cross-sections of the blood vessel are formed as a sequence of circles lying in planes that are orthogonal to the gradients of the middle curves. The radii for the circles are estimated as a distance between the intersection points of the blood vessel edges with the orthogonal plane to the middle curve gradient. The system then uses these circles and the middle curve gradients to produce a solid volume that represents the 3D shape of the blood vessel. The method was tested and evaluated using different cases of angiogram images, and showed a reasonable agreement between the generated shapes and the tested images.

Reynolds number scaling and energy spectra in geostrophic convection.

We report flow measurements in rotating Rayleigh-Bénard convection in the rotationally-constrained geostrophic regime. We apply stereoscopic particle image velocimetry to measure the three components of velocity in a horizontal cross-section of a water-filled cylindrical convection vessel. At a constant, small Ekman number Ek = 5 × 10-8 we vary the Rayleigh number Ra between 1011 and 4 × 1012 to cover various subregimes observed in geostrophic convection. We also include one nonrotating experiment. The scaling of the velocity fluctuations (expressed as the Reynolds number Re) is compared to theoretical relations expressing balances of viscous-Archimedean-Coriolis (VAC) and Coriolis-inertial-Archimedean (CIA) forces. Based on our results we cannot decide which balance is most applicable here; both scaling relations match equally well. A comparison of the current data with several other literature datasets indicates a convergence towards diffusion-free scaling of velocity as Ek decreases. However, the use of confined domains leads at lower Ra to prominent convection in the wall mode near the sidewall. Kinetic energy spectra point at an overall flow organisation into a quadrupolar vortex filling the cross-section. This quadrupolar vortex is a quasi-two-dimensional feature; it only manifests in energy spectra based on the horizontal velocity components. At larger Ra the spectra reveal the development of a scaling range with exponent close to -5/3, the classical exponent for inertial-range scaling in three-dimensional turbulence. The steeper Re(Ra) scaling at low Ek and development of a scaling range in the energy spectra are distinct indicators that a fully developed, diffusion-free turbulent bulk flow state is approached, sketching clear perspectives for further investigation.

Novel tools for neuronal activity, vessel diameter and red blood cell velocity imaging

Healthy brain function requires a delicate balance between neural activity and local vascular dynamics. Perturbations to this balance, such as vessel diameter changes or fluctuations in red blood cell velocity, are thought to underlie a number of neurodegenerative and neurovascular diseases, including migraine, stroke, and epilepsy. Here, for the first time, we demonstrate high fidelity simultaneous acquisition of vascular and neural circuit dynamics in freely-moving animals using our newly developed nVue dual color miniscope. Our system enables simultaneous imaging of blood flow and neural activity in both superficial and deep-brain structures in awake, behaving rodents. By multiplexing two LEDs at up to 100hz, the nVue enables direct, real-time visualization of both hemodynamics and calcium activity in two channels. Additionally, we have augmented the Inscopix Data Processing Software package to capture time-varying estimates of vessel diameter and red blood cell (RBC) velocity in specific vessels. Vessel diameter is estimated as the full-width half maximum of a Lorentzian function fit to vessel cross-section, while RBC velocity is calculated based on time-lagged correlations between seed-pixels within individual regions of interest and all immediately neighboring pixels. Distances between correlation peaks are then plotted against time. Manual annotation of blood flow data was performed to establish a ground truth against which to validate the algorithm. The nVue blood flow imaging application offers a powerful, turn-key, multisystem workflow for simultaneously interrogating hemodynamics and neural circuit function in freely behaving animals which will profoundly expand the neurovascular coupling toolkit not only for basic and translational research but also for the development of novel preclinical therapeutics. Commercial This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 159: Vascularized 3D cancer organoid research platform using surface acoustic waves

