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1.
目的提出不同于传统支架的三角形网丝截面支架,并对其进行数值模拟,比较圆形、矩形、三角形截面支架在动脉瘤内的血流动力学效果。方法构建3个有支架植入的动脉瘤模型,分别为圆形(CM型)、矩形(RM型)和三角形(TM型)截面支架模型,并与1个无支架的动脉瘤模型(UM型)对照。在相同的边界条件下,利用有限单元法对4个模型进行流固耦合数值模拟。结果 RM型比TM型和CM型的速度更低、流阻更高、流转时间更长,所以矩形、三角形、圆形截面支架血液流动的影响效果依次降低。在削弱壁面切应力大小、降低壁面切应力波动性方面,RM型比TM型和CM型更加显著,但CM型和TM型的壁面升压低于RM型。壁面应力分布和变形结果表明动脉瘤沿远侧壁生长的可能性大于近侧壁,瘤顶破裂的风险最大。结论 3种截面支架展示了不同的血流动力学,这些结果为血管内支架的结构设计和优化提供了有意义的参考依据。  相似文献   

2.
血管支架作为治疗颅内动脉瘤的新方法被广泛运用到临床中,而且越来越普遍。但由于某些支架植入后不能满足力学要求或对瘤内血液动力学无明显影响,反而更易形成血栓,造成动脉瘤破裂。本研究首先通过结构静力学分析比较矩形截面网格状支架和网丝编织成的圆形截面螺旋形支架的弯曲变形能力及扭转变形能力;然后将网格支架植入实际脑动脉瘤模型,进行流-固耦合模拟仿真,分析血流速度、壁面压力及壁面剪切力变化。结果表明:两种支架能够在不损失径向支撑力的情况下,提供良好的轴向顺应性,且网格状支架的变形能力高于螺旋状支架;支架植入后血液动力学各项指标明显降低。血管支架对颅内动脉瘤血液动力学有很大影响,可为临床治疗动脉瘤提供理论依据。  相似文献   

3.
目的 构建蜿蜒型动脉瘤和弯曲支架三维有限元模型,研究支架植入动脉瘤后的血流动力学的变化。方法 通过CAD软件构建出几何实体模型,借助有限元软件利用计算流体力学方法,分别对无支架和有支架的蜿蜒型脑动脉瘤定常流动血流动力学进行数值模拟,分析在动脉瘤中植入内支架前后的瘤腔内流动情形、压力和壁面切应力分布的变化情况。结果 有支架动脉瘤模型上游瘤腔内的血流速度被大大削弱,圆顶突起处局部高压力明显减弱,在下游瘤腔沿壁面的压力也得到明显降低并且分布也均衡了很多,末端唇缘处局部高切应力消失了,出现的是较小且均衡的切应力。结论 有支架模型瘤腔内的流速明显减小,均衡的压力分布与瘤腔内减弱的流动速度是相互统一的,利于瘤腔内血栓的形成。  相似文献   

4.
半圆形截面支架介入串联囊状动脉瘤的血流动力学仿真   总被引:1,自引:0,他引:1  
为了研究半圆形截面支架对颅内串联囊状动脉瘤血流动力学的影响,针对同一动脉瘤结构,构建无支架和4种截面支架介入动脉瘤的有限元模型,分别命名无支架为U型、圆形截面为C型、半圆形截面圆面朝向瘤腔为ES型、圆面朝向血管轴向为IS型,然后对模型中的生理脉动流进行计算流体动力学仿真。数值模拟的结果显示:有支架模型的腔内流速被有效削弱,壁面附近的流速很低;血流对瘤腔的冲击减弱,壁面切应力的量值和波动性降低,分布均衡;腔内压力在支架介入后略有升高。对比分析两个瘤腔,流动情况和壁面切应力基本相同,下游瘤腔的压力低于上游瘤腔。IS型的仿真结果更好,这为支架的结构设计提供了一些理论指导。  相似文献   

