The challenges of imaging based computational fluid dynamics.

Objective To establish canine vertebral-basilar artery aneurysm models and evaluate hemodynamics in the models.Methods Partially anastomose right common carotid artery (CCA) and left CCA (end to side anastomosis) to create inverted Y-junction of arteries,and then suture a harvested segment of external jugular vein to the notch of anastomosis to create a vertebral-basilar artery aneurysm.These animals were examined by using 3D digital subtraction angiography 4 weeks after surgery.Geometry parameters of the aneurysm and surrounding vasculature,specific double inlet profiles were analyzed by simulation of computational fluid dynamics (CFD) on these animal models.Results All 9 aneurysm models were created successfully.Completely patency was observed in 8 cases,partial patency in 1 case.The aneurysm height was (8.83 ±2.61) mm,the width was (5.62±1.38) mm,the neck width was (3.92 ±1.68)mm,and the AR was 1.98 ± 0.53.Geometric and hemodynamic environments created in vertebral-basilar artery aneurysm models are similar to those reported for human vertebrobasilar junction aneurysms.Conclu-sion This study documents possibility and feasibility of creating vertebral-basilar artery aneurysm models in the canine.This model may be useful in preclinical studies targeting various complex vertebral vertebralbasilar artery aneurysm. Key words: Aneurysm; Model, animal; Canine; Hemodynamics

Objective To investigate the in vivo morphological change of hybrid vascular graft made of porcine fibrin and microprocessed SPU film under the hemodynamic condition for predetermined period of time. Methods Autologous vascular endothelial cells derived from the saphenous veins of 6 adult mongrel dogs were cultured and proliferated in vitro in M199 culture medium, prelined on the luminal surface of lyophilized porcine fibrin tube wrapped with a SPU thin film with multiple micropores as a compliant scaffold. After canine common carotid arteries were bilaterally replaced with these vascular grafts for 4 weeks, light and electron microscopy, radiological imaging examination and immunohistochemistry were performed to evaluate the patency and remodeling in vivo. Results Eight of 10 engineered vascular grafts were patent ( patency rate 80% ). The patent grafts possessed thin, smooth and glistening luminal surfaces at the predetermined observation period up to 4 weeks. The intimal layer was covered with confluent, cobblestone-like monolayered cells that were positively stained with factor Ⅷ-related antigen. The thickness of the neoarterial walls was about 900 μm at 4th week after implantation. Vascular medial tissue rich in smooth muscle cells in the hierarchic structures of arterial wall was observed, and more interestingly, mass of elastic fiber was found in the medial tissue as early as 4 weeks postoperatively. Conclusion The endothelialized hybrid vascular grafts can be transformed to similar hierarchic structures of arterial walls under the hemodynamic condition for as early as 4 weeks. Key words: Tissue engineering; Blood vessel; Fibrin; Transplantation

Objective To investigate the relationship between carotid artery plaque formation and blood pressure(BP),pulse pressure(PP),mean blood pressure(MBP) in elderly men.Methods A total of 1461elderly men were divided into carotid artery plaque group(n =1012)and non-carotid artery plaque group(n =449) according to vascular ultrasound examination.Systolic blood pressure(SBP) and diastolic blood pressure(DBP) were recorded by 24-hour ambulatory blood pressure monitoring(ABPM),at the same time pulse pressure (PP)and mean arterial blood pressure(MBP)were calculated.The relationship between carotid artery plaque formation and SBP,DBP,PP,MBP were analyzed.Results The age in carotid artery plaque group was significantly higher than that in non-carotid artery plaque group[(80.5±5.4) years old vs(77.3±5.9) years old,t =-4.233,P ＜ 0.01];The levels of SBP,PP and M BP in artery plaque group were significantly higher than those in non-carotid artery plaque group[SBP:(132.2±17.0) mm Hg vs(127.5±16.0) mm Hg,t =-4.893,P ＜ 0.001; PP:(60.8±13.4) mm Hg vs(55.9±12.5) mm Hg,t =-5.021,P ＜0.001) ;MBP:(92.6±10.3)mm Hg vs(91.0±9.9)mm Hg,t =-3.897,P ＜ 0.01].The incidence of carotid artery plaque was closely related to age(OR =1.061,P =0.0001),myocardial infarction(OR =1.896,P =0.0135),hypertension grades(OR =1.177,P =0.0019),high cholesterol(OR =1.353,P =0.0335),reduced systolic function(OR =2.466,P =0.0001),lower extremity arterial plaque(OR =5.453,P =0.0001).Conclusion In elderly men,formation of the carotid artery plaque is closely related to increased SBP,PP and MBP,but independent to DBP. Key words: Systolic blood pressure; Diastolic blood pressure; Pulse pressure; Mean bloodpressure; Carotid artery plaque