Abstract Recently, organoids have been widely used in cancer research. However, cancer organoids have limitation in reflecting physicochemical microenvironments of tumor. In particular, vascular networks not only provide oxygen and nutrients to the tumor, but also play an important role as a channel through which drugs move in cancer. Vascularization occurs in an uncontrollable form and speed in conventional methods. Here, we regulate the directionality of the vascular bed using the surface acoustic waves(SAW) technology by which, vascular cells are locally aligned. Aligned cells exhibited an improved, cell-cell contact enhancing the vascular system maturation in a couple days. Organoids are constructed from gastric cancer patients with four molecular subtypes according to TCGA. Organoids were dissociated into a single cell to make a co-culture spheroid with HUVEC cells. Co-cultured spheroids were formed by adding fibronectin according to the characteristics of the patient sample. The SAW device is built with interdigitated transducer, NiNbO3 substrate, polydimethylsiloxane(PDMS) and coverglass. After putting co-culture spheroids and HUVEC cells mixed with fibrin gel into the device, patterning is performed using surface acoustic waves with shaking in EGM-2 media. After fixing the models, CD31 and F-actin are stained and imaged through immunofluorescent. Immunohistochemistry was performed to confirm the blood vessel cross section. The blood vessels patterned with SAW were well aligned in a straight line, and a lumen structure was formed in a couple days. When co-cultured spheroids were used compared to mono-cultured spheroids, the interaction with external HUVECs was improved, allowing for efficient vascular organism models. As evidence for this, it was confirmed that HUVEC inside the co-cultured spheroid and HUVEC outside were connected through interaction when PKH dyeing was done in a different color. We showed that blood vessels are formed faster and thicker in patterning models than in random models, and interactions with co-cultured spheroids are also high. Through immunofluorescent staining, we found that the number of vascular branches linked to spheroids was higher in the SAW model. In addition, in the H&E results, it was confirmed that the blood vessels were arranged in a line, and that differentiation occurred appropriately to form a tubular structure. In addition, the number of blood formed inside the spheroid was higher. Currently, this model is used to test anti-cancer efficacy using FGFR inhibitors and ramucirumab in FGFR2-amplified patient-derived organoids. An efficient vascularized 3D cancer organoid model was constructed using acoustic waves. Our vascularized 3D cancer organoid research platform will be applied for specific drug screening platform that directly aid the treatment of the specific patients with various drugs including chemoagents, targeted drugs, and immune checkpoints inhibitors. Citation Format: Hyoyoung Kim, Yunam Lee, Byungjun Kang, Un-Jung Yun, Yunjung Choi, So Hui Kim, Hyunki Kim, Hyungsuk Lee, Minkyu Jung. Vascularized 3D cancer organoid research platform using surface acoustic waves [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 159.

Ultrasound localization microscopy of the human kidney allograft on a clinical ultrasound scanner

Chronic kidney disease is a major medical problem, causing more than a million deaths each year worldwide. Peripheral kidney microvascular damage characterizes most chronic kidney diseases, yet noninvasive and quantitative diagnostic tools to measure this are lacking. Ultrasound Localization Microscopy (ULM) can assess tissue microvasculature with unprecedented resolution. Here, we optimized methods on 35 kidney transplants and studied the feasibility of ULM in seven human kidney allografts with a standard low frame rate ultrasound scanner to access microvascular damage. Interlobar, arcuate, cortical radial vessels, and part of the medullary organization were visible on ULM density maps. The medullary vasa recta can be seen but are not as clear as the cortical vessels. Acquisition parameters were derived from Contrast-Enhanced Ultrasound examinations by increasing the duration of the recorded clip at the same plane. ULM images were compared with Color Doppler, Advanced Dynamic Flow, and Superb Microvascular Imaging with a contrast agent. Despite some additional limitations due to movement and saturation artifacts, ULM identified vessels two to four times thinner compared with Doppler modes. The mean ULM smallest analyzable vessel cross section was 0.3 ± 0.2 mm in the seven patients. Additionally, ULM was able to provide quantitative information on blood velocities in the cortical area. Thus, this proof-of-concept study has shown ULM to be a promising imaging technique for qualitative and quantitative microvascular assessment. Imaging native kidneys in patients with kidney diseases will be needed to identify their ULM biomarkers.