5.
研究不同结构形状的血管支架用于治疗颅内动脉瘤后对血流动力学的影响。针对同一个体化颅内动脉瘤模型,设计了三种网丝截面相同、通透率近似相等、结构形状不同的支架。将这三种支架植入颅内动脉瘤模型,进行双向流固耦合数值模拟,分析血流速度、壁面切应力的变化情况。三种支架中,螺旋型支架对动脉瘤瘤腔内的血流旋涡改善效果最佳,对动脉瘤瘤颈和瘤顶部分较高的壁面切应力削弱也最明显;周期型支架的柔顺性优于其余两种类型的支架。螺旋型支架植入颅内动脉瘤的治疗效果最佳,但不适合几何形状复杂的血管,本研究也可为进一步优化支架结构提供依据。  相似文献   

6.
目的 利用数值模拟研究具有病人特异性的脑动脉瘤内的血液流动,为脑动脉瘤的破裂风险的评价和动脉瘤介入栓塞后复发风险的评价提供帮助。方法 从两例脑动脉瘤病人的3D-RA数据中重建动脉瘤几何模型,血液流变学模型选择假塑性非牛顿流体模型,利用商用CFD软件Fluent对两例动脉瘤内的血液流动进行数值模拟。结果 数值模拟给出了动脉瘤内的流线图、重要截面上的速度分布图、壁面上的切应力分布和压力分布图。并且绘制了在收缩期时刻动脉瘤颈部和瘤顶部各20个点上的壁面切应力和压力的变化情况。结论 血流动力学因素如流速、压力、壁面切应力、流动对壁面的冲击状况等因素与动脉瘤的生长和破裂密切相关,而由于脑动脉瘤形态各异、载瘤动脉与动脉瘤体的几何关系复杂,所以具有病人特异性的数值模拟对于研究动脉瘤破裂和复发风险具有重要价值。动脉瘤颈部的壁面切应力和壁面切应力的波动的变化规律并不相同,需要进一步研究壁面切应力的波动与脑动脉瘤生长与破裂之间的定量关系。  相似文献   

7.
目的 研究不同结构形状以及不同网丝截面的支架用于颈内动脉瘤治疗后对血液动力学及支架柔顺性的影响。方法 针对同一个体模型的颈内动脉瘤,构建5种不同支架介入治疗的模型。这些支架的支撑体网丝截面不同,但支架通透率近似相等。利用有限体积法进行数值仿真,获得其生物力学特性的定量信息。结果 5种模型中,矩形截面网格支架模型动脉瘤腔中平均流动速度的减小幅度最大;圆型截面支架和矩形截面螺旋支架模型中瘤面和瘤颈部分的壁面切应力减小面积较大;网格支架的柔顺性要远好于螺旋支架。结论 矩形截面网格支架对治疗颈内动脉瘤有较好的生物力学影响,这些发现可帮助临床医生在治疗脑动脉瘤时选择合适的支架。  相似文献   

8.
目的探讨瘤用支架血流动力学流固耦合数值模拟过程中不同计算周期的相对误差大小,以给出获得收敛结果的最小周期推荐值.方法利用有限元分析软件 ANSYS对植入不同截面形状支架治疗梭形动脉瘤模型进行流固耦合数值模拟.每个模型进行3个周期的迭代计算,计算出各模型的动脉瘤腔内血液流速、压力、壁面切应力等血流动力学参数.最后比较相邻周期的相对误差绝对值,根据数据后处理结果得到计算的最佳周期数.结果各模型的动脉瘤腔内血流动力学参数计算1周期与计算2周期的相对误差绝对值远高于5%,重复计算3个周期与计算2个周期的相对误差绝对值均小于5%.结论有限元分析软件 ANSYS进行支架非定常血流动力学流固耦合数值模拟计算时,计算2个周期可达一定精确度,避免不必要的时间消耗,为支架治疗梭形动脉瘤的流固耦合数值模拟研究提供参考依据.  相似文献   