Objective To evaluate the clinical value of the color Doppler ultrasound for cerebral infarction in patients with extracranial carotid artery and vertebral artery. Methods Ninty-one cases of cerebral infarction patients in the hospital were examined of extracranial internal carotid artery, vertebral artery by color Doppler ultrasound. The pathological change patterns of arterial wall and the inner diameter of the arterial lumens and the peak flow rate (PSV), resistent index (RI)of the vertebral artery were observed.Results In the 91 cases of cerebral infarction patients, the inner diameter of carotid artery beyond the normal range, there were 17 cases in the left, 22 cases in the right.The most plaqueslie in carotid artery.The type of plaques was flat applanation spot at most, following was hard spot.Vertebral artery's peak flow rate was usually reduce, 52 cases in left, 57 cases in right. 22 patients' resistent index beyond the normal range in the left, and 36 cases in right.Conclusions The color Doppler ultrasound to extracranial carotid artery and vertebral artery provides the morphology and hemodynamics's change, offers important messages for the clinical diagnosis and treatment in the cerebral infarction. Key words: Cerebral infarction ; Extracranial carotid artery and vertebral artery ; Ultrasonograph ;

Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition. Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

Objective To explore the impact of arterial injury on distal limb blood supply in lower limb trauma. Methods Retrospective analysis of 93 patients with different levels of lower limb arterial injury admitted to our hospital from June 2014 to August 2017. There were 84 males and 9 females aged 43.54±9.90 years (ranging 25-65 years). Revascularization was performed through open reduction. Patients were divided into three groups according to their arterial injury locations. Proximal vessels were along the superficial femoral artery, from its beginning to the point where it was divided into the descending genicular artery and direct periosteal branches. Intermediate vessels were from the dividing point on the superficial femoral artery to the popliteal artery before it was divided into the medial inferior genicular artery. Distal vessels were from the dividing point on the popliteal artery to the distal end of the peroneal artery. The duration from injury to revascularization in the three groups were 13.67±5.99 h, 11.15±4.43 h, and 11.92±5.48 h, respectively. There was no significant difference between groups (F=1.564, P=0.215). ISS in the three groups were 13.00±3.74, 12.77±3.81, and 11.50±3.99, respectively. There was no significant difference between groups (F=1.445, P=0.241). The following items were compared among the three groups, postoperative creatine kinase, arterial blood lactate and limb compartment cut. Results Creatine kinase of the intermediate vascular group was 8 743.15±6 968.48 u/L, proximal vascular group 1 467.67±1 810.27 u/L, distal vascular group 2 893.51±1 304.56 u/L. The data of intermediate vascular group were higher than those of proximal and distal vascular groups with significant difference among the groups (F=22.587, P=0.000). The lactate of the intermediate vascular group was 3.20±1.51 mmol/L, proximal vascular group 1.63±0.46 mmol/L, distal vascular group 1.85±0.69 mmol/L with significant difference among the groups (F=20.612, P=0.000). The compartment cut of the intermediate vascular group was incised in 24, but not in 15. The proximal vascular group was not incised in 18, while 15 was incised and 21 not incised in distal vascular group. The rates of compartment cut were 61.5%, 0 and 41.7%, respectively with significant differences (χ2=19.156, P=0.000). Conclusion In lower limb injuries, the intermediate vascular (from the superficial femoral artery after it is divided into the descending genicular artery and direct periosteal branches to the popliteal artery before it is divided into the medial inferior genicular artery) injury leads to the most severe distal limb ischemia. Key words: Vascular system injuries; Wounds and injuries; Vascular grafting

Velocity vector comparison between vector flow imaging and computational fluid dynamics in the carotid bifurcation

Urban environmental problem became one of major issues during its urbanization processes. Environmental impacts are assessed during recent urban planning and development. Though the environmental impact assessment considers meteorological impact as a minor component, changes in wind environment during development can largely affect the distribution pattern of air temperature, humidity, and pollutants. Impact assessment of local wind is, therefore, a major element for impact assessment prior to any other meteorological impact assessment. Computational Fluid Dynamics (CFD) models are utilized in various fields such as in wind field assessment during a construction of a new building and in post analysis of a fire event over a mountain. CFD models require specially formatted input data and produce specific output files, which can be analyzed using special programs. CFD's huge requirement in computing power is another hurdle in practical use. In this study, a CFD model and related software processors were automated and integrated as a microscale wind environmental impact assessment system. A supercomputer system was used to reduce the running hours of the model. Input data processor ingests development plans in CAD or GIS formatted files and produces input data files for the CFD model. Output data processor produces various analytical graphs upon user requests. The system was used in assessing the impacts of a new building near an observatory on wind fields and showed the changes by the construction visually and quantitatively. The microscale wind assessment system will evolve, of course, incorporating new improvement of the models and processors. Nevertheless the framework suggested here can be utilized as a basic system for the assessment.

