Hemodynamic Studies Of The Influences Of Diverticulum Morphology On Sigmoid Sinus

Tinnitus is the abnormal auditory perception of sound by the human body without external stimuli,the incidence of tinnitus in the population is approximately 10%–15%,persistent pulsatile tinnitus（PT）severely affects a patient’s mental health,often leading to insomnia,irritability,depression,and even suicide.Pulsatile tinnitus（PT）originates from the noise produced by abnormal blood flow of blood vessels in the temporal bone area.Sigmoid sinus diverticulum is a kind of abnormal vascular and is the most frequent but treatable cause.The diverticulum has different morphology,and the influence of the diverticulum morphology on the hemodynamics of the sigmoid sinus is still unclear.The purpose of this study is to clarify the influence of diverticulum morphology on the hemodynamics of the sigmoid sinus and provide theoretical guidance for the treatment of pulsatile tinnitus.Therefore,we conducted a numerical simulation,4DFlow experiment and PIV experiment on the influence of the diverticulum depth,angle,position and entrance diameter that mainly characterize the morphology of the diverticulum on the hemodynamics of the sigmoid sinus.To clarify the influence of the morphology of the diverticulum on the hemodynamic environment of the sigmoid sinus,this study performed five aspects of research.1.Firstly,the CT image data of 26 patients with PT were obtained,secondly,the models（including the transverse sinus,sigmoid sinus,and jugular vein）were reconstructed,finally,performing statistical analysis on the diverticulum morphology among these models to clarify the range of the parameters that mainly characterize the morphology of the diverticulum:depth,angle,position and the entrance diameter,which lay a theoretical foundation for the follow-up research to establish ideal models of different morphology of diverticulum.2.CFD,PIV experiment and 4Dflow experiment were used to clarify the effect of the depth of diverticulum on the hemodynamics of sigmoid sinus.Based on the first study,firstly,four models of diverticulum depth of 9 mm,6 mm,3 mm and 0 mm were constructed for simulation calculation,and hemodynamic indicators such as vessel wall pressure,average wall pressure(P_avg),wall shear stress（WSS）,average WSS(WSS_avg),average vorticity(V_avg)and sigmoid sinus blood flow velocity were used for analysis qualitatively and quantitatively.Secondly,eight models were printed in UV Cureable Resin material,and the velocity field of the models were obtained by PIV experiment and the 4Dflow experiment,and compared with the results of the simulation calculation.3.CFD and 4Dflow experiment were used to clarify the effect of the angle of diverticulum on the hemodynamics of sigmoid sinus.Based on the first study,firstly,three models of diverticulum angle of 60°,90°and 120°were constructed for simulation calculation research,and hemodynamic indicators were obtained for comparative analysis qualitatively and quantitatively;secondly,three models were printed in UV Cureable Resin material,and the velocity field of the models were obtained by 4Dflow experiment,and compared with the results of the simulation calculation.4.CFD and PIV experiment were used to clarify the effect of the position of diverticulum on the hemodynamics of sigmoid sinus.Based on the first study,firstly,four models of diverticulum on the upper,lower,lateral and medial sides of the sigmoid sinus were constructed for simulation calculation,and hemodynamic indicators were obtained for comparative analysis qualitatively and quantitatively;secondly,one model was printed in UV Cureable Resin material,and the velocity field of the model was obtained by PIV experiment,and compared with the results of the simulation calculation.5.CFD and PIV experiment were used to clarify the effect of the entrance diameter of diverticulum on the hemodynamics of sigmoid sinus.Based on the first study,firstly,seven models of diverticulum entrance diameters of 16 mm,14 mm,12 mm,10 mm,8mm,6 mm and 4 mm were constructed for simulation calculations,and hemodynamic indicators were obtained for comparative analysis qualitatively and quantitatively;secondly,two model were printed in UV Cureable Resin material,and the velocity field of the model were obtained by PIV experiment,and compared with the results of the simulation calculation.Five results and conclusions were obtained:1.Four main parameters characterizing the morphology of the diverticulum were defined,including depth,angle,position and entrance diameter of the diverticulum,and statistical analysis showed that the depth ranges from 1.28 mm to 9.25 mm,the angle range ranges from 38.42°to135.98°,and the entrance diameter range ranges from 2.96mm to 17.38 mm,and the correlation between them is low,which lays the theoretical foundation for the subsequent construction of ideal diverticulum models with different shapes for single factor research.2.As the depth of the diverticulum decreased,the pressure on the wall of the diverticulum and the turbulence of blood flow in the sigmoid sinus showed a downward trend,and the WSS of the diverticulum did not change significantly.When the depth of the diverticulum decreased from 9 mm to 6 mm,the pressure of the diverticulum and the blood flow disorder of the sigmoid sinus remained almost unchanged.When the depth of the diverticulum decreased from 6 mm to 3 mm,the pressure of the diverticulum wall and the blood flow disorder of the sigmoid sinus significantly decreased,P_avg（case1,126.274 Pa vs.case2,106.897 Pa）,V_avg(case1,172.946 s^-1 vs.case2,142.963 s^-1).When the depth of the diverticulum decreases from 3mm to 0mm,the pressure of the diverticulum decreased significantly,and the blood flow disorder of the sigmoid sinus decreased less.Therefore,when the depth of the diverticulum is reduced to 3mm,the hemodynamics of the sigmoid sinus will be significantly improved,which may have a good effect on improving pulsatile tinnitus.3.With the change of the angle of the diverticulum,the wall pressure of the diverticulum,the vorticity of blood flow of sigmoid sinus,and the WSS did not change significantly.P_avg（case1,118.756 Pa vs.case2,118.003 Pa vs.case3,121.178 Pa）,V_avg(case1,160.64 s^-1 vs.case2,155.577 s^-1 vs.case3,150.059 s^-1),WSS_avg（case1,1.77682 Pa vs.case2,1.85834 Pa vs.case3,1.71738 Pa）.Therefore,the change of the angle of the diverticulum has no significant effect on the hemodynamics of the sigmoid sinus,and may have no effect on pulsatile tinnitus.4.With the change of the position of diverticulum,the hemodynamics of the SSD showed greater differences.In the lateral diverticulum model,the wall pressure of the diverticulum and the vorticity of blood flow in the sigmoid sinus are relatively the largest(case3,P_avg,145.48 Pa,V_avg,264.628 s^-1).The lateral diverticulum has a greater impact on the hemodynamics of the sigmoid sinus,so this type of diverticulum may have a greater impact on pulsatile tinnitus.5.With the decrease of the entrance diameter of the diverticulum,the wall pressure and blood flow turbulence of the SS showed a trend of increasing first and then decreasing.When the entrance diameter of the diverticulum was 10 mm,the pressure and vorticity of the diverticulum were significantly higher(case4,P_avg,140.814 Pa,V_avg,212.193 s^-1).Therefore,if the entrance diameter of the diverticulum is not reduced enough,the hemodynamic effects of the sigmoid sinus may be aggravated,and the pulsatile tinnitus may be more serious.Therefore,the SSD should be minimized to disappear.In summary,this article clarifies the influence of diverticulum morphology on the hemodynamics of the sigmoid sinus qualitatively and quantitatively,provides a theoretical basis for the study of PT,and has potential application value for the treatment of patients with PT.The results of 4DFlow experiment and PIV experiment were consistent with the results of numerical simulation,further verified the feasibility of numerical simulation for PT research.