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首页> 外文学位 >The human carotid bulb as a hemodynamic volume flow rate pulsatility damping filter mediated by carotid bifurcation vessel luminal geometry.
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The human carotid bulb as a hemodynamic volume flow rate pulsatility damping filter mediated by carotid bifurcation vessel luminal geometry.

机译：人颈动脉作为通过颈动脉分叉血管腔几何学介导的血流动力学体积流量脉动阻尼过滤器。

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摘要

This research hypothesized that the carotid bifurcation bulb is a hemodynamic volume flow rate, pulsatility damping, low-pass filter. It was also hypothesized that bifurcation vessel lumen geometry mediated this "smoothing" process.;Non-invasive, cardiac-gated, magnetic resonance pulse sequences were used to acquire both structural (2D-TOF pulse sequence) and hemodynamic flow quantification (phase contrast pulse sequence) data. A final test population comprising 46 normal individuals (15 females, 31 males, ages between 20 and 60 years) resulted in 92 carotid bifurcations.;The structural image sets were post-processed to yield two-dimensional geometric measurements representing three defined structural classes: integral (global) structure, confluence (local), and carotid bulb (local) geometry. Additionally, the resulting hemodynamic flow quantification data were used to compute both time domain (volume flow rate (VFR) waveforms, pulsatility/smoothing indices) and frequency domain (bulb and non-bulb-related) transfer functions. Statistical analysis used three data classes: general patient data, geometric and hemodynamic. The results indicated significant relationships within and between each class. Finally, each bifurcation was classified using a simple ordered, primary geometric parameter system.;Two pulsatility smoothing effects were evident. Effect 1: as the bifurcation index value increased, smoothing increased and only bulb-related transfer function magnitude and phase values showed low-pass filtering effects (magnitude decreases: 2--3 Hz., phase difference increases: 2 Hz.). Effect 2: as the bulb inlet diameter increased, smoothing increased and only bulb-related transfer function magnitude and phase values showed low-pass filtering effects (magnitude decreases: 2--3 Hz., phase angle increases: 3 Hz.). Thus, two geometric parameters mediated overall, simultaneous smoothing effects in a linear manner: the bifurcation index (globally) and the bulb inlet diameter (locally).;A fluid mechanics vascular impedance model accounted for the contrasting smoothing effects observed. The local bulb mechanism emphasizes the inductive and capacitive components of vascular impedance due to the bulb's complex geometry and increased distensibility. The global bifurcation smoothing mechanism emphasizes the non-frequency resistance component of vascular impedance (Poiseiulle resistances)---the compliance and inductive forces were considered insignificant. This above model accounts for the effects seen.;Therefore, the global (anatomically integral) mechanism sets the level of naturally-occurring pulsatility for the entire bifurcation, while the carotid bulb simultaneously applies low-pass filtering, smoothing the internal carotid arterial flow only.
机译：这项研究假设颈动脉分叉球是一种血流动力学体积流量，脉动阻尼，低通滤波器。还假设分叉血管腔的几何结构介导了这种“平滑”过程。非侵入性，心动门控，磁共振脉冲序列用于获取结构性（2D-TOF脉冲序列）和血流动力学定量（相衬脉冲）序列）数据。最终的测试人群包括46位正常个体（15位女性，31位男性，年龄在20至60岁之间）导致了92个颈动脉分叉。;对结构图像集进行后处理以产生代表三个定义的结构类别的二维几何测量值：整体（整体）结构，汇合（局部）和颈动脉（局部）几何形状。此外，所得的血流动力学流量量化数据可用于计算时域（体积流率（VFR）波形，脉动/平滑指数）和频域（灯泡和非灯泡相关）传递函数。统计分析使用了三种数据类别：一般患者数据，几何和血液动力学。结果表明每个班级之间和班级之间存在重要关系。最后，使用简单的有序的，主要的几何参数系统对每个分叉进行分类。显而易见，两个脉动平滑效果。效果1：随着分叉指数值的增加，平滑度增加，并且只有与灯泡相关的传递函数幅度和相位值显示出低通滤波效果（幅度减小：2--3 Hz。相位差增大：2 Hz）。效果2：随着灯泡入口直径的增加，平滑度增加，并且只有与灯泡相关的传递函数幅度和相位值才显示出低通滤波效果（幅度减小：2--3 Hz。相角增大：3 Hz）。因此，两个几何参数以线性方式介导了总体的同时平滑效果：分叉指数（全局）和灯泡入口直径（局部）。流体力学血管阻抗模型解释了所观察到的对比平滑效果。由于灯泡的复杂几何形状和扩展性，局部灯泡机制强调了血管阻抗的电感性和电容性成分。全局分叉平滑机制强调了血管阻抗的非频率电阻分量（Poiseiulle电阻）-顺应性和感应力被认为是微不足道的。上面的模型解释了所看到的效果。因此，整体（解剖学上的整体性）机制设定了整个分叉处自然发生的搏动的水平，而颈动脉同时应用了低通滤波，仅使内部颈动脉血流平滑。

著录项

  • 作者

    Hisley, Kenneth Calvin.;

  • 作者单位

    University of Maryland, Baltimore.;

  • 授予单位 University of Maryland, Baltimore.;
  • 学科 Morphology.;Medical imaging.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 494 p.
  • 总页数 494
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;
  • 关键词

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