Hepatic Hemangiomas Alter Morphometry and Impair Hemodynamics of the Abdominal Aorta and Primary Branches From Computer Simulations

Deep learning-based hemodynamic prediction of carotid artery stenosis before and after surgical treatments

Hemodynamic prediction of carotid artery stenosis (CAS) is of great clinical significance in the diagnosis, prevention, and treatment prognosis of ischemic strokes. While computational fluid dynamics (CFD) is recognized as a useful tool, it shows a crucial issue that the high computational costs are usually required for real-time simulations of complex blood flows. Given the powerful feature-extraction capabilities, the deep learning (DL) methodology has a high potential to implement the mapping of anatomic geometries and CFD-driven flow fields, which enables accomplishing fast and accurate hemodynamic prediction for clinical applications. Based on a brain/neck CT angiography database of 280 subjects, image based three-dimensional CFD models of CAS were constructed through blood vessel extraction, computational domain meshing and setting of the pulsatile flow boundary conditions; a series of CFD simulations were undertaken. A DL strategy was proposed and accomplished in terms of point cloud datasets and a DL network with dual sampling-analysis channels. This enables multimode mapping to construct the image-based geometries of CAS while predicting CFD-based hemodynamics based on training and testing datasets. The CFD simulation was validated with the mass flow rates at two outlets reasonably agreed with the published results. Comprehensive analysis and error evaluation revealed that the DL strategy enables uncovering the association between transient blood flow characteristics and artery cavity geometric information before and after surgical treatments of CAS. Compared with other methods, our DL-based model trained with more clinical data can reduce the computational cost by 7,200 times, while still demonstrating good accuracy (error<12.5%) and flow visualization in predicting the two hemodynamic parameters. In addition, the DL-based predictions were in good agreement with CFD simulations in terms of mean velocity in the stenotic region for both the preoperative and postoperative datasets. This study points to the capability and significance of the DL-based fast and accurate hemodynamic prediction of preoperative and postoperative CAS. For accomplishing real-time monitoring of surgical treatments, further improvements in the prediction accuracy and flexibility may be conducted by utilizing larger datasets with specific real surgical events such as stent intervention, adopting personalized boundary conditions, and optimizing the DL network.

Influence of MRI-based boundary conditions on type B aortic dissection simulations in false lumen with or without abdominal aorta involvement

Most computational hemodynamic studies of aortic dissections rely on idealized or general boundary conditions. However, numerical simulations that ignore the characteristics of the abdominal branch arteries may not be conducive to accurately observing the hemodynamic changes below the branch arteries. In the present study, two men (M-I and M-II) with type B aortic dissection (TBAD) underwent arterial-phase computed tomography angiography and four-dimensional flow magnetic resonance imaging (MRI) before and after thoracic endovascular aortic repair (TEVAR). The finite element method was used to simulate the computational fluid dynamic parameters of TBAD [false lumen (FL) with or without visceral artery involvement] under MRI-specific and three idealized boundary conditions in one cardiac cycle. Compared to the results of zero pressure and outflow boundary conditions, the simulations with MRI boundary conditions were closer to the initial MRI data. The pressure difference between true lumen and FL after TEVAR under the other three boundary conditions was lower than that of the MRI-specific results. The results of the outflow boundary conditions could not characterize the effect of the increased wall pressure near the left renal artery caused by the impact of Tear-1, which raised concerns about the distal organ and limb perfused by FL. After TEVAR, the flow velocity and wall pressure in the FL and the distribution areas of high time average wall shear stress and oscillating shear index were reduced. The difference between the calculation results for different boundary conditions was lower in M-II, wherein FL did not involve the abdominal aorta branches than in M-I. The boundary conditions of the abdominal branch arteries from MRI data might be valuable in elucidating the hemodynamic changes of the descending aorta in TBAD patients before and after treatment, especially those with FL involving the branch arteries.