Settling and spreading behaviour of particle clusters in quiescent liquids in confined vessels

Here we report experiments on particle cluster settling at high Reynolds number in quiescent liquid contained in a vessel. The particles were observed to spread at the vessel bottom surface in a near-circular annular shape after settling irrespective of the shape of the vessel cross-section and particle shape, size, and types. Effect of different parameters such as mass, type and aspect ratio of the particles, height, and viscosity of liquid was investigated on spreading behaviour. Formation of the hemispherical bottom cap of the cluster that bounces upon hitting the vessel bottom surface was found to be responsible for the final circular annular shape of the settled structure. Particle leakage from the cluster was seen in the form of a tail. In the liquid having viscosity beyond 100 cP, cluster breakage was observed that resulted in hindered settling and asymmetric shapes of finally settled particles. The observations are useful to understand the overall area over which settling and spreading of such clusters can be observed.

A machine learning approach for predicting descending thoracic aortic diameter.

To establish models for predicting descending thoracic aortic diameters and provide evidence for selecting the size of the stent graft for TBAD patients. A total of 200 candidates without severe deformation of aorta were included. CTA information was collected and 3D reconstructed. In the reconstructed CTA, a total of 12 cross-sections of peripheral vessels were made perpendicular to the axis of flow of the aorta. Parameters of the cross sections and basic clinical characteristics were used for prediction. The data was randomly split into the training set and the test set in an 8:2 ratio. To fully describe diameters of descending thoracic aorta, three predicted points were set based quadrisection, and a total of 12 models at three predicted points were established using four algorithms included linear regression (LR), support vector machine (SVM), Extra-Tree regression (ETR) and random forest regression (RFR). The performance of models was evaluated by mean square error (MSE) of the prediction value, and the ranking of feature importance was given by Shapley value. After modeling, prognosis of five TEVAR cases and stent oversizing were compared. We identified a series of parameters which affect the diameter of descending thoracic aorta, including age, hypertension, the area of proximal edge of superior mesenteric artery, etc. Among four predictive models, all the MSEs of SVM models at three different predicted position were less than 2 mm2, with approximately 90% predicted diameters error less than 2 mm in the test sets. In patients with dSINE, stent oversizing was about 3 mm, while only 1 mm in patients without complications. The predictive models established by machine learning revealed the relationship between basic characteristics and diameters of different segment of descending aorta, which help to provide evidence for selecting the matching distal size of the stent for TBAD patients, thereby reducing the incidence of TEVAR complications.

Can the transection plane be optimized inpancreatic resections?

According to current protocol, the separation of pancreatic head and body is performed at the level of superior mesenteric vein (SMV). Previous data indicate that the resection plane should be modified in portal annular pancreas. We presumed that the optimal line of pancreatic resections could also be different in other cases. Our aim is to simulate pancreatic resections in different planes and find the optimal resection line with the minimum number of cut vessels. 25 abdominal vascular corrosion casts were prepared, the aorta and the portal vein were cannulated. CT scans were taken on the casts, and specific planes were reconstructed simulating different resection lines. The total amount of cross sections of vessels were calculated in the different planes. In our series, the optimal plane is the SMV in 11/25, 2 cm left in 10/25, 1 cm left in 4/25, 1 cm right in 1/25 and 2 cm right in none of our cases. The group of left sided extension contain more than half of the cases. With left sided resections, the cut surface of the vessels may be lowered to even 29% compared to the SMV plane. Our study revealed that pancreatic resections should be extended to the left side of the SMV in more than half of our cases. Therefore, the resection plane should be determined by preoperative imaging methods. Using DICOM viewer with multiplanar reconstruction, the resection planes can be simulated in clinical practice, which would reduce the risk of postoperative bleeding.

