鼻腔结构的三维重建与气体流场数值模拟

根据某鼻腔疾病患者的CT图像，用表面重建的方法对该患者的鼻腔结构进行三维重建，根据统计得出的呼吸潮气量以及呼吸周期假设一个呼吸周期内的鼻腔中气流流速的变化。用有限元的方法对鼻腔域中的气体流动进行了数值模拟及分析，并把得到的结果与医学文献中记载的数据相比较，说明本文计算结果是可信的。从文中的数值结果可以定量得到人体呼吸过程中，气体流场在鼻腔中的分布。     

鼻腔气道结构对鼻腔加温加湿功能影响的数值模拟

目的研究鼻腔气道结构的变化对鼻腔加温加湿功能的影响。方法选取9例正常人和2例鼻中隔偏曲患者(术前术后)作为研究对象,建立鼻腔的三维有限元模型,数值模拟鼻腔气道中的气流分布、气流温度和湿度,并对比正常人与病患、术前与术后的数值模拟结果。结果鼻腔气道宽敞一侧气流体积流率相对较大,加温加湿效果差;狭窄一侧加温效果相对较好。对于正常人,鼻腔对吸入气流加温加湿的部位主要位于前端;对于病患,则要取决于鼻腔的气道结构。结论鼻腔气道结构影响鼻腔对吸入气流的加温加湿效果,鼻腔气道结构的几何参数如鼻腔气道壁面积、鼻腔体积可以用来衡量鼻腔对气流的加温加湿效果。     

鼻腔结构矫正手术对OSAHS患者上气道流场影响的数值分析

目的研究伴鼻腔结构异常的OSAHS患者经鼻腔结构矫正手术后,气道结构形态的改变对患者整个上气道流场分布以及软腭运动姿态的影响。方法基于患者手术前后CT影像学数据,建立上气道及软腭三维有限元模型,采用流固耦合的方法模拟手术前后上气道流场特性及软腭的运动情况。结果手术矫正了异常的鼻腔结构形态,鼻腔及整个上气道阻力明显下降。术后软腭的肥厚水肿明显缓解,其游离缘的运动幅度减小。软腭运动幅度随弹性模量的减小而增大。术后的模拟结果与文献报道的正常人实验与模拟结果接近。结论鼻腔结构矫正手术改变了上气道结构,影响了气流流场的分布和软腭的运动姿态;不同病理生理状态下,软腭弹性模量的变化对其运动姿态有影响。     

单侧下颌骨牵张成骨的数值模拟

目的针对颜面短小患者建立下颌骨及咀嚼肌模型,通过有限元方法研究牵张成骨过程中下颌骨的形变规律,并与患者实际手术效果进行对比,为类似病例的治疗过程提出改进意见。方法依据临床颜面短小患者原始数据,结合MIMICS医学影像控制系统软件,运用三维重建技术构造患者下颌骨及咀嚼肌的实体结构,最后导入ANSYS有限元软件完成单侧下颌骨延长的有限元模型,并模拟手术效果。结果所建立的术前术后有限元分析模型具有数字化、个性化特征。结论数值模拟结果与手术效果进行对比,重合度较好,可以为不同病情的病人术前提供个性化的手术指导。     

鼻腔内一氧化氮分布的实验及数值研究进展

一氧化氮(nitric oxide,NO)在鼻腔内参与抗菌、抗病毒、促进鼻黏膜纤毛摆动、调节鼻黏膜血管扩张等多种生理功能。 NO 浓度异常会导致多种鼻腔疾病的发生,已成为临床常规检测气道炎症的生物学指标。 随着医学与力学等领域的深入交叉,运用数值研究方法,与传统的实验方法相结合,对鼻腔内 NO 浓度分布进行分析,可量化鼻腔内各处 NO 浓度,获得鼻腔内 NO 的分布规律,辅助相关鼻腔疾病的临床诊疗,有助于推动精准医疗的发展。 本文对鼻腔内 NO 浓度分布实验研究及数值研究的进展进行综述,并对未来研究方向进行展望。     

