DSA-based Quantitative Evaluation Of Carotid Artery Perfusion And Hemodynamic Studies

Digital subtraction angiography(DSA)is the "gold standard" in the evaluation of vascular stenosis and plays a very important role in the diagnosis and interventional treatment of cardiovascular and cerebrovascular diseases.However,at present,only the anatomic imaging function of DSA has been paid attention to in clinical practice,but the role of DSA in evaluating cerebral perfusion and hemodynamic simulation has been neglected.Therefore,this study aims to explore the application value of DSA in these two aspects by using the DSA image data from patients with carotid artery stenosis.Firstly,in the evaluation of cerebral blood flow perfusion,DSA image data of thirty patients with a mild to severe stenosis on one side,and a mild stenosis on the other side of the internal carotid artery were collected.The time density curve(TDC)and the relevant DSA perfusion parameters of different brain tissue were extracted by using the DSA parametric imaging method.Then cerebral perfusion in patients with carotid stenosis were evaluated by comparing the differences in perfusion parameters of the frontal lobe,parietal lobe,temporal lobe and occipital lobe.The results show that it is feasible to extract TDC and calculate multiple perfusion characteristic parameters based on DSA images.When one side of the internal carotid artery was severely stenotic,bilateral asymmetrical changes occur in bilateral cerebral perfusion,especially in the frontal and parietal lobes.Some DSA perfusion parameters including MTT(mean transit time),TU(time of contrast uptake),1/2TMAX(time taken to half maximum value)and AUC(area under the curve),are good indicators to detect cerebral perfusion insufficiency.Secondly,in hemodynamic simulation,we collected the DSA image data of 30 patients with carotid artery stenosis,and the patients were divided into three groups: mild,moderate and severe stenosis,with 10 patients in each group.Then the carotid bifurcation models of these patients were constructed based on their DSA images.The method of calculating thecarotid artery flow ratio from DSA image was firstly proposed in order to obtain the actual carotid artery' outlet boundary conditions of the patients.The flow ratio was then used as the outflow boundary condition for the hemodynamic simulation.Furthermore,the simulation results were compared with those of hemodynamic simulation under the zero pressure outlet boundary condition to analyze the hemodynamic differences between different outlet boundary conditions.Compared with the DSA flow ratio condition,the simulation results of patients with severe carotid artery stenosis under the condition of zero pressure show a significantly smaller range of high TAWSS(time-averaged wall shear stress)and high TAWSSG values at the stenosis site,and the deviation rates of TAWSS,OSI(oscillating shear index)and TAWSSG(time-averaged wall shear stress gradient)also increase significantly.Therefore,in the case of severe carotid artery stenosis,the hemodynamic results calculated by using zero pressure boundary may have a large error,while the using of the outlet boundary condition based on patient image analysis can improve the accuracy of the numerical calculation results.Through the two aspect's study,we have demonstrated the feasibility of extracting the characteristics of cerebral blood flow perfusion parameters and the carotid outlet boundary condition based on the DSA images.It can provide reference value for the quantitative evaluation of cerebral blood perfusion and improving the accuracy of hemodynamic simulation results,which is helpful for clinicians to evaluate and treat carotid artery stenosis diseases.