Self-Similar Functional Circuit Models of Arteries and Deterministic Fractal Operators: Theoretical Revelation for Biomimetic Materials

In this paper, the self-similar functional circuit models of arteries are proposed for bioinspired hemodynamic materials design. Based on the mechanical-electrical analogous method, the circuit model can be utilized to mimic the blood flow of arteries. The theoretical mechanism to quantitatively simulate realistic blood flow is developed by establishing a fractal circuit network with an infinite number of electrical components. We have found that the fractal admittance operator obtained from the minimum repeating unit of the fractal circuit can simply and directly determine the blood-flow regulation mechanism. Furthermore, according to the operator algebra, the fractal admittance operator on the aorta can be represented by Gaussian-type convolution kernel function. Similarly, the arteriolar operator can be described by Bessel-type function. Moreover, by the self-similar assembly pattern of the proposed model, biomimetic materials which contain self-similar circuits can be designed to mimic physiological or pathological states of blood flow. Studies show that the self-similar functional circuit model can efficiently describe the blood flow and provide an available and convenient structural theoretical revelation for the preparation of in vitro hemodynamic bionic materials.

Morphological and hemodynamic analysis of the patient-specific renal cell carcinoma models

Although the morbidity of renal cell carcinoma (RCC) has been increasing as the seventh most common tumours, to our knowledge, there is few studies foucsing on the hemodynamics of the renal artery (RA) with RCC. The objective of this study is to perform morphological and hemodynamic analysis of the RA and abdominal aorta artery (AAA) in the control healthy and RCC patient groups. Three-dimensional (3D) geometries are reconstructed from 18 control healthy subjects and 15 RCC patients based on Computed Tomography Angiography (CTA) images. There is higer in the lumen diameter of the RA (6.21 ± 0.89 mm) and curvature of the RA (1.2 ± 0.07) in the RCC patient group compared with the control healthy group (4.29 ± 1.08 mm, 1.1 ± 0.1), respectively. In the hemodynamic analysis, the surface area ratio (%) of low time-averaged wall shear stress (SAR-TAWSS) at the RA (10.65 ± 11.65) and AAA (48.49 ± 12.79) in the RCC patient group is significantly higher than that in the control healthy group (0.23 ± 0.22, 21.57 ± 20.5), respectively. It is found that RCC altered the morphology of the RA in the RCC patient group, which could deteriorate the hemodynamic environment of the RA and AAA. The finding in this study could enhance us to understand the progression of vascular disease caused by RCC.

A highly parallel simulation of patient-specific hepatic flows

Computational hemodynamics is being developed as an alternative approach for assisting clinical diagnosis and treatment planning for liver diseases. The technology is non-invasive, but the computational time could be high when the full geometry of the blood vessels is taken into account. Existing approaches use either one-dimensional model of the artery or simplified three-dimensional tubular geometry in order to reduce the computational time, but the accuracy is sometime compromised, for example, when simulating blood flows in arteries with plaque. In this work, we study a highly parallel method for the transient incompressible Navier-Stokes equations for the simulation of the blood flows in the full three-dimensional patient-specific hepatic artery, portal vein and hepatic vein. As applications, we also simulate the flow in a patient with hepatectomy and calculate the S (PPG). One of the advantages of simulating blood flows in all hepatic vessels is that it provides a direct estimate of the PPG, which is a gold standard value to assess the portal hypertension. Moreover, the robustness and scalability of the algorithm are also investigated. A 83% parallel efficiency is achieved for solving a problem with 7 million elements on a supercomputer with more than 1000 processor cores.

Natural history of hepatic hemangiomas as a guide for surgical indication

Background

Generally, hemangiomas are asymptomatic and most lesions are incidentally diagnosed on abdominal ultrasonography. The indications for surgery are still debated mainly due to limited data about the natural history of hepatic hemangiomas. The aim of this study is to investigate the natural history of hepatic hemangiomas, the effects of age and sex on their growth, and their tendency to increase in size or causing symptoms or complications as a guide for surgical indication. In this current study, combined retrospective and prospective analysis was conducted on 186 Egyptian adult patients having 244 hepatic hemangiomas who attended to the outpatient clinics. Follow-up was performed to observe the accurate site, size, number, rate of growth of the lesions, and their tendency to cause symptoms or complications.

Results

Ninety-one percent of patients were asymptomatic and 9% were symptomatic. During follow-up, 48% of patients showed an increase in tumor diameter, 22% decreased, and 30% were stable. The growth rate at 18–45-year group showed an increasing trend that was higher in females; it was 3.3 ± 2 mm/year for males and 3.9 ± 1.8 mm/year for females. At ˃ 45 year group, the female patients showed a decreasing trend (− 2.1 ± 1.1 mm/year) while in males showed an increasing trend that was slower than in 18–45-year group (2.6 ± 1.7 mm/year).