不同力学激励对骨重建数值模拟的影响

目的研究采用应变能密度、等效应力、等效应变3种不同力学激励对骨重建数值模拟结果的影响。方法建立股骨近端的二维有限元模型,基于力学稳态理论的重建控制方程并结合有限元法,分别用3种不同力学激励模拟股骨近端的内部结构及密度分布,并与CT数据计算得到的骨密度值进行定量分析比较。结果 3种力学激励模拟得到的重建结果均能反映出股骨近端的主要特征结构,但采用等效应力作为激励时得到的股骨密度曲线图的趋势和数值都与CT图像数据更为一致。结论在骨重建力学调控机制中,应力可能起主导作用。准确预测和模拟骨重建过程将对矫形外科、骨伤治疗、人工假体的优化和个体化设计等临床实践提供理论依据。     

基于CT图像三维重建支气管内气体流动特性

目的探讨低温气体在肺支气管内部的传质机理,为制定低温通气冷却无心跳供体肺方案提供理论依据。方法基于人体肺部CT图像三维重建得到真实支气管模型,并采用计算流体动力学方法研究往复式通气过程中不同通气频率(0. 5、0. 25、0. 125 Hz)条件下支气管内不同区域的流动分布特点。结果往复式通气过程中真实支气管内流动呈现出复杂的三维流动特征,且吸气和呼气过程中支气管不同区域的流动结构各不相同;真实支气管不规则的几何结构会对其内部流动产生重要影响;通气频率从0. 5 Hz逐渐减小到0. 125 Hz过程中,支气管不同区域边界层厚度逐渐增大,同时高速主流也得到不同程度增强。结论相比理想圆管模型,基于CT三维重建得到的支气管模型能够更加准确反映支气管内部流动结构。研究结果对于无心跳供体肺低温通气冷却技术的优化具有重要指导意义。     

呼吸道内颗粒物沉积的数值模拟

目的通过数值模拟方法研究人呼吸过程中吸入的颗粒物在呼吸道内的沉积规律及其影响因素。方法建立正常人呼吸道三维数值模型,模拟吸气过程中气流在呼吸道内的分布规律。在鼻孔或口等气流入口处释放颗粒,模拟悬浮颗粒物随着吸入气流在呼吸道内的沉积过程。同时改变颗粒物直径、密度、呼吸气流速率等参数,通过对比分析,研究颗粒物在呼吸道内沉积的影响因素。结果颗粒物在呼吸道内主要沉积在鼻阈、固有鼻腔气道中部、鼻咽部以及支气管内壁,并且颗粒物的沉积率随着其直径、密度、呼吸气流速率的增大而增加,几个参数对沉积率的影响程度也不相同。结论颗粒物在呼吸道内主要沉积在气道几何形状复杂或者气道走向剧烈改变的位置,颗粒物的直径、密度、呼吸气流速率均会影响到其在呼吸道内的沉积率。研究结果可为空气污染引发呼吸道疾病风险的临床评估提供数值依据。     

血管狭窄下游流场边壁压力分布的模型实验和数值模拟

针对低切应力不能完全解释狭窄下游流场内病变和病变严重程度分布的规律，本研究在已经建立的狭窄体外流体力学特性实验研究模型上，对流体力学的另一重要因素——压力进行检测，结合数值模拟的方法对其分布及分布变化规律进行深入研究。结果显示：模型实验检测和数值模拟计算结果一致性良好；狭窄下游流场出现显著的压力下降。低压力的分布区域与心血管狭窄病变的分布区域及其严重程度之间有高度的相似。研究提示：数值模拟计算可应用于微观流场的流体力学特性研究；狭窄下游流场低压力的分布和变化可能是低切应力之外导致局部血管边壁损伤的又一重要流体力学因素。     

