The Establishment Of The Hemodynamic Physical Models Of The Superficial Cerebrovenous System And Its Implication

Objectives To establish the hemodynamic physical models of the superficial cerebro- venous system with the methods of compute fluid dynamics (CFD), and to provide morphologic basis for the genesis of cerebral venous thrombosis (CVT) and their early diagnosis.Methods Based on the result of cadavers and neuroimaging and the CFD software pack– FLUENT and GAMBIT, the hemodynamic physical models were established. The haemodynamic parameters such as turbulence, wall shear stress (WSS) and velocity were carefully studied and compared between different models.Results 1. Five groups and eighty-eight models were established, including the physical models of superficial cerebral veins (SVs) with various angles drain into the dural sinus, the models of SVs with various diameters drain into the dural sinus, the models of SVs drain into the dural sinus via meningeal veins, the models of SVs drain into the dural sinus via outflow cuff, and the models of SVs with different boundary conditions. 2. The physical models of SVs with various angles drain into the dural sinus①The graphs between various angles and WSS were obtained. According to the graphs, the models were divided into three groups with the different angles: [10°, 60°] groups, (60°, 100°) groups and [100, 170] groups.②I n the [10°, 60°] groups, the turbulence was found in the dural sinus within 3.9±1.1 mm away from dural entrance and the SVs within 4.3±4.2 mm away from dural entrance. The WSS in the downstream wall of dural sinus (DSD) and the upstream wall of superficial cerebral veins (SVU) besides the turbulence decreased and was below the reference value (0.040 Pa). The minimum WSS in DSD and BVU was 0.022±0.001 Pa and 0.010±0.010 Pa. The later was lower than former. The distance from minimum WSS in DSD and BVU to dural entrance was 5.1±1.0 mm and 3.2±4.1 mm. The former was farther than later. The velocity of the inlet of dural sinus and SV and the outlet of dural sinus was 0.0979±0.0002 m/s, 0.0699±0.0022 m/s and 0.1480±0.0002 m/s.③In the (60, 100) groups, the turbulence was found in the dural sinus within1.5±0.7 mm away from dural entrance. The WSS in the DSD besides the turbulence decreased and was below the reference value. The minimum WSS in DSD was 0.022±0.001 Pa. The distance from minimum WSS in DSD to dural entrance was 2.5±0.7 mm. The extent of the turbulence and the decrease of WSS was less than the (60, 100) groups. The velocity of the inlet of dural sinus and SV, the outlet of dural sinus was 0.0979±0.0002 m/s, 0.0717±0.0003 m/s and 0.1480±0.0003 m/s.④In the [100, 170] groups, no turbulence was found in the lumens, and no WSS decreased in the vessel wall. The velocity of the inlet of dural sinus and SV, the outlet of dural sinus was 0.0998±0.0008 m/s, 0.0713±0.0008 m/s and 0.1504±0.0013 m/s. The velocity in the inlet and outlet of the dural sinus was higher than other groups. 3. The physical models of SVs with various diameters drain into the dural sinus①When the diameters of the SVs were less than 2.0 mm, the WSS in the vessel wall was keep normal. When the diameters of the SVs were more than 2.0 mm, the WSS decreased notablely in the DSD or SVU in the models of SVs with angles 45 or 90 degrees.②In the models of SVs with angles 90 degrees, with the rise of the diameter of the SVs, the distance from the minimum WSS to dural entrance decreased gradually, and the difference between the WSS in SVU and DSD was more serious.③When the diameters of the SVs were more than 4.5 mm, the velocity in the outlet of the dural sinus in the models of SVs with angle 90 degrees was less than the velocity in the models of SVs with angle 45 or 135 degrees. With the rise of the diameter of the SVs, the difference between them was more serious. 4. The physical models of SVs drain into the dural sinus via meningeal veins①In the models of SVs with the angles 45 degrees, the minimum WSS in the SVU was increased to normal after the minor menigeal veins changing the directon of the blood flow in SVs. The minimum WSS in the DSD was not changed notablely, but the distance from the minimum WSS to dural entrance decreased notablely.②In the models of SVs with the angles 90 degrees, the minimum WSS was under the reference value with SVs drain into dural sinus via menigeal veins.③I n the model of SVs with the angles 135 degrees, the minimum WSS was decreased to the value under reference with SVs drain into dural sinus via menigeal veins.④With the rise of diameter of the menigeal veins, the velocity in the inlet of SVs increased and the velocity in the inlet of dural sinus decreased. 5. The physical models of SVs drain into the dural sinus via outflow cuff①The WSS in the DSD was not changed notablely.②In the models of SVs with the angles 45 degrees, the WSS was increased to reference value.③With the decrease of the diameter of the outflow cuff, the velocity in the inlet of SV and the outlet of dural sinus decreased. 6. The physical models of SVs with different boundary conditions①When the pressure in the inlet of dural sinus and SVs changed simultaneously from 26.7 Pa to 60.0 Pa, there were no visible chang of the WSS. The radio between the pressure in the inlet of dural sinus and SVs was 1.0.②When the pressure in the inlet of dural sinus changed separatedly, the WSS increased to nomarl with the pressure 60.0 Pa. The radio between the pressure in the inlet of dural sinus and SVs was 1.5.③When the preesure in the inlet of SVs changed separatedly, the WSS increased to nomarl with the pressure 26.7 Pa. The radio between the pressure in the inlet of dural sinus and SVs was 1.5.Conclusion①The hemodynamic physical models of superficial cerebrovenous system are established successfuly.②There are two harmful morphologic characteristics of SVs. One is the SVs draining into dural sinus with the angles no more than 60 degrees, the diameters are no less than 2.0 mm, and draining into dural sinus not via meangeal veins or the outflow cuff. The other is the SVs draining into dural sinus with the angles more than 60 degrees, the diameters are no less than 2.0 mm, and draining into dural sinus via meangeal veins. The local WSS changs rapidly, and CVT occurs easily.③The predilection site of thrombosis is in the SVU and DSD within 10.0 mm away from the dural entrance.The thrombus are most likely occurring in the SVU, and are less likely occurring in the DSD.④With the increment of the diameter of SVs, the oppitunity of the CVT occurs is increased and the thrombus is occurred in the SVU more easily.⑤After the radio between the preesure in the inlet of dural sinus and in the inlet of SVs is increased, the oppitunity of CVT occurs decreased.