Surgical planning tool for robotically assisted hearing aid implantation

PURPOSE : For the facilitation of minimally invasive robotically performed direct cochlea access (DCA) procedure, a surgical planning tool which enables the surgeon to define landmarks for patient-to-image registration, identify the necessary anatomical structures and define a safe DCA trajectory using patient image data (typically computed tomography (CT) or cone beam CT) is required. To this end, a dedicated end-to-end software planning system for the planning of DCA procedures that addresses current deficiencies has been developed. METHODS :    Efficient and robust anatomical segmentation is achieved through the implementation of semiautomatic algorithms; high-accuracy patient-to-image registration is achieved via an automated model-based fiducial detection algorithm and functionality for the interactive definition of a safe drilling trajectory based on case-specific drill positioning uncertainty calculations was developed. RESULTS :    The accuracy and safety of the presented software tool were validated during the conduction of eight DCA procedures performed on cadaver heads. The plan for each ear was completed in less than 20 min, and no damage to vital structures occurred during the procedures. The integrated fiducial detection functionality enabled final positioning accuracies of [Formula: see text] mm. CONCLUSIONS :    Results of this study demonstrated that the proposed software system could aid in the safe planning of a DCA tunnel within an acceptable time.

Problems in the classical calculus of variations

This dissertation concerns convergence analysis for nonparametric problems in the calculus of variations and sufficient conditions for weak local minimizer of a functional for both nonparametric and parametric problems. Newton's method in infinite-dimensional space is proved to be well-defined and converges quadratically to a weak local minimizer of a functional subject to certain boundary conditions. Sufficient conditions for global converges are proposed and a well-defined algorithm based on those conditions is presented and proved to converge. Finite element discretization is employed to achieve an implementable line-search-based quasi-Newton algorithm and a proof of convergence of the discretization of the algorithm is included. This work also proposes sufficient conditions for weak local minimizer without using the language of conjugate points. The form of new conditions is consistent with the ones in finite-dimensional case. It is believed that the new form of sufficient conditions will lead to simpler approaches to verify an extremal as local minimizer for well-known problems in calculus of variations.

Reading on LCD vs e-Ink displays: effects on fatigue and visual strain

Purpose:  Most recently light and mobile reading devices with high display resolutions have become popular and they may open new possibilities for reading applications in education, business and the private sector. The ability to adapt font size may also open new reading opportunities for people with impaired or low vision. Based on their display technology two major groups of reading devices can be distinguished. One type, predominantly found in dedicated e-book readers, uses electronic paper also known as e-Ink. Other devices, mostly multifunction tablet-PCs, are equipped with backlit LCD displays. While it has long been accepted that reading on electronic displays is slow and associated with visual fatigue, this new generation is explicitly promoted for reading. Since research has shown that, compared to reading on electronic displays, reading on paper is faster and requires fewer fixations per line, one would expect differential effects when comparing reading behaviour on e-Ink and LCD. In the present study we therefore compared experimentally how these two display types are suited for reading over an extended period of time. Methods:  Participants read for several hours on either e-Ink or LCD, and different measures of reading behaviour and visual strain were regularly recorded. These dependent measures included subjective (visual) fatigue, a letter search task, reading speed, oculomotor behaviour and the pupillary light reflex. Results:  Results suggested that reading on the two display types is very similar in terms of both subjective and objective measures. Conclusions:  It is not the technology itself, but rather the image quality that seems crucial for reading. Compared to the visual display units used in the previous few decades, these more recent electronic displays allow for good and comfortable reading, even for extended periods of time.

