3D-motion mapping of the malleus-incus complex using a robot-mounted optical coherence tomography vibrometry system.

BackgroundPrecise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers a high-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy.Aim of the workEvaluation of the use of fpVCTSECO in combination with an otosurgical planning software for a more accurate diagnosis and treatment of congenital aural atresia.Material and methodsSeven patients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering.ResultsImaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. A significant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D.DiscussionThe introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

HintergrundEine präzise präoperative radiologische Evaluation von Auralatresien ist für die Operationsplanung von größter Bedeutung. Bisher wurde hierfür die Multislice-Computertomographie (MSCT) verwendet, die jedoch kleine Strukturen wie den Stapes nur unzureichend dargestellen kann. Die „flat-panel volume CT“ (fpVCT) mit ihren sekundären Rekonstruktionen (fpVCTSECO) bietet eine hochauflösende Darstellung des Mittelohrs. Eine neue otochirurgische Planungssoftware ermöglicht überdies die detaillierte 3‑D-Rekonstruktion der Mittelohranatomie.Ziel der ArbeitEvaluierung des Einsatzes von fpVCTSECO in Kombination mit einer otochirurgischen Planungssoftware zur genaueren Diagnose und Behandlung kongenitaler Auralatresien.Material und MethodenSieben Patienten mit kongenitaler Auralatresie erhielten präoperativ ein MSCT (600 µm Schichtdicke) und ein korrespondierendes fpVCT (466 µm Schichtdicke). Zusätzlich wurden fpVCTSECO (99 µm Schichtdicke) rekonstruiert. Die Jahrsdoerfer- und Siegert-Grading-Scores wurden bestimmt und ihre Anwendbarkeit in den oben genannten bildgebenden Modalitäten bewertet. Zusätzlich wurde der Malleus-incus-Komplex im 3‑D-Rendering analysiert.ErgebnisseDie Bildgebung mit fpVCTSECO ermöglichte eine zuverlässige Darstellung der Anomalien, insbesondere der Gehörknöchelchenkette. Es wurde ein signifikanter Unterschied im Siegert-Grading-Score festgestellt. Zusätzlich konnte der Malleus-Incus-Komplex in 3‑D besser dargestellt werden.DiskussionDie Einführung neuer bildgebender Verfahren und chirurgischer Planungstechniken in das diagnostische Konzept der Auralatresie erleichtert die Identifizierung der fehlgebildeten Anatomie und ermöglicht eine systematische Analyse. Diese Kombination kann auch dazu beitragen, die Pathologie genauer zu klassifizieren und damit die Sicherheit und den Erfolg des chirurgischen Eingriffs zu erhöhen.

Tympanic-membrane and malleus–incus-complex co-adaptations for high-frequency hearing in mammals

Imaging depth-resolved birefringence and optic axis orientation with polarization sensitive optical coherence tomography (PS-OCT) unveils details of tissue structure and organization that can be of high pathophysiologic, mechanistic, and diagnostic value. For catheter-based PS-OCT, the dynamic rotation of the fiber optic probe, in addition to the polarization effects of the system components, complicates the reliable and robust reconstruction of the sample's optic axis orientation. Addressing this issue, we present a new method for the reconstruction of absolute depth-resolved optic axis orientation in catheter-based PS-OCT by using the intrinsic retardance of the protecting catheter sheath as a stable guide star signal. Throughout the paper, we rigorously inspect the retardance and optic axis orientation of the sheath and validate our method by imaging a birefringent phantom with known optic axis orientation. Reconstructing the optic axis orientation of the phantom, placed at different locations around the catheter, we measured an average absolute deviation (AAD) for the mean optic axis orientation over cross-sectional images of 3.28°, even with significant bending stress on the catheter. This corresponds to an almost three-fold improvement compared to our earlier method (optic axis AAD of 9.41°). We finally highlight the capability of our reconstruction with stereotactic catheter-based PS-OCT of a fresh sheep brain.

