OBJECTIVE:To investigate the effect of different types of transverse sinus stenosis on blood flow patterns in the ipsilateral superior curve of the sigmoid sinus.METHODS:According to the morphology of transverse and sigmoid sinus sections in pulsatile tinnitus patients, ten idealized models with different degrees and positions of transverse sinus stenosis were constructed. Computational fluid dynamics simulations were performed to compare the hemodynamic characteristics among these models. Follow-up images of previous cases were included, which preliminarily confirmed the hypothesis that bone plate erosion of the sigmoid sinus sulcus is related to blood flow impingement.RESULTS:Blood flow impingement on the superior curve of the sigmoid sinus wall intensified with increasing degree of stenosis and decreased with increasing distance between the stenosis and the sigmoid sinus. The impact zone was generally confined to the anterior and lateral walls of the superior curve of the sigmoid sinus. When the stenosis was located far from the middle of the transverse sinus, the blood flow impingement on the sigmoid sinus wall was very weak.CONCLUSIONS:When stenosis is located far from the sigmoid sinus, the causes of tinnitus should be comprehensively considered instead of assuming that stenosis is the main cause. Bone plate erosion of the sigmoid sinus sulcus was promoted by blood flow impingement.KEY POINTS:• Ten idealized models with different degrees and positions of stenosis were constructed. • The causes of pulsatile tinnitus should be comprehensively considered. • Sigmoid sinus plate dehiscence was promoted by blood flow impingement.

Objective: To calculate fractional flow reserve (FFR) based on computed tomography angiography (i.e., FFRCT) by considering the branch flow distribution in the coronary arteries. Background: FFR is the gold standard to diagnose myocardial ischemia caused by coronary stenosis. An accurate and noninvasive method for obtaining total coronary blood flow is needed for the calculation of FFRCT. Methods: A mathematical model for estimating the coronary blood flow rate and two approaches for setting the patient-specific flow boundary condition were proposed. Coronary branch flow distribution methods based on a volume-flow approach and a diameter-flow approach were employed for the numerical simulation of FFRCT. The values of simulated FFRCT for 16 patients were compared with their clinically measured FFR. Results: The ratio of total coronary blood flow to cardiac output and the myocardial blood flow under the condition of hyperemia were 16.97% and 4.07 mL/min/g, respectively. The errors of FFRCT compared with clinical data under the volume-flow approach and diameter-flow approach were 10.47% and 11.76%, respectively, the diagnostic accuracies of FFRCT were 65% and 85%, and the consistencies were 95% and 90%. Conclusions: The mathematical model for estimating the coronary blood flow rate and the coronary branch flow distribution method can be applied to calculate the value of clinical noninvasive FFRCT.

OBJECTIVE: To investigate the relationships between upstream venous sinus stenosis and pulsatile tinnitus (PT), and to assess the correlation with diverticulum growth and the effectiveness of stent implantation. METHODS: Patient-specific geometric models were constructed using computed tomography venography images from a patient with PT, with sigmoid sinus diverticulum, and with upstream transverse sinus stenosis, in whom stenting of the upstream sinus stenosis alone achieved complete remission of PT. Computational fluid dynamics simulation based on this patient-specific geometry was performed using commercially available finite element software (ANSYS-14) to qualitatively and quantitatively compare the flow velocity, flow rate, velocity vector, pressure, vorticity, and wall shear stress on the affected side transverse and sigmoid sinuses, before and after stent implantation. RESULTS: Stenting improved the flow direction and magnitude. After stenting, the flow pattern became smoother and more regular. High-speed blood flow at the level of the diverticulum neck was confined to a smaller area, and its direction changed from approximately perpendicular to the diverticular dome to the distal side of the diverticular neck. The diverticulum showed obvious flow reduction, with decreases of 80.7%, 68.7%, 96.1%, and 91.3% in peak velocity, inflow rate, pressure gradient, and peak vorticity, respectively. The abnormally low wall shear stress at the dome of diverticulum was eliminated. CONCLUSIONS: Our findings strongly support a major role of diverticulum stenosis before in PT development and suggest that such stenosis is a causative factor of diverticulum growth. They also confirm the effectiveness of stent implantation for the treatment of PT.