Mechanics of the Middle Ear

背景：中耳由三块骨头组成的链状结构(锤骨、砧骨、胫骨和距骨)，它们由韧带悬挂在头部一个充满空气的空腔中，并由两块肌肉--砧骨肌和鼓室张肌--作用。鼓膜将中耳与耳道分开，并与锤骨相连。通过计算机模型，我们对中耳生物力学的理解得到了加强。然而，目前的模型不能用来模拟高强度的声音和腓肠肌的反射性收缩。计算机模型的扩展对于诊断、辅助和防护设备的工程和设计非常重要。*假设：在计算机模型中包含适当的材料属性将允许扩展到高强度声音。*目标：(1)测量有或没有肌肉收缩的中耳骨和鼓膜的振动；(2)测量肌肉收缩引起的中耳几何形状的变化；(3)开发从图像构建计算机模型的软件；(4)估计模型中使用的适当材料属性，并通过将模拟与测量数据进行比较来测试模型；和(5)演示模型的应用。*方法：我们将使用最先进的激光多普勒振动仪测量身体耳朵的鼓膜和中耳骨的振动。肌肉收缩将使用定制的硬件进行应用。我们将使用显微成像技术对有和没有肌肉收缩的中耳几何形状的变化进行成像。为了从医学图像中自动生成计算机模型的几何图形，我们将使用现代数字图像处理方法。将通过优化模型来估计指定建模组织的材料属性的参数，从而使模拟结果与所选部分的测量相匹配，并且将通过将模拟结果与未用于参数估计的数据进行比较来测试改进的模型。然后，改进后的模型将被用来模拟声学反射测试，在该测试中，应用强烈的声音来收缩腓骨肌。通过系统地改变模型的参数和几何形状，我们将加深对中耳几何形状和病理如何影响声反射测试的理解。*影响：我们将为生物医学工程专业的学生提供严格的培训，使他们具有很高的就业能力。我们将率先(1)测量有或没有肌肉收缩的高强度声音的振动，(2)使用显微成像来测量肌肉收缩引起的几何变化，(3)开发和验证对强烈声音有效的计算机模型，以及(4)模拟声反射测试。此外，我们还将开发用于自动建模的软件。我们的软件、模型和测量验证数据将提供给听力生物力学研究社区。*

Background: The middle ear consists of a chain of three bones (malleus, incus, and stapes) that are suspended by ligaments in an air-filled cavity in the head and are acted upon by two muscles, the stapedius and tensor tympani. The eardrum separates the middle ear from the ear canal and is connected to the malleus. Our understanding of the middle ear's biomechanics has been enhanced by computer models. However, current models cannot be used to simulate high intensity sounds and reflexive contraction of the stapedius muscle. Extension of computer models is important for the engineering and design of diagnostic, assistive and protective devices.***Hypothesis: The inclusion of appropriate material properties in computer models will allow the extension to high intensity sounds.***Objectives: (1) Measure vibrations of the middle-ear bones and eardrum with and without muscle contractions; (2) measure changes in middle-ear geometry caused by muscle contraction; (3) develop software for constructing computer models from images; (4) estimate appropriate material properties for use in models and and test the models by comparing simulations to measured data; and (5) demonstrate the application of the models.***Approach: We will measure vibrations of the eardrum and middle-ear bones in cadaveric ears using a state-of-the-art laser Doppler vibrometer. Muscle contractions will be applied using custom-built hardware. We will image changes in middle-ear geometry with and without muscle contractions using micro-imaging techniques. To automatically generate the geometry of computer models from medical images, we will use modern digital image processing methods. Parameters specifying the material properties of the modeled tissues will be estimated by optimizing the model so simulation results match a select portion of the measurements, and the refined models will be tested by comparing simulation results to data not used for parameter estimation. The refined models will then be using to simulate the acoustic reflex test in which an intense sound is applied to contract the stapedius muscle. By varying the parameters and geometry of the model systematically, we will develop an understanding of how middle ear geometry and pathology affect the acoustic reflex test.***Impact: We will provide rigorous training to biomedical engineering students that will make them highly employable. We will be the first to (1) measure vibrations in response to high intensity sounds with and without muscle contractions, (2) use micro-imaging to measure geometric changes caused by muscle contractions, (3) develop and validate computer models that are valid for intense sounds, and (4) simulate the acoustic reflex test. Additionally, we will develop software for automatic model construction. Our software, models and measured validation data will be made available to the hearing biomechanics research community.*********