Registration of a Validated Mechanical Atlas of Middle Ear for Surgical Simulation

International audienceThis paper is centered on the development of a new train- ing and rehearsal simulation system for middle ear surgery. First, we have developed and validated a mechanical atlas based on finite element method of the human middle ear. The atlas is based on a microMRI. Its mechanical behavior computed in real-time has been successfully val- idated. In addition, we propose a method for the registration of the mechanical atlas on patient imagery. The simulation can be used for a rehearsal surgery with the geometrical anatomy of a given patient and with mechanical data that are validated. Moreover, this process does not necessitate a complete re-built of the model

An international review of laser Doppler vibrometry:Making light work of vibration measurement

© 2016 In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments

Large-volume optical coherence tomography with real-time correction of geometric distortion artifacts

Large-volume optical coherence tomography (OCT)-setups employ scanning mirrors and suffer from non-linear geometric distortion artifacts in which the degree of distortion is determined by the maximum angles over which the mirrors rotate. In this chapter, we describe a straightforward approach to correct for these distortion artifacts, creating an alternative to previously reported ray-tracing schemes that are unable to apply these corrections in real-time. By implementing the proposed 3D recalibration algorithm on the graphics card of a standard computer, this feature can be applied in real-time. We validate the accuracy of the technique using OCT measurements of a highly curved object within a large imaging volume of 12.35 x 10.13 x 2.36 mm3. The resulting 3D object shape measurements are compared against high-resolution and aberration-free optical profilometry measurements. Maintaining an optical resolution of <10μm within the sample, both axially and transversally, we realized a real-time, high-resolution, largevolume OCT imaging system, capable of producing distortion corrected wide-field OCT data with a geometric surface shape accuracy of <15μm. © 2013 Nova Science Publishers, Inc. All rights reserved

Real-time correction of geometric distortion artefacts in large-volume optical coherence tomography

Large-volume optical coherence tomography (OCT) setups employ scanning mirrors and suffer from geometric distortion artefacts in which the degree of distortion is determined by the maximum angles over which the mirrors rotate. In this note, we describe a straightforward coordinate transformation scheme to correct for these artefacts in three dimensions, creating an alternative to previously reported ray-tracing schemes. We demonstrate that this recalibration procedure can be applied in real time by implementing the proposed algorithm on the graphics card of a standard computer, making it useful for topography applications. The accuracy of the proposed calibration procedure is validated over an imaging volume of 12.35x10.13x2.36 mm3 using optical moire measurements of a highly curved object. © 2013 IOP Publishing Ltd

Full-field thickness distribution of human tympanic membrane obtained with optical coherence tomography

The full-field thickness distribution, three-dimensional surface model and general morphological data of six human tympanic membranes are presented. Cross-sectional images were taken perpendicular through the membranes using a high-resolution optical coherence tomography setup. Five normal membranes and one membrane containing a pathological site are included in this study. The thickness varies strongly across each membrane, and a great deal of inter-specimen variability can be seen in the measurement results, though all membranes show similar features in their respective relative thickness distributions. Mean thickness values across the pars tensa ranged between 79 and 97 μm; all membranes were thinnest in the central region between umbo and annular ring (50-70 μm), and thickness increased steeply over a small distance to approximately 100-120 μm when moving from the central region either towards the peripheral rim of the pars tensa or towards the manubrium. Furthermore, a local thickening was noticed in the antero-inferior quadrant of the membranes, and a strong linear correlation was observed between inferior-posterior length and mean thickness of the membrane. These features were combined into a single three-dimensional model to form an averaged representation of the human tympanic membrane. 3D reconstruction of the pathological tympanic membrane shows a structural atrophy with retraction pocket in the inferior portion of the pars tensa. The change of form at the pathological site of the membrane corresponds well with the decreased thickness values that can be measured there. © 2013 Association for Research in Otolaryngology

Determination of stratospheric component behaviour using Finite Element model updating

Abstract: In general, it is difficult to analyse equipment for space applicability due to the fact that realistic tests on Earth are technically difficult and expensive. To prove the reliability of space systems, a combination of numerical analysis and expensive pre-flight tests is used. However, this paper discusses a new methodology in which a combination is made of low-budget ground tests with a newly developed finite element model updating technique which can deliver a time efficient added value or alternative to the expensive and time-consuming pre-flight tests during thermal analysis. In addition, this contribution shows the influence of several design parameters on the accuracy of thermal simulations for space applications and discusses how this accuracy can be optimised. The methodology is verified within the HACORD project of the REXUS/BEXUS programme. (C) 2016 Elsevier Masson SAS. All rights reserved