Conclusion

Growth pattern of liver hemangiomas is affected by age and sex. The majority of hemangiomas are asymptomatic and complications are rare. Hemangioma size alone is not an indication for surgery in asymptomatic patients. Surgical indications are limited to patients with severe symptoms, complications, or suspicious lesions. Most hemangiomas can be managed conservatively even giant hemangiomas.

Molecular and Functional Study of Transient Receptor Potential Vanilloid 1-4 at the Rat and Human Blood-Brain Barrier Reveals Interspecies Differences

Transient receptor potential vanilloid 1-4 (TRPV1-4) expression and functionality were investigated in brain microvessel endothelial cells (BMEC) forming the blood-brain barrier (BBB) from rat and human origins. In rat, Trpv1-4 were detected by qRT-PCR in the brain cortex, brain microvessels, and in primary cultures of brain microvessel endothelial cells [rat brain microvessel endothelial cells (rPBMEC)]. A similar Trpv1-4 expression profile in isolated brain microvessels and rPBMEC was found with the following order: Trpv4 > Trpv2 > Trpv3 > Trpv1. In human, TRPV1-4 were detected in the BBB cell line human cerebral microvessel endothelial cells D3 cells (hCMEC/D3) and in primary cultures of BMEC isolated from human adult and children brain resections [human brain microvascular endothelial cells (hPBMEC)], showing a similar TRPV1-4 expression profile in both hCMEC/D3 cells and hPBMECs as follow: TRPV2 > > TRPV4 > TRPV1 > TRPV3. Western blotting and immunofluorescence experiments confirmed that TRPV2 and TRPV4 are the most expressed TRPV isoforms in hCMEC/D3 cells with a clear staining at the plasma membrane. A fluorescent dye Fluo-4 AM ester was applied to record intracellular Ca2+ levels. TRPV4 functional activity was demonstrated in mediating Ca2+ influx under stimulation with the specific agonist GSK1016790A (ranging from 3 to 1000 nM, EC50 of 16.2 ± 4.5 nM), which was inhibited by the specific TRPV4 antagonist, RN1734 (30 μM). In contrast, TRPV1 was slightly activated in hCMEC/D3 cells as shown by the weak Ca2+ influx induced by capsaicin at a high concentration (3 μM), a highly potent and specific TRPV1 agonist. Heat-induced Ca2+ influx was not altered by co-treatment with a selective potent TRPV1 antagonist capsazepine (20 μM), in agreement with the low expression of TRPV1 as assessed by qRT-PCR. Our present study reveals an interspecies difference between Rat and Human. Functional contributions of TRPV1-4 subtype expression were not identical in rat and human tissues reflective of BBB integrity. TRPV2 was predominant in the human whereas TRPV4 had a larger role in the rat. This interspecies difference from a gene expression point of view should be taken into consideration when modulators of TRPV2 or TRPV4 are investigated in rat models of brain disorders.

Mechanical difference of left ventricle between rabbits of myocardial infarction and hypertrophy

The analysis of cardiac wall stress is of importance to understand the development of heart failure (HF). The aim of the study is to carry out the cardiac mechanics analysis to show the changes of left ventricular (LV) wall stresses after LV hypertrophy (LVH) and myocardial infarction (MI). Here, LVH and MI were generated in rabbit hearts through the transverse aortic constriction (TAC) and the distal left circumflex (LCx) artery ligation operations, respectively. Physiological and CT measurements were carried out at postoperative 2 and 4 weeks, based on which a finite element (FE) model was developed to perform the mechanics computation. We found a gradual increase of end-diastolic myofiber stress in free wall and interventricular septum of LVH and MI (higher stress in the free wall than the septum). In the interventricular septum, the 4-weeks LVH group has the highest ED myofiber stresses (11.378 ± 3.022 kPa), while the 4-weeks MI group has the highest ED myofiber stresses (13.494 ± 2.835 kPa) in the free wall. LVH increased myocardial volume (3.49 ± 0.07 and 4.52 ± 0.26 ml at postoperative 2 and 4 weeks) while MI increased LV volume (from 2.75 ± 0.29 to 4.19 ± 0.27 ml). LVH and MI had different distributions of local myofiber stress.