Three-dimensional electron beam dose calculations

The MDAH pencil-beam algorithm developed by Hogstrom et al (1981) has been widely used in clinics for electron beam dose calculations for radiotherapy treatment planning. The primary objective of this research was to address several deficiencies of that algorithm and to develop an enhanced version. Two enhancements have been incorporated into the pencil-beam algorithm; one models fluence rather than planar fluence, and the other models the bremsstrahlung dose using measured beam data. Comparisons of the resulting calculated dose distributions with measured dose distributions for several test phantoms have been made. From these results it is concluded (1) that the fluence-based algorithm is more accurate to use for the dose calculation in an inhomogeneous slab phantom, and (2) the fluence-based calculation provides only a limited improvement to the accuracy the calculated dose in the region just downstream of the lateral edge of an inhomogeneity. The source of the latter inaccuracy is believed primarily due to assumptions made in the pencil beam's modeling of the complex phantom or patient geometry.^ A pencil-beam redefinition model was developed for the calculation of electron beam dose distributions in three dimensions. The primary aim of this redefinition model was to solve the dosimetry problem presented by deep inhomogeneities, which was the major deficiency of the enhanced version of the MDAH pencil-beam algorithm. The pencil-beam redefinition model is based on the theory of electron transport by redefining the pencil beams at each layer of the medium. The unique approach of this model is that all the physical parameters of a given pencil beam are characterized for multiple energy bins. Comparisons of the calculated dose distributions with measured dose distributions for a homogeneous water phantom and for phantoms with deep inhomogeneities have been made. From these results it is concluded that the redefinition algorithm is superior to the conventional, fluence-based, pencil-beam algorithm, especially in predicting the dose distribution downstream of a local inhomogeneity. The accuracy of this algorithm appears sufficient for clinical use, and the algorithm is structured for future expansion of the physical model if required for site specific treatment planning problems. ^

An evaluation of the personal response system program for the elderly in Harris County, Texas

The Personal Response System Program at Huffington Center on Aging, Baylor College of Medicine, provides emergency call systems for elderly people living independently in Houston, Texas. The goal of the project was to complete a formative evaluation of the Personal Response System Program. The specific aims of the evaluation were three-fold. One aim was to evaluate participant health status and level of disability. The second aim was to develop a health care cost estimation strategy. Finally, a preliminary cost-effectiveness analysis was completed to evaluate the program's impact on health care costs and health status among the elderly target population. ^ The evaluation was a longitudinal, randomized experimental design. After the screening of 120 volunteers for eligibility, clients were asked to complete a written questionnaire and a monthly health service contact diary. Volunteers were contacted by telephone interviewers to collect health status information from 100 eligible clients (83%) on three occasions during the six months of follow-up. ^ Initially, volunteers were randomized to two experimental groups. The two groups were found to be comparable at the beginning of the study. No significant differences were detected related to health status, level of disability, or history of physician visits at baseline. However, the group with the Personal Response System (PRS) device had more adverse health events, higher IADL scores, more frequent use of walkers, lower average health status scores, and fewer community volunteers hours than the usual care comparison group. ^ The health care costs were estimated based on an algorithm adapted from the American Medical Association guidelines. Average total health care costs for the group with the PRS device ($912) were greater than the usual care group ($464). However, median health care values for the PRS group ($263) were similar to the usual care comparison group ($234). The preliminary findings indicated that the use of the PRS device was not associated with health care cost savings. ^ In the preliminary cost-effectiveness analysis, use of the personal response system was found to be associated with increased mental health status among elderly clients. The cost-effectiveness evaluation indicated that the associated cost for six months was $710 per unit increase in mental component score when the $150 PRS subscription was included. However, clients with the PRS device were found to have a greater decline in physical health status during the six-month follow-up. The beneficial effect on mental health status was found to be in contrast to negative findings associated with changes in physical health status. The implications for future research relate to the need to identify risk factors among geriatric populations to better target groups that would most likely benefit from PRS Program enrollment. ^

Emergence of acquired HIV-1 drug resistance has almost been stopped in Switzerland - a 15 year prospective cohort analysis