Hemodynamics have crucial role in the control of vascular tone, in the regulation of arterial remodeling, and in the production of mediators that maintain arterial function. Changes in hemodynamics forces induce profound alterations in vascular cell metabolism and function, in the extracellular matrix, and in smooth muscle cell (SMC) phenotypes, all being part of vessel wall remodeling. Vessel wall remodeling plays a key role in arterial wall homeostasis but also in the initiation and development of arterial disease. This aim of this work is to study the effects of two distinct biomechanical stimuli, oscillatory shear and cyclic stretch on vessel wall function. Our 71 investigation is performed using an improved in vitro artery perfusion system, which allows to study the exact contribution of each biomechanical stimulus on isolated arterial segments, where the biological cell responses of endothelial and SMCs, and the extracellular matrix interactions are well preserved. The present thesis is divided into two main sections. The first part focuses on the effects of oscillatory shear stress on arterial segments, a mechanism presumed to be involved in the localization and initiation of atherosclerotic plaques. The second section investigates the influence of reduced cyclic stretch on the arterial wall, a procedure that is occurring in arterial stiffening. In the first and second papers, we examined the effects of three different shear stress conditions on the endothelium, SMC, and arterial wall responses, in porcine carotid arteries perfused in vitro for three days. We demonstrated that oscillatory shear stress, which is usually present in plaque-prone areas, decreased the bradykinin-induced vasorelaxation after 3 days of perfusion. The endothelial dysfunction was correlated to an impaired endothelial nitric oxide synthase gene expression and bradykinin-mediated activation. The potential lack of nitric oxide production and/or bioavailability observed in arteries exposed to oscillatory shear stress may also be the cause of the start of matrix turnover. Expression and activation of matrix metalloproteinase-2 and-9 were increased in arteries exposed to oscillatory shear, suggesting that this type of shear stress triggers a remodeling process. This part of the study provides a new insights on the role of shear stress in the control of arterial function and supports the hypothesis that oscillatory shear stress is a determining factor predisposing the arterial wall to atherosclerosis. The third paper focuses on the effects of cyclic stretch on vascular smooth muscle function, phenotype and wall remodeling. Arteries were wrapped by an external banding, which drastically decreased compliance and therefore the cyclic stretch. Arteries were perfused for one day under a unidirectional shear stress (6±3 dyn/cm2) in combination with a mean pressure of 80 mmHg and a pulse pressure of +/-10 mmHg. We demonstrated that exposure to reduced cyclic stretch induced a rapid modulation of SMC phenotype which was combined with a decrease in norepinephrine-induced vasocontraction. SMC dedifferentiation was associated to a decrease of plasminogen activator inhibitor-1 expression, which, combined with enhanced matrix metalloproteinase-2, may promote wall remodeling and SMC migration. These findings give a further approach into possible consequences of an arterial stiffening on large vessel wall patho-physiology.

Objective To investigate the probability and clinical significance of carotid and vertebral atherosclerotic plaque in patients with diabetes mellitus (DM). Methods From September 2012 to September 2017, 465 patients with DM in Taiyuan Central Group Hospital were examined by color Doppler ultrasound.The incidence of carotid plaque, vertebral artery plaque was analyzed, logistic regression analysis was used to analyze the risk factors of atherosclerosis formation and adverse outcomes in DM patients. Results There were 351 cases of arterial plaques, the detection rate was 75.48%, including 69.23% of carotid arteries, 60.97% of vertebral arteries, 61-70 years old accounted for 93.65%, patients with fasting blood glucose >15.0 mmol/L accounted for 79.17%, DM patients with the course of more than 10 years accounted for 97.80% of detectable arterial plaque.The age, fasting blood glucose level, duration had statistically significant differences between the plaque group and non plaque group (F=10.564, 9.165, 10.285, all P 2points were risk factors of poor prognosis of DM patients, the OR values were 3.592 (95% CI: 0.956~6.261), 2.913 (95% CI: 1.238~9.238). Conclusion Patients with DM has a higher risk of carotid artery and vertebral artery plaque, the higher the blood sugar level, the higher the plaque score, the worse the prognosis. Key words: Diabetes mellitus; Carotid arteries; Vertebral artery; Arteriosclerosis