无心跳供体肺支气管内气体三维流动的数值模拟研究

无心跳供体肺（NHBD）有望解决临床供肺严重不足的问题,肺内低温通气被公认为是NHBD肺在体低温保护的有效方法之一,可提高供肺的利用率。通过建立三维非对称四级支气管模型,运用计算流体动力学(CFD)方法对支气管内的气流流动特性进行数值模拟,并通过试验对数值模拟的边界条件进行验证。研究结果表明：在被动呼吸的吸气和呼气时,支气管截面上的无量纲速度分布不同,左肺支气管和右肺支气管截面上的速度分布也存在较大差异,其中左肺下叶支气管内中心线上的无量纲速度峰值最大,达到1.7,而右肺上叶支气管内中心线上的无量纲速度峰值最小,仅为0.8;由于分叉角度和管径不同,导致吸气过程中流入左主支气管内和右主支气管内的流量分别占55%和45%,而左肺下叶支气管内的流量比率在各肺叶支气管内的流量比率最高,约为35%;通过分析支气管内的流动压力损失,得出支气管的平均压降系数与Re的关系为p∝Re^－0.6。可见,由于支气管的非对称结构以及分叉处空间旋转角度的存在,使得支气管内的气体流动结构比较复杂,这对于无心跳供体肺原位通低温保存的临床实验研究有一定的参考价值。     

In Vitro Experiments and Numerical Simulations of Airflow in Realistic Nasal Airway Geometry

Pressure–flow relationships measured in human plastinated specimen of both nasal cavities and maxillary sinuses were compared to those obtained by numerical airflow simulations in a numerical three-dimensional reconstruction issued from CT scans of the plastinated specimen. For experiments, flow rates up to 1500 ml/s were tested using three different gases: HeO₂, Air, and SF₆. Numerical inspiratory airflow simulations were performed for flow rates up to 353 ml/s in both the nostrils using a finite-volume-based method under steady-state conditions with CFD software using a laminar model. The good agreement between measured and numerically computed total pressure drops observed up to a flow rate of 250 ml/s is an important step to validate the ability of CFD software to describe flow in a physiologically realistic binasal model. The major total pressure drop was localized in the nasal valve region. Airflow was found to be predominant in the inferior median part of nasal cavities. Two main vortices were observed downstream from the nasal valve and toward the olfactory region. In the future, CFD software will be a useful tool for the clinician by providing a better understanding of the complexity of three-dimensional breathing flow in the nasal cavities allowing more appropriate management of the patient's symptoms.     

藻酸钙棉条在鼻腔手术中的应用

为了探讨藻酸钙棉条在鼻腔术后填塞的效果 ,随机分组采用藻酸钙棉条 (实验组 )和碘仿纱条 (对照组 )填塞术后鼻腔 ,观察记录病人头痛和术腔粘膜恢复情况。表明 :(1)实验组病人头痛及鼻腔胀痛发生率明显降低 ,与对照组差异显著 (p<0 .0 0 0 5 )。 (2 )实验组术腔粘膜恢复情况优于对照组 (p <0 .0 5 )。藻酸钙棉条填塞术后鼻腔 ,病人头痛少 ,创面恢复快。     

不同洞径Ⅰ类洞修复后牙体的应力分析

我们旨在研究不同洞径Ⅰ类洞复合树脂修复后牙体的应力分布情况。采用CT扫描获取健康成人上颌牙的二维图像，通过计算机重建技术建立三维立体图像，并获得其有限元数据模型，在相同垂直载荷下对5种不同洞径Ⅰ类洞修复前后的牙体应力状态进行数据分析。结果显示，在所设计的圆三角形Ⅰ类洞受到50N相同作用力后，洞底切面直径从3．3nm逐步长到3．7nm时，其应力峰值依次为14．873、16．682、17．589、17．307和17．912MPa，各值间无明显差异，但应力峰值为正常牙的3倍。提示后牙树脂充填时，Ⅰ类洞洞径的改变对牙体的应力峰值无显著影响，但牙体的承载能力较正常牙明显下降。     