Classical Russian S-5-S pendulum seismometer was modified for recording of the rotational components of ground motion. This seismometer was used for monitoring of mining induced seismic events in the Karviná region (Czech Republic). Together, three translational components of ground vibration velocity and one rotational component of ground vibration velocity around the vertical axis were recorded. Elaborated mining induced seismic events with epicentral distances up to 9 km were recorded in Doubrava locality, where the exploitation of black coal is still active. Numerical study of measured component attributes of mining induced seismic events is presented in this paper, namely squared Morlet wavelet coefficients and squared coherence spectrum between rotational and translational components. Squared Morlet wavelet coefficients enable to analyse time-and-frequency structure of elaborated signal, e.g. dynamics of the onset, evolution and disappearance of typical periods of the harmonic peaks, etc. Spectral measure of coherence was applied here for investigation of synchronization effects in 2-dimensional time series of translational and rotational components.

Light refraction from a uniaxial crystal with arbitrary optic axis orientation using matrix representation

SummaryBackgroundMiddle ear surgery techniques can improve hearing destroyed by disease, but results of treatment are difficult to predict. Therefore, researchers use a Laser Doppler Vibrometer to measure vibrations of human middle ear ossicles.Material/MethodsMeasurements of ossicular chain vibrations are performed on fresh human temporal bone specimens using Laser Doppler Vibrometer. Vibrations of stapes are recorded in 3 cases: 1) for intact ossicular chain, 2) when incus long process is removed, and 3) after long process reconstruction with bone cement. A typical analysis of transfer function is completed by other methods applied in dynamics.ResultsMeasurements and analysis of stapes vibrations in case of intact and damaged ossicular chain show regular and irregular behavior which can be recognize with the help of phase portraits, recurrence plots, correlation dimension, and Hurst and Lyapunov exponents. The long process reconstruction with bone cement gives good results in improving hearing.ConclusionsRecurrence plots, and Lyapunov and Hurst exponents used in the study complete information obtained from transfer function and can be employed to enrich the classical approach to ossicular chain vibrations.

We present a generalized analysis of fiber-based polarization-sensitive optical coherence tomography with an emphasis on determination of sample optic axis orientation. The polarization properties of a fiber-based system can cause an overall rotation in a Poincaré sphere representation such that the plane of possible measured sample optic axes for linear birefringence and diattenuation no longer lies in the QU-plane. The optic axis orientation can be recovered as an angle on this rotated plane, subject to an offset and overall indeterminacy in sign such that only the magnitude, but not the direction, of a change in orientation can be determined. We discuss the accuracy of optic axis determination due to a fundamental limit on the accuracy with which a polarization state can be determined as a function of signal-to-noise ratio.

The Casimir force is calculated in the configuration of two parallel plates separated by an anisotropic media. The result exhibits a dependence on the orientation of the optical axis of the intervening media. It is possible that the Casimir force switches its direction as the optical axis orientation varies. The greatest magnitude of the force could be achieved at any optical axis orientation, depending on the dielectric properties of the plates and the intervening media. A comparison between the relativistic and nonrelativistic result revealed that the nonrelativistic approximation could significantly underestimate the attraction or overestimate the repulsion. This error was even greater when the optical axis of the intervening media was perpendicular to the surface of the plates. The nonrelativistic approximation might even fail to predict the trends of the Casimir force at small distances.