Vascular remodeling is defined as any enduring change in the size and composition of an adult blood vessel, allowing adaptation or repair. The vascular remodeling response has been shown to depend on a variety of endogenous and environmental factors. Physiological remodeling is a tightly regulated process that mainly occurs in response to long-term changes in hemodynamic conditions. The adaptation to these hemodynamic changes implies the production of mediators that influence structure as well as function. A loss of regulation in the adaptive response underlies the pathogenesis of major cardiovascular diseases, including hypertension, atherosclerosis, restenosis and arterial aneurismal dilatation. Specialized enzymes called matrix metalloproteinases (MMPs) have been shown to have a predominant participation in the reorganization of the vessel structure, through the degradation of the extracellular matrix scaffold. The aim of this thesis is to gain insight in the biological and mechanical processes taking place in the vascular wall as an adaptive response to different biomechanical stimuli such as blood pressure and blood flow. This work proposes a new model for the study of vascular remodeling where physical factors acting on the arterial wall can be dissociated and analyzed, individually, in relation to the biological response. The results are presented in form of an introduction, three scientific papers and a conclusion section. The investigation has been designed around three different approaches: adaptation of a non-uniform artery to an in vitro environment, vascular adaptation to steady and pulsatile pressure and vascular adaptation to unidirectional and oscillatory flow. The adaptive response to each one of the variables chosen has been analyzed through biological and biomechanical remodeling indicators of the arterial wall. The introduction is an overview of the biological and biomechanical characteristics of arterial wall in relation to the remodeling process. The contribution of vascular smooth muscle cells and extracellular matrix to physiological and pathological arterial remodeling is discussed. Paper I assesses the relative remodeling of a non-axisymmetric artery in relation to its environment. The study considers the native circumferential asymmetry of the porcine right common carotid, which results from the non-homogenous mechanical and hemodynamic native environment. The adaptive response of the artery to an in vitro perfusion environment is analyzed. The study shows that in vitro perfusion leads, through remodeling, to a circumferentially uniform scleroprotein distribution and to a change in arterial compliance. This study emphasizes the link between structural changes, the biomechanical response and the enzymatic implication in the adaptive response. In paper II we investigate the role of continuous and cyclic stretch, produced by steady or pulsatile pressure acting on the arterial wall, on the remodeling response. The study shows that exposure to continuous and cyclic stretch differentially affects the relative scleroprotein content and leads to a change in arterial wall stiffness. The adaptive outcome is studied through an integrative approach taking into consideration the geometrical and structural adaptation, the biomechanical behavior and the enzymatic agents implicated in extracellular matrix turnover. Paper III analyzes the influence of different flow patterns on the arterial adaptive response. We investigate the differential effects of oscillatory flow, mimicking a plaque-prone hemodynamic environment, and unidirectional flow, to mimicking a physiologically protective (plaquefree) environment. The effect of these hemodynamic forces on the remodeling response are characterized through the study of endothelial and smooth muscle cell function as well as through assessment of agents influencing extracellular matrix turnover. The conclusions section presents a synthesis of the results and contribution of this thesis and proposes perspectives for future studies.

Objective To investigate the correlation of large artery stenosis and early neurological deterioration (END) of middle cerebral artery infarction. Methods The patients with middle cerebral artery infarction were enrolled retrospectively. END was defined as that the National Institutes of Health Stroke Scale (NIHSS) scores increased ≥2 within 72 hours of admission compared with the baseline value. Middle cerebral artery and internal carotid artery were evaluated by using cerebral angiography. The degree of stenosis was divided into 4 grades: non- or mild (<50%), moderate (50-70%), severe (71-99%) stenosis, and occlusion (100%). The clinical risk factors, degree of neurological deficits, size of lesion, and major arterial lesions were compared between the END group and the non-END group. Results A total of 256 patients with middle cerebral artery infarction were enrolled, and END occurred in 70 of them (27.34%). The age (P=0.045), infarct volume (P=0.045), baseline NIHSS score (P=0.007), and major arterial stenosis (P=0.038) of the END positive group were significantly higher or lager than those of the END negative group. Multivariate logistic regression analysis showed that the higher baseline NIHSS score (odds ratio [OR] 1.071, 95% confidence interval [CI] 1.004-1.142; P=0.037), infarction diameter >20 mm (OR 2.077, 95% CI 1.077-3.736; P=0.028), and severe stenosis of the major artery (OR 2.521, 95% CI 1.079-5.886; P=0.033) or occlusion (OR 3.074, 95% CI1.262-7.489; P=0.013) were the independent predictor of END. Conclusions Severe stenosis or occlusion of the major artery may be an independent predictor of END in patients with middle cerebral artery infarction. Key words: Stroke; Brain Ischemia; Disease Progression; Intracranial Arteriosclerosis; Cerebral Angiography; Middle Cerebral Artery; Carotid Stenosis; Risk Factors; Time Factors