Transport Phenomena in the Human Nasal Cavity: A Computational Model

Nasal inspiration is important for maintaining the internal milieu of the lung, since ambient air is conditioned to nearly alveolar conditions (body temperature and fully saturated with water vapor) on reaching the nasopharynx. We conducted a two-dimensional computational study of transport phenomena in model transverse cross sections of the nasal cavity of normal and diseased human noses for inspiration under various ambient conditions. The results suggest that during breathing via the normal human nose there is ample time for heat and water exchange to enable equilibration to near intraalveolar conditions. A normal nose can maintain this equilibrium under extreme environments (e.g., hot/humid, cold/dry, cold/humid). The turbinates increase the rate of local heat and moisture transport by narrowing the passageways for air and by induction of laminar swirls downstream of the turbinate wall. However, abnormal blood supply or mucous generation may reduce the rate of heat or moisture flux into the inspired air, and thereby affect the efficacy of the process. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 8710+e     

Effects of Differences in Nasal Anatomy on Airflow Distribution: A Comparison of Four Individuals at Rest

Differences in nasal anatomy among human subjects may cause significant differences in respiratory airflow patterns and subsequent dosimetry of inhaled gases and particles in the respiratory tract. This study used computational fluid dynamics (CFD) to study inter-individual differences in nasal airflow among four healthy individuals. Magnetic resonance imaging (MRI) scans were digitized and nasal-surface-area-to-volume ratios (SAVR) were calculated for 15 adults. Two males and two females, representative of the range of SAVR values, were selected for flow analysis. Nasal CFD models were constructed for each subject by a semi-automated process that provided input to a commercial mesh generator to generate structured hexahedral meshes (Gambit, Fluent, Inc., Lebanon, NH, USA). Steady-state inspiratory laminar airflow at 15 L/min was calculated using commercial CFD software (FIDAP, Fluent, Inc., Lebanon, NH, USA). Streamline patterns, velocities, and helicity values were compared. In all subjects, the majority of flow passed through the middle and ventral regions of the nasal passages; however, the amount and location of swirling flow differed among individuals. Cross-sectional flow allocation analysis also indicated inter-individual differences. Laboratory water–dye experiments confirmed streamlines and velocity magnitudes predicted by the computational model. These results suggest that significant inter-individual differences exist in bulk airflow patterns in the nose.     

Malignant Lymphomas of the Nasal Cavity and Paranasal Sinuses: A Clinicopathologic and lmmunohistochemical Study

The clinicopathologic and immunohistological features of 20 Japanese patients with non-Hodgkin's lymphomas (NHLs) limited to the sinonasal area were studied using a broad panel of T- and B cell markers on paraffin-embedded and fresh frozen tissue. All cases showed a diffuse growth pattern. Nine cases were B cell lymphomas (immunoblas-tic n = 4, centroblastic n = 3, immunocytoma n = l, centrocytic n = l), and nine were T-cell lymphomas (pleomorphic medium and large cell n = 8, angioimmuno-blastic n = 1). In two cases, the cell lineage could not be determined. No morphologic features of angiocentric/an-giodestructive lymphoproliferative lesions or lymphoepithe-lial lesions in ductal or glandular epithelium were seen in our series. Eight (89%) of the nine T- cell tumors and four(44%) of the nine B - cell neoplasms involved both the nasal cavity and paranasal sinuses. Six of the nine T - cell neoplasms showed a clinical presentation of rhinitis, whereas all of the B - cell neoplasms showed tumor masses in the nasal cavity and/or paranasal sinuses. The two-year survival rate for T cell lymphomas was poorer than that for B-cell lymphomas. The five-year survival of patients with NHLs involving both the nasal cavity and paranasal sinuses was also poorer than that of patients in whom NHLs were limited to the nasal cavity. Acta Pathol Jpn 42 :333–338, 1992.