Aike Qiao

Computational Study of Stented Aortic Arch Aneurysms

This computational study is motivated by the fact that there is still incomplete knowledge to date about hemodynamics of stented aortic arch aneurysms harboring a bleb. The hemodynamics in the stented and nonstented models of aortic aneurysms were analyzed and compared using the method of computational fluid dynamics. Flow activities inside the stented aneurysm model were significantly diminished, specifically the pressure and wall shear stress in the bleb were decreased, thus promoting intra-aneurysmal thrombus development and attenuating aneurysm rupture risk. The present study indicated that it is effective to treat aortic arch aneurysms with endovascular stents

Numerical Simulation in Aortic Arch Aneurysm

The aorta, acting as the main conduit through which cardiac output is delivered to the systemic arterial bed, is continuously exposed to high pulsatile pressure and shear stress, making it prone to mechanical injury. It is also more prone to rupture than other vessels, particularly with the development of aneurysmal dilation. Fifty percent of patients who experience a rupture of a aortic aneurysm die before reaching the hospital (Bengtsson & Bergqvist, 1993). The incidence increases with age and has been reported as 6 per 100,000 person-years (Knowles & Kneeshaw, 2004). Aneurysmal degeneration that occurs in the aortic arch is termed a aortic arch aneurysm. Patients who have aortic arch aneurysm have multiple aortic lesions or aneurysmal disease which involves segment of aorta (Crawford et al., 1984). Aortic arch aneurysms represent only 10% of aneurysms of the thoracic aorta and it has higher risk of rupture than other aneurysm (Knowles & Kneeshaw, 2004). Blood flow through the aorta is one of the most complex flow situations found in the cardiovascular system. Blood flow is pulsatile and pressure inside aortic aneurysm is nonuniform. The dynamics interaction between blood flow and wall may influence the wall stress. Computer modeling has made impressive progress in scientific, engineering, biological and medical applications in recent years and it offers the prospect of providing both a better insight into a range of biomechanical problems and improved tools for the design of medical devices and the diagnosis of pathologies. Computational methods such as mathematical modeling methods (Rideout, 1991; Rupnic & Runvovc, 2002; Abdolrazaghi et al., 2008), computational fluid dynamics methods, (Botnar et al., 2000; Shahcheraghi et al., 2002; Morris et al., 2005; Tokuda et al. 2008) loosely coupled methods (Di Mrrtino et al., 2001; Gao et al., 2006abc) have been used to simulate the biomechanical problems in arotic arch and aortic arch aneurysm. The aim of this chapter is to describe the numerical simulation and computer modeling work in aortic arch aneurysm.

A Study on a LVAD of a Wear-free Heart Pump

This paper deals with hydrodynamic elements in a left ventricular assist device (LVAD) of a wear-free heart pump, a rigid rotor with translational and slop motion suspended in an active magnetic bearing (AMB) system. First, the modeling of the dynamic behaviour of the rotor is pointed out. Then, the control strategy is developed. It is based on a suggested control method considering with the coupling effect from both ends of the rotor. The controller is executed on a DSP board. Simulation results and experiment results show the efficiency of the control strategy and validates the method applied to the pump

Can interventional ablation be applied to the treatment of arterial aneurysm

Interventional therapy is commonly applied to the treatment of arterial aneurysm. Thermal ablation features rapid and minimal invasive treatment. A hypothesis of combining these two techniques was proposed to treat arterial aneurysm. An antenna is delivered with a catheter into the aneurysm sac and heated with microwave or RF, and hence induces instant coagulation and thrombosis of blood flow in the aneurysm sac so that the treatment motivation is achieved. The initiation of this hypothesis is to overcome the disadvantages of biological/mechanical mismatch between the interventional devices and the arteries in the interventional therapy, also utilize the advantages of rapid treatment and minimal invasion in the thermal ablation procedure.

Thermal field analysis in microwave ablation therapy for atrial fibrillation

The heart tissue is rich in blood, which flow is a thermal diffusion process; it can lead to lesion shape differences. The temperature distribution is very hard to obtain through the antenna specific absorption rate, thus affect curative effect. Based on the Pennes bioheat transfer equation, high flow rate of blood effect on microwave ablation in atrial fibrillation was analyzed. Lesion depths and diameters were analyzed.

Numerical simulation of RF catheter ablation for the treatment of arterial aneurysm

Considering the blood coagulation induced by the heating of radio frequency ablation (RFA) and the mechanism of aneurysm embolization, we proposed that RFA may be used to treat arterial aneurysm. But the safety of this method should be investigated. A finite element method (FEM) was used to simulate temperature and pressure distribution in aneurysm with different electrode position, electric field intensity and ablation time. When the electrode is in the middle of the artery aneurysm sac, temperature rose clearly in half side of artery aneurysm, which is not suitable for RFA. Temperature rose in the whole aneurysm when the electrode is under the artery aneurysm orifice, which is suitable for the ablation therapy. And in this way, the highest temperature was 69.585°C when power was 5.0 V/mm with 60 s. It can promote the coagulation and thrombosis generation in the aneurysm sac while the outside tissue temperature rises a little. Meanwhile, the pressure (10 Pa) at the top of aneurysm sac with electrode insertion is less than that (60 Pa) without electrode, so electrode implant may protect the aneurysm from rupture. The results can provide a theoretical basis for interventional treatment of aneurysm with RFA.