Bone is a complex natural material that presents many challenges to researchers interested in characterizing its mechanical properties. There are different techniques, such as drying, embalming, and freezing, to preserve bones for engineering and scientific study. There are advantages and disadvantages to these techniques, and there have been limited studies comparing the effect of preservation techniques on the mechanical and fracture properties. In this research, aged and fresh bovine bone specimens are tested in compression while monitoring acoustic emissions (AE). Three main aspects of testing are investigated: the force-displacement curves, acoustic emission activity, and fracture patterns observed in X-ray computed tomography (CT) scans. Before compression testing, the ends of each bone specimen were potted in epoxy, CT scanned, encased in heat-shrink plastic, and an acoustic emission sensor was mounted to each specimen. During compression testing, force-displacement data is collected and synchronized to acoustic emission data. The tested bone specimen were CT scanned. Pre-test CT scans showed that aged bones contained fractures that were produced by the aging (bleaching and boiling) processes. Aged bone specimens had higher failure forces and higher apparent stiffness values. The force-displacement curves show that aged bone specimens have a more brittle behavior. Aged bone specimens had greater numbers of acoustic emission events than fresh bone specimens. The AE events in fresh bone specimens were associated with lower energy and higher average frequencies. Acoustic emission events occur in aged bone specimens well before they occur in fresh bone specimens. In some instances, no acoustic emission event occurred until failure in fresh bone specimens. Post-test CT scans revealed that aged bone specimens had large multifragmentary fractures that propagated through the entire length of the specimen. The fractures produced in fresh bone specimens were contained within the lower and upper twenty percent of the specimen. The fresh bone specimens had circumferential fractures that were not observed in the aged bone specimens. These fractures were contained between the inner and outer dense cortical bone veneer of the specimens. The data generated and presented show there is a clear difference in the behavior of aged and fresh bone specimens. These differences are demonstrated by force-displacement curves, acoustic emission data, and fracture types identified in CT scans. Deformation properties between fresh and aged bone specimens presented a clear distinction between the microcracks and crack propagation between fresh and aged bones. Overall, each aspect of this research showed clear differences in the failure behavior of fresh and aged bones. Although aged bone specimens and fresh bone specimens have less stringent handling and storage requirements than fresh bone specimens, these two specimen types have different mechanical and fracture properties.

Polarization-sensitive optical coherence tomography (PS-OCT) is widely used to image fibrous biological tissues, providing additional image contrast compared to intensity-based OCT, including birefringence and optic axis orientation information. Here a theoretical and experimental analysis of the effect of the system fiber on determination of sample optic axis orientation using a previously reported algorithm based on the angle between Stokes vectors on the Poincaré sphere in fiber-based PS-OCT experimentally confirms that the algorithm only works correctly when the parameters of the system fiber are kept constant during the imaging acquisition of each frame. To extend the use of the algorithm to situations in which the parameters of the system fiber are varied among A-scans or image frames, which is true when the OCT probe scanning does move the sample arm fiber, we propose the use of polarization maintaining fiber (PMF) with a special polarization axis orientation as the sample arm fiber for extracting sample optic axis orientation using fiber-based PS-OCT systems. The use of the PMF makes the system insensitive to variations of the sample fiber birefringence for determining optic axis orientation by automatically removing the offset ambiguity from each A-scan. We demonstrated by using a computer evaluation model that the proposed method is capable of extracting the relative optic axis orientation correctly when the PMF birefringence is varied among A-scans due to external disturbances to the system fiber, provided that the polarization axis orientation (slow or fast) of the PMF is kept constant during the measurement.

The finite-difference in the frequency domain (FD-FD) method is formulated to study the dispersion characteristics of anisotropic dielectric waveguides with their optical axes not aligned with the coordinate system axes. In this analysis the optical axes are initially assumed to be aligned with the coordinate system axes such that the electric permittivity and magnetic permeability tensors are diagonal. The optical axes of the anisotropic dielectric are then rotated an angle /spl theta/ (or /spl phi/) with respect to the coordinate system axes. While the FD-FD method developed is general, it is applied here only to waveguides containing uniaxial anisotropic dielectrics. The results show that accurate optical axis orientation is important in the design of dielectric waveguides.