Objective To study the relationship and predictive value of variation of carotid artery elasticity detected by echotracking (ET) technique and aortic valve calcification detected by two - dimensional ultrasonography with coronary heart disease (CHD). Methods The carotid artery elasticity of 196 cases who underwent coronary angiography(CAG) for suspected CHD were detected by echotracking (ET) technique and the indicators of artery elasticity were recorded, which includes elasticity modulus ( Ep), stiffness parameter ( β ), arterial compliance ( AC ) and pulse wave velocity ( PWVβ ).And aortic valve calcification was detected by two - dimensional ultrasonography, T test was carried out between the results of ultrasound examination and CAG. Results The indicators β, EP of carotid artery elasticity were positively correlated with the extent of CHD( r =0. 281,0.253; P ＜ 0.01, ＜ 0.05). In the mean time, positive correlation between aortic valve calcification and the extent of CHD was found (r = 0. 173, P ＜ 0.05). Conclusions Carotid artery elasticity reducing and AVC are high risk factors of CHD and have great values in predicting CHD. Key words: Ultrasonography ; Echotracking technique ; Artery elasticity ; Aortic valve calcification ; Coronary heart disease ;

Objective To explore neointimal hyperplasia in small-caliber decellularized matrix vascular grafts at 4 weeks after transplantation.Methods 17 male dogs were randomly divided into 2 groups.All the animals underwent right common carotid artery interposition with DCM (n =9) or ePTFE (n =8) vascular grafts.Color Doppler Ultrasound was applied to detect peak systolic velocity (PSV),end diastolic velocity (EDV),resistance index (RI),and inner diameter of anastomosis and midportion of the grafts at 1 and 4 weeks after implantation.All the grafts were harvested and evaluated by HE staining and light microscopy.Results All implanted grafts remained patent within 4 weeks.The difference of RI (△ RI) at the distal anastomosis between 1 and 4 weeks differed significantly in the two groups (P＜0.05).The difference of other hemodynamic parameters at anastomosis and midportion of the grafts did not differ significantly between the two groups (P＞0.05 for all comparisons).The difference of inner diameter (△ D) at anastomosis and midportion was significantly smaller in DCM group than in ePTFE group (P＜0.05 for all comparisons).Conclusions The degree of neointimal hyperplasia is smaller in small-caliber DCM vascular grafts than in ePTFE vascular grafts within 4 weeks after ttransplantation. Key words: Small-caliber, Vascular grafts; Decellularized matrix; ePTFE; Color Doppler ultrasound

Objective To explore the efficacy and safety of arterial embolectomy with Solitaire AB stent in treatment of acute intracranial large artery occlusion.Methods The clinical data of 11 patients with acute intracranial large artery occlusion receiving arterial embolectomy with Solitaire AB stent from March to December 2013 were analyzed retrospectively.Among them,5 cases were with simple middle cerebral artery occlusion,1 case combined with occlusion in the intracranial part of the internal carotid artery,4 cases had simple basilar artery occlusion,and 1 case had occlusion in the intracranial portion of the vertebral arteries extending to intracranial portion of the basilar artery.Revascularization and postoperative hemorrhage were analyzed,and nosocomial as well as clinical outcomes after 3 months were evaluated.Results Ten patients showed successful revascularization,of which 8 cases reached the standard of perfect revascularization.After embolectomy,there was obvious stenosis in offending vessel of 4 cases,who were given balloon dilatation then.In 3 cases,the vessels were still narrow,so Solitaire AB stent was placed in the stenosis area to correct stenosis with the residual stenosis rate of less than 40％.Thus electrolytic interruption was given.There was no symptomatic intracranial hemorrhage.Three months after the operation,5 cases recovered,among whom 2 cases had obvious curative effect instantly,1 case had complete remissions in 1 week,and 1 case remained hemiplegia.Five cases died,and 4 cases discharged from the hospital because their family gave up the subsequent treatment.Conclusions Arterial embolectomy with Solitaire AB stent to treat patients with acute intracranial large artery occlusion has a relatively higher revascularization rate.The clinical outcome after 3 months can be significantly improved.Thus,it provides a safe and effective endovascular treatment for patients with acute intracranial large artery occlusion. Key words: Arterial occlusive diseases; Brain infarction; Intracranial large artery; Solitaire AB stent