Hemodynamic Study Of Coil Embolization In The Treatment Of Pulsatile Tinnitus

Pulsatile tinnitus（PT）is the abnormal perception of sound by human ears without external stimulation.Its frequency is synchronized with the heart.Continuous tinnitus seriously affects the quality of life of patients,causing insomnia,irritability,depression and even suicide.Sigmoid sinus diverticulum（SSD）is a vascular anomaly in the transverse sigmoid sinus,which is a common cause of PT.Clinically,coil embolization is a new surgical method for the treatment of SSD PT.At present,the selection of coil embolization parameters mainly depends on the experience of clinicians or intracranial aneurysm embolization experience.The influence law of coil type,filling density and basket diameter on the hemodynamic environment in SSD is not clear.The purpose of this paper is to clarify the influence law of coil parameters on SSD hemodynamics,The main research contents are as follows:（1）The influence of coil type on the hemodynamic environment in SSD was studied by the combination of finite element method and computational fluid dynamics（CFD）.Firstly,the SSD model of three PT patients was reconstructed;Then,two types of coils,basketball coil and packing coil,were constructed by finite element method to simulate the release of coils in the SSD.CFD simulation was carried out based on the patient1-3 SSD model after the release of coil and set the control group（no coil）.The differences of hemodynamic changes in SSD after coiling of different types of coils were analyzed;Finally,the blood flow in the SSD is studied by particle image velocimetry（PIV）.The blood flow field obtained is in good agreement with the CFD simulation results.（2）The influence of coil packing density on the hemodynamic environment in SSD was studied by the combination of finite element method CFD.Based on the SSD model of three PT patients,the coil with filling density of 6%,12%,18%,24%was constructed by finite element method simulate the release of the coil in the SSD and set the control group（no coil）.The CFD simulation calculation was carried out on the patient1-3 SSD model after the release of the coil,and the difference of hemodynamic changes of SSD after embolization with coil with different filling density was analyzed.（3）The influence of coil basket diameter on the hemodynamic environment in the SSD was studied by the combination of finite element method and CFD.Based on the SSD model patient1-3 of three PT patients reconstructed in Study 1,the basket with a diameter of 0.6 was constructed by finite element method 0.6α,0.8α,α,1.2α,1.4αand simulate its release,whereαfor the width of SSD neck,CFD simulation was carried out on the patient1-3 vascular models after coiling,and the differences of hemodynamic changes of SSD after coil embolization with different basket diameters were analyzed.According to the above research contents,the following conclusions are obtained:（1）Coil type had an impact on the treatment effect of PT,and the complex coil effect was better.After complex coil embolization,the decrease of_（62）was higher than that of helical coil and the sigmoid sinus cortical plate dehiscence（SSCPD）area of patient1-3 control group_（62）（control group:180.2±16.1 Pa（mean±SD）;after the helical coil:173.9±16.7 Pa;after complex coil:166.6±18.1 Pa）.After coil embolization,the low velocity（<5mm/s）volume proportion of SSD area increased significantly.It was higher after complex coil embolization than that of the helical coil.The proportion of low velocity in SSD（control group:0.3±0.09%（mean±standard deviation）;after the helical coil:24.6±5.5%;after complex coil:32.4±10%）.（2）The relationship between the hemodynamics of SSD and filling density is not linear.When the local filling density of SSCPD area increases inconspicuously,_（62）and(2_（62）did not change significantly.The SSCPD area_（62）（filling density 0%:180.2±16.1 Pa（mean±SD）;filling density 6%:176.8±16.1 Pa;filling density 12%:173.6±15.5 Pa;filling density 18%:169.4±15.2 Pa;filling density 24%:169.3±14.5Pa）.The reduction of wall pressure and wall shear stress is the short-term hemodynamic mechanism of coil therapy for PT.The proportion of the low-velocity area in the SSD increased with the increase of packing density,and the proportion of the low-velocity（packing density 0%:0.3±0.09%vs.packing density 6%:5.1±2%vs.packing density12%:19.5±2%vs.packing density 18%:22.8%±3.5%vs.packing density 24%:28.1±3.9%）.The increased volume of the low-velocity region is beneficial to the thrombosis in the SSD,which is the long-term hemodynamic mechanism of coil therapy for PT.（3）When the diameter of the coil basket was equal to the width of the neck of the SSD,the_（62）、(2_（62）and the average vorticity value of in the area of SSCPD decreased most obviously,and the volume ratio of the low velocity area in the SSD was the highest.The_（62）of SSCPD area（basket diameter of is 0.6α:171.1±14.4 Pa（mean±SD）;basket diameter is 0.8α:167.8±17.5 Pa;basket diameter isα:168.1±22 Pa;basket diameter is 1.2α:175.9±19.8;basket diameter is 1.4α:171.3±15.7 Pa）.The proportion of the low-velocity area in the SSD of Patients1-3（basket diameter of is0.6α:27.5±6.8%（mean±SD）;basket diameter is 0.8α:31.9±1.76%;basket diameter isα:31.7±9.8%;basket diameter is 1.2α:27±0.14%;basket diameter is 1.4α:26.7±5.4%）.When the diameter of the basket is equal to the width of the SSD neck,the improvement of hemodynamics in the SSD after coil embolization is the best.