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Hold the Phone
Published in Kenneth L. Mossman, Radiation Risks in Perspective, 2006
The recent debate on acoustic neuroma and cell phones illustrates how difficult it is to establish proof of risk. A small Swedish study reports increased risks of acoustic neuroma associated with cell phone use of at least 10 years duration.10 The study reports that acoustic neuroma (a rare benign, noncancerous growth that arises from the vestibulocochlear nerve in the brain) appears to occur predominantly on the side of the head that is more frequently associated with cell phone use.11 Health effects would be expected to predominate on the ipsilateral side of the head because radiation exposures are higher there. Further, risks were observed only for cell phone use in excess of 10 years. Individuals who used cell phones for less than 10 years did not show elevated risk. In contrast a Danish study found no correlation between pattern of cell phone use and frequency of acoustic neuroma. The results of this prospective population-based nationwide study that included a large number of long-term cell phone users suggest no radiogenic risk.12 Currently there are few studies large enough to allow for a definitive conclusion about a long-term risk of acoustic neuroma. To confirm causality, further research is needed to elucidate mechanisms of radiogenic acoustic neuroma and to confirm the Swedish finding that brain lesions occur on the same side of the head as cell phone use. Whatever the risk, many people would consider the benefits of cell phones to be too important to abandon them. If the risk of acoustic neuroma turns out to be important, technological modifications in cell phones could be made to reduce exposures and thus reduce risks.
E
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[acoustics, biomedical, general] Biological sensing device that can acquire pressure waves (i.e., sound). The ear has several structural components as well as various functional components. Structurally, the ear is divided in three segments: the outer ear, the middle ear, and the inner ear. The outer ear is the exterior shell (pinna) with magnified areal size in comparison to the auditory meatus or ear canal to ensure effective and high probability of collecting large magnitude pressure waves that captures the pressure waves and guides them into the auditory canal leading to the middle ear. At the middle ear, the pressure variations are transferred into mechanical vibrations of a solid. The middle ear is separated from the auditory canal by the tympanic membrane or ear drum the tympanic membrane is the percussion device that converts pressure variations into mechanical vibrations, facilitating further transfer to a liquid-filled sensory compartment (inner ear). Inside the middle ear, the tympanic membrane pushes against a lever system of three interlocking bones (the ossicles) to transfer the mechanical vibrations to the oval window of the inner ear. The bone structure components are (moving inward, respectively) the malleus (hammer), connected to the incus (anvil) connected to the stapes (stirrup), which is connected to the oval window. The middle ear is generally pressure stabilized by maintaining contact with the external pressure through the Eustachian tube, which connects to the nasal cavity. The sound intensity transferred in the middle ear is capable of being regulated by various means. The intrinsic regulation of energy transfer is in the aspect ratio of the components. Primarily, the elasticity of the tympanic membrane can be controlled by pressure variations of the middle ear mediated by the Eustachian tube. The vibration magnitude is controlled by spacing the three bones through muscular interaction (for instance, the malleus is attached to the tensor tympani muscle), providing a means to control the loudness of the sound as well as offering protection from mechanical damage to the inner ear. The oval window is the passage to the inner ear, which consists of the cochlea. The cochlea doubles back to the final window, the round window, close to the oval window in the middle ear. The inner workings of the cochlea are described in detail in the entry for cochlea. The intricate mechanism of conversion of mechanical vibrations to electrical impulses is transmitted over the cochlear branch of the vestibulocochlear nerve for data acquisition and signal processing by the brain (also seehearing). In addition to hearing, the inner ear also has a construction attached that functions as a means to detect and preserve equilibrium (see Figure E.2).
Hearing loss, lead (Pb) exposure, and noise: a sound approach to ototoxicity exploration
Published in Journal of Toxicology and Environmental Health, Part B, 2018
Krystin Carlson, Richard L. Neitzel
The largest area of concern and variation with epidemiologic study methodology was the varying quality and type of hearing examinations. Good hearing requires a functional outer, middle, and inner ear, and unimpeded transmission of neural signals from the vestibulocochlear nerve, through the brainstem, to the primary auditory cortex in the cerebral cortex of the brain. An important need for both toxicological and epidemiological studies is to examine the location and mechanism of hearing damage due to Pb exposure, and its interaction with noise. For example, while noise-induced damage typically manifests as cochlear hair cell death in the basal region, the toxicological studies suggest damage due to Pb takes place in the neural processing networks. Without this knowledge, the optimal measure (or measures) of hearing is unclear.
Semi-automatic 3D reconstruction of middle and inner ear structures using CBCT
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2023
Florian Beguet, Thierry Cresson, Mathieu Schmittbuhl, Cédric Doucet, David Camirand, Philippe Harris, Jean-Luc Mari, Jacques de Guise
To obtain precise modelling of the structures of the inner and middle ear, a segmentation step is necessary to extract and label these structures from CBCT images. The segmentation step is challenging (Beucher and Lantuéjoul 1979; Kass et al. 1988; Osher and Sethian 1988; Yoo et al. 2000, 2001; Pohle and Toennies 2001; Xianfen et al. 2005; Noble et al. 2009, 2011; Bradshaw et al. 2010; Poznyakovskiy et al. 2013; Cerrolaza et al. 2014; Ruiz Pujadas et al. 2016; Zhu et al. 2017) especially because these structures are linked together, as illustrated by the 3D models in the Figure 1d. The structures of the middle ear are characterised by the same bone nature but a variable bone density (Greef et al. 2015), demonstrating a certain range of intensities in CBCT imaging. The depiction of the border of these structures can thus be very challenging, especially for the incudomalleolar joint (blue arrow in Figure 1b) and the suspensory ligaments of the ossicular chain (cyan arrow in Figure 1b). The middle ear is not a completely closed structure, as it presents two windows: the round window sealed by the secondary tympanic membrane; and the oval window, which is in direct contact with the stapes (green arrows in Figure 1a–c). Moreover, the vestibulocochlear nerve emerging directly from the inner ear presents quite the same level of density as the chamber of the vestibule and the spirally coiled cochlea (red arrows in Figure 1a). In addition, the segmentation of these very small and complex structures presents some specific challenges: The shape of the inner ear is topologically complex: the cochlea is a snail-shaped object and the semi-circular canals correspond to 3D objects characterized by a surface of genus 3 (Figure 1a). The preservation of these complex features during the process of segmentation of the inner ear remains a difficult challenge.The stapes is a very fine structure of genus 1, and it is 3 mm wide and 4 mm high with a diameter of approximately 0.4 mm for the crus (Figure 1c) (Farahani and Nooranipour 2008). This creates great difficulties for the depiction of its limits considering that the spatial resolution of the CBCT images is 0.15 mm; only its curvature is indeed detectable at the interface of the oval window(green arrow in Figure 1a–c).