BACKGROUND  Drug resistance is a major barrier to successful antiretroviral treatment (ART). Therefore, it is important to monitor time trends at a population level. METHODS  We included 11,084 ART-experienced patients from the Swiss HIV Cohort Study (SHCS) between 1999 and 2013. The SHCS is highly representative and includes 72% of patients receiving ART in Switzerland. Drug resistance was defined as the presence of at least one major mutation in a genotypic resistance test. To estimate the prevalence of drug resistance, data for patients with no resistance test was imputed based on patient's risk of harboring drug resistant viruses. RESULTS  The emergence of new drug resistance mutations declined dramatically from 401 to 23 patients between 1999 and 2013. The upper estimated prevalence limit of drug resistance among ART-experienced patients decreased from 57.0% in 1999 to 37.1% in 2013. The prevalence of three-class resistance decreased from 9.0% to 4.4% and was always <0.4% for patients who initiated ART after 2006. Most patients actively participating in the SHCS in 2013 with drug resistant viruses initiated ART before 1999 (59.8%). Nevertheless, in 2013, 94.5% of patients who initiated ART before 1999 had good remaining treatment options based on Stanford algorithm. CONCLUSION  HIV-1 drug resistance among ART-experienced patients in Switzerland is a well-controlled relic from the pre-combination ART era. Emergence of drug resistance can be virtually stopped with new potent therapies and close monitoring.

Ideología étnica durante el período amarniano : ¿límite o contacto con la otredad?

Durante el Reino Nuevo se produjo una ampliación de las fronteras y una fuerte centralización y estabilidad interna; es insoslayable resaltar al respecto el control por parte de la monarquía de los territorios conquistados y el mantenimiento de su posición en el Levante mediterráneo frente a la presión de mitanios e hititas. Particularmente, nos centraremos en el período amarniano, que tradicionalmente ha tenido una visión peyorativa basada en el supuesto de la 'incapacidad' real de intervención en asuntos políticos, como así también las grandes 'dificultades' en mantener el efectivo dominio del territorio.Sin embargo, diversos fueron los mecanismos de legitimación desarrollados por el poder regio en este contexto. Centrándonos en la postura fenomenológico-hermenéutica del historiador de las religiones rumano Mircea Eliade (1957) y basándonos también en los aportes de Fredrik Barth (1976), Jan Assmann (2005) y Pascal Vernus (2011), será nuestro objetivo analizar las implicaciones simbólico-religiosas de la concepción egipcia de los pueblos extranjeros y de las interacciones políticas con ellos bajo el período de gobierno de Akhenatón.

Ideología étnica durante el período amarniano : ¿límite o contacto con la otredad?

Durante el Reino Nuevo se produjo una ampliación de las fronteras y una fuerte centralización y estabilidad interna; es insoslayable resaltar al respecto el control por parte de la monarquía de los territorios conquistados y el mantenimiento de su posición en el Levante mediterráneo frente a la presión de mitanios e hititas. Particularmente, nos centraremos en el período amarniano, que tradicionalmente ha tenido una visión peyorativa basada en el supuesto de la 'incapacidad' real de intervención en asuntos políticos, como así también las grandes 'dificultades' en mantener el efectivo dominio del territorio.Sin embargo, diversos fueron los mecanismos de legitimación desarrollados por el poder regio en este contexto. Centrándonos en la postura fenomenológico-hermenéutica del historiador de las religiones rumano Mircea Eliade (1957) y basándonos también en los aportes de Fredrik Barth (1976), Jan Assmann (2005) y Pascal Vernus (2011), será nuestro objetivo analizar las implicaciones simbólico-religiosas de la concepción egipcia de los pueblos extranjeros y de las interacciones políticas con ellos bajo el período de gobierno de Akhenatón.

Ideología étnica durante el período amarniano : ¿límite o contacto con la otredad?

Durante el Reino Nuevo se produjo una ampliación de las fronteras y una fuerte centralización y estabilidad interna; es insoslayable resaltar al respecto el control