Imaging the human body is the most important diagnostic tool in healthcare. Therefore, there is an endless need for improvement of imaging techniques. In this thesis, an extension of a medical imaging technique is further developed to provide extra image contrast based on polarization-changing properties of the tissue. This technique, called polarization-sensitive optical coherence tomography (PS-OCT), is an extension of optical coherence tomography (OCT), which is often used in ophthalmology to create high resolution images of the retina of the human eye. Retinal imaging is the main application of PS-OCT chosen for this thesis. Extra image contrast in PS-OCT includes imaging of birefringence, depolarization, and optic axis of the tissue. An in-house built PS-OCT setup is presented and improved. This setup is then used throughout the thesis to create 3D in vivo retinal images of healthy volunteers and patients. Improvements of PS-OCT data analysis are presented and demonstrated in healthy volunteers. A new imaging metric, optic axis uniformity (OAxU), is introduced. OAxU is defined as the length of the spatially averaged optic axis and varies between 0 and 1. Differential Mueller matrix calculations have been implemented and improved to visualize birefringent structures and their optic axes locally. A deep-learning model is developed as a tool to segment the PS-OCT images. Improvement of PS-OCT analysis allows for orientation images of the collagen in the peripapillary sclera, revealing a radially oriented fiber layer preceding a circumferentially orientated fiber layer. Close to the optic nerve head (ONH), the circumferentially oriented layer displaces the radially oriented fiber layer. PS-OCT is used to image patients with high myopia, glaucoma, osteogenesis imperfecta (OI) or wet age-related macular degeneration (wAMD) to compare the visualization of these new findings in ocular fibrillar architecture to healthy volunteers. These diseases are relevant for PS-OCT imaging to detect changes in scleral collagen, damage to the RNFL, or subretinal fibrosis. Multiple parameters are investigated in this study, including birefringence of the sclera and its correlation with axial length, orientations of RNFL in glaucoma patients, dimensions of the circularly oriented sclera (COS) ring, and thickness of the radially oriented sclera (ROS) layer. The ROS is thinner in myopia patients and OI patients. Besides a thinner ROS layer, birefringence of the sclera was lower in OI patients. Fibrosis can be detected and its orientation can be determined in 3D in AMD patients. Fibrosis shows a higher organization than expected and was often observed in large patches of similar orientations which can vary in depth. The applicability of (PS-)OCT goes beyond ophthalmology. In this thesis, it is investigated whether PS-OCT would be valuable in the imaging of airway. Multiple diseased lungs and healthy lungs are imaged ex vivo to investigate differences in alveoli size/presence and ASM thickness. Optic axis orientation images proved very useful to discriminate different birefringent structures, which is not possible in standard OCT imaging. This allowed for automatic ASM segmentation which is relevant for diseases were this layer is thickened such as asthma, fibrotic sarcoidosis (FS), and fibrotic hypersensitivity pneumonitis (fHP).

ABSTRACTOptical anisotropy of sapphire have been studied by both polarized Raman scattering and transmission variable angle spectroscopic ellipsometry (TVASE). The polarized Raman effect was measured on both c-plane (0001) and a-plane (2110) sapphire substrates. Two TO phonons (379 and 431 cm−l) and four LO phonons (418, 450, 577, and 750 cm−1) were observed when the optical axis <c> is perpendicular to the polarization of the incident laser beam (for both c-plane and a-plane). While only two TO phonons (379 and 431cm−1) and two LO phonons (418 and 645 cm−1) can be seen when the optical axis is parallel to the polarization for an a-plane sapphire. The optical axis of the a-plane sapphire can then be quickly determined by either maximizing or minimizing the 645 LO peak intensity with about ±10° error. TVASE measurements were carried out in the energy range of 0.75eV to 5.8eV at room temperature. Sizable off-diagonal Jones matrix elements Apst, and Aspt can be detected even with the optical axis 1° off the X-axis. This indicates that TVASE has a high sensitivity to optical anisotropy. By minimizing these off-diagonal elements and combining the Raman analysis, the optical axis orientation of an a-plane or m-plane (0110) sapphire can therefore be fully determined with an error of less than 1°.

Metoda oceny ruchomości kosteczek słuchowych. Badanie eksperymentalne i możliwe zastosowanie kliniczne