9.
目的研究截面为不同旋转角度的三角形支架对颅内动脉瘤血流动力学的影响。方法采用非均匀格子Boltzmann方法对支架区域进行局部加细,并结合曲边界处理格式对置入支架的颅内动脉瘤进行数值模拟。通过对动脉瘤内流动形态、瘤口速度、瘤内速度减小量等动力学参量的分析,探讨不同旋转角度支架用于治疗颅内动脉瘤的效果。结果在减小瘤内血流速度方面,旋转角为180°的三角形截面支架效果最好,无旋转的三角形截面支架引起的速度减少量最小。在孔隙率较低情况下,截面为不同旋转角度的三角形支架起到效果差异较小。结论非均匀格子Boltzmann方法结合曲边界处理格式可以较准确地研究动脉瘤血流动力学特性,为支架的设计提供参考依据,并为临床介入治疗法提供一定的指导。  相似文献   

10.
目的研究截面为不同旋转角度的三角形支架对颅内动脉瘤血流动力学的影响。方法采用非均匀格子Boltzmann方法对支架区域进行局部加细,并结合曲边界处理格式对置入支架的颅内动脉瘤进行数值模拟。通过对动脉瘤内流动形态、瘤口速度、瘤内速度减小量等动力学参量的分析,探讨不同旋转角度支架用于治疗颅内动脉瘤的效果。结果在减小瘤内血流速度方面,旋转角为180°的三角形截面支架效果最好,无旋转的三角形截面支架引起的速度减少量最小。在孔隙率较低情况下,截面为不同旋转角度的三角形支架起到效果差异较小。结论非均匀格子Boltzmann方法结合曲边界处理格式可以较准确地研究动脉瘤血流动力学特性,为支架的设计提供参考依据,并为临床介入治疗法提供一定的指导。  相似文献   

11.
Background: Racemic albuterol is an equal mixture of (R)-albuterol (levalbuterol), which is responsible for the bronchodilator effect, and (S)-albuterol, which provides no benefit and may be detrimental. Objective: We sought to compare 2 doses of a single enantiomer, levalbuterol (0.63 mg and 1.25 mg), and equivalent amounts of levalbuterol administered as racemic albuterol with placebo in patients with moderate-to-severe asthma. Methods: This was a randomized, double-blind, parallel-group trial. Three hundred sixty-two patients 12 years of age or older were treated with study drug administered by means of nebulization 3 times daily for 28 days. The primary endpoint was peak change in FEV1 after 4 weeks. Results: The change in peak FEV1 response to the first dose in the combined levalbuterol group was significantly greater compared with the combined racemic albuterol group (0.92 and 0.82 L, respectively; P = .03), with similar but nonsignificant results after 4 weeks (0.84 and 0.74 L, respectively). Improvement in FEV1 was similar for levalbuterol 0.63 mg and racemic albuterol 2.5 mg and greatest for levalbuterol 1.25 mg. Racemic albuterol 1.25 mg demonstrated the weakest bronchodilator effect, particularly after chronic dosing. The greatest increase in FEV1 was seen after levalbuterol 1.25 mg, especially in subjects with severe asthma. All active treatments were well tolerated, and β-adrenergic side effects after administration of levalbuterol 0.63 mg were reduced relative to levalbuterol 1.25 mg or racemic albuterol 2.5 mg. At week 4, the predose FEV1 value was greatest in patients who received levalbuterol or placebo when compared with those who received racemic albuterol. The difference was more evident and was statistically significant in patients who were not receiving inhaled corticosteroids. Conclusion: Levalbuterol appears to provide a better therapeutic index than the standard dose of racemic albuterol. These results support the concept that (S)-albuterol may have detrimental effects on pulmonary function. (J Allergy Clin Immunol 1998;102:943-52.)  相似文献   

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Background: The use of rituximab (RTX) is increasing, even in developing countries. It has become the first-line therapy or adjuvant to chemotherapy (CHOP; cyclophosphamide, hydroxydaunorubicin, oncovin and prednisone) for various diseases, including B cell lymphoma and autoimmune diseases.

