Mechanics of the Middle Ear

背景资料：中耳由三块骨头（锤骨、砧骨和镫骨）组成，它们通过韧带悬挂在头部充满空气的空腔中，并由两块肌肉（镫骨肌和鼓膜张肌）作用。鼓膜将中耳与耳道分开，并连接到锤骨。计算机模型增强了我们对中耳生物力学的理解。然而，目前的模型不能用于模拟高强度的声音和镫骨肌的反射性收缩。计算机模型的扩展对于诊断、辅助和保护装置的工程和设计是重要的。 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。 目的：（1）在有和没有肌肉收缩的情况下测量中耳骨和鼓膜的振动;（2）测量由肌肉收缩引起的中耳几何形状的变化;（3）开发用于从图像构建计算机模型的软件;（4）估计用于模型的适当材料属性;（5）通过将模拟数据与测量数据进行比较来测试模型;以及（6）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计测量尸体耳朵的鼓膜和中耳骨的振动。肌肉收缩将使用定制硬件进行。我们将使用显微成像技术，在有和没有肌肉收缩的情况下，对中耳几何结构的变化进行成像。为了从医学图像自动生成计算机模型的几何形状，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特性的参数，以使模拟结果与测量的选定部分相匹配，并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细化模型。然后，将使用改进的模型来模拟声反射测试，其中施加强烈的声音以收缩镫骨肌。通过系统地改变模型的参数和几何形状，我们将了解中耳几何形状和病理学如何影响声反射测试。 影响：我们将为生物医学工程专业的学生提供严格的培训，使他们具有高度的就业能力。我们将率先（1）测量在有和没有肌肉收缩的情况下对高强度声音的响应振动，（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，我们还将开发自动建模软件。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.