Numerical Study of Supra-Wavelength Axial Motion Compensation in Contact-Mode Optical Coherence Angiography Using Fourier-Shift Procedures

Label-free angiographic methods based on optical coherence tomography (OCT) visualize blood vessels utilizing detection of red blood cells motion against surrounding static tissue. However, in practice, the surrounding tissue is never still due to natural motions of living organisms (e.g., breathing or heart beating). To mitigate large scale motions of the tissue relatively to the OCT probe the tissue examination can be made in contact mode. In such a case, however, the OCT probe inevitably exerts some pressure onto the tissue, so that bulk motions lead to interframe deformations and depth-dependent tissue displacements which have to be numerically compensated prior to angiographic visualization. Usually, sufficiently small deformations primarily affect pixel phases in OCT images rather than pixel amplitudes, and, therefore, phase-only compensation of the masking motions may be fairly sufficient. However, in case of larger strains and supra-wavelength displacements, larger inter-scan phase variations of the order of several periods lead to the appearance of pronounced “decorrelation noise” in which variations in pixel amplitudes and phases are combined. This effect significantly degrades the quality of the final OCT-angiography images. In this paper, we present a new method allowing to a significant degree to compensate this phase-amplitude decorrelation caused by spatially-inhomogeneous supra-wavelengths displacements. This compensation is based on the Fourier-shift theorem which allows one to back-shift fragments of the deformed OCT-scans to their initial positions before deformation. At the same time variations of pixels due to the motion of blood particles within smaller-in-size vessel cross sections are retained. Although such backshifts do not compensate relative motions of sub-resolution particles, this procedure efficiently reduces decorrelation even for fairly big spatially-inhomogeneous displacements and leads to much lower signal variability outside blood vessels while preserving high variability inside. The proposed compensation method is compared to the earlier proposed phase-only compensation using simulated data. Pronouncedly lower strain-induced artefacts and much higher contrast between blood vessels and background are demonstrated.

Atherosclerosis risk classification with computed tomography angiography: A radiologic-pathologic validation study

Background and aimsThe application of machine learning to assess plaque risk phenotypes on cardiovascular CT angiography (CTA) is an area of active investigation. Studies using accepted histologic definitions of plaque risk as ground truth for machine learning models are uncommon. The aim was to evaluate the accuracy of a machine-learning software for determining plaque risk phenotype as compared to expert pathologists (histologic ground truth). MethodsSections of atherosclerotic plaques paired with CTA were prospectively collected from patients undergoing carotid endarterectomy at two centers. Specimens were annotated for lipid-rich necrotic core, calcification, matrix, and intraplaque hemorrhage at 2 mm spacing and classified as minimal disease, stable plaque, or unstable plaque according to a modified American Heart Association histological definition. Phenotype is determined in two steps: plaque morphology is delineated according to histological tissue definitions, followed by a machine learning classifier. The performance in derivation and validation cohorts for plaque risk categorization and stenosis was compared to histologic ground truth at each matched cross-section. ResultsA total of 496 and 408 vessel cross-sections in the derivation and validation cohorts (from 30 and 23 patients, respectively). The software demonstrated excellent agreement in the validation cohort with histological ground truth plaque risk phenotypes with weighted kappa of 0.82 [0.78–0.86] and area under the receiver operating curve for correct identification of plaque type was 0.97 [0.96, 0.98], 0.95 [0.94, 0.97], 0.99 [0.99, 1.0] for unstable plaque, stable plaque, and minimal disease, respectively. Diameter stenosis correlated poorly to histologically defined plaque type; weighted kappa 0.25 in the validation cohort. ConclusionsA machine-learning software trained on histological ground-truth tissue inputs demonstrated high accuracy for identifying plaque stability phenotypes as compared to expert pathologists.