Aim: We describe the infectious diseases and immunological markers associated with RTX treatment of patients with non-Hodgkin lymphoma (NHL).

Methods: Serum immunoglobulins were determined before and after intravenous immunoglobulin (IVIg) administration. Pneumo-23IgG-specific anti-pneumococcal antibodies were evaluated before and after vaccination. Immunophenotyping and lymphocyte proliferation were determined in the course of the treatment.

Results: Seven patients were followed and median age was 56.0?±?5.0?years (range, 41.9–71.6?years). At baseline, the mean level of IgG was 333.7?±?40.8?and IgM 40.9?±?11.3?mg/dL, respectively; immunoglobulin A and E (IgA and IgE) were under the limit of detection. Two patients had reduced or absent B cells and T cell subsets were at normal levels in five patients. All patients failed to mount an efficient post-vaccination immune response against hepatitis B virus, tetanus, diphtheria and against the 23-valent pneumococcal polysaccharide vaccine. During RTX/CHOP treatment, human-IgG-immunoglobulin (IVIg) therapy was introduced in six patients after recurrent infections, including community-acquired pneumonia (85.7%), chronic sinusitis (85.7%) and gastroenteritis (42.9%).

Conclusion: Poor response against pneumococcal vaccines increases the susceptibility of respiratory diseases in these patients. In patients with NHL treated with RTX, the benefits achieved with IVIg replacement for the control of recurrent infectious diseases is of paramount importance. Clinicians dealing with monoclonal antibodies against cancer therapy, especially RTX, should be aware of the increasing risks for symptomatic induced hypogammaglobulinemia and respiratory infections.  相似文献   

17.
Summary A putative nonstructural protein encoded by a satellite RNA associated with bamboo mosaic potexvirus shares 46% identity with the capsid protein of satellite virus of panicum mosaic sobemovirus. The sequence similarity among satellite plant viruses which have no apparent relationship implies a common origin.  相似文献   

18.
目的 观察拉米夫定与泛昔洛韦联合治疗乙型肝炎病毒(HBV)慢性感染的临床疗效。方法 慢性乙型肝炎患者90例。设联合治疗组28例,单用拉米夫定组30例,单用泛昔洛韦组32例。联合治疗组给予口服拉米夫定0.1g/d(PO),泛昔洛韦1.5g/d(PO),24周。拉米夫定、泛昔洛韦单用组剂量及疗程分别同联合治疗组。结果 3组均无明显副反应,丙氨酸转氨酶(ALT)复常率无差异。3组HBV DNA阴转率分别为89.3%、66.7%、40.6%,差异有显著性。乙型肝炎表面抗原(HBeAg)阴转率分别为28.6%、23.3%、21.9%,差异无显著性。结论 拉米夫定与泛昔洛韦联合用药安全、耐受性好,临床显示联合治疗对HBV DNA的抑制作用显著优于单用药。  相似文献   

19.
Abstract

The incidence of self-mutilation and suicidality among patients with dissociative disorders is quite high. It is necessary for clinicians working with this population to be adept at dealing with safety problems. This article presents a sequence of basic steps that can be used when helping dissociative patients establish safety, a discussion of the functions of self-destructiveness, and an overview of specific experiences and thinking patterns that contribute to self-destructiveness among dissociative patients.  相似文献   

20.
Intervention with epinephrine in hypotension associated with mastocytosis   总被引:1,自引:0,他引:1  
The occurrence of the episodes of vasodilatory hypotension can be a life-threatening manifestation of systemic mastocytosis. This article describes the reversal by epinephrine of episodes of severe hypotension in two hospitalized patients with mastocytosis. Recognition of the efficacy of epinephrine in hypotension associated with mastocytosis can be important when other methods fail to restore hemodynamic stability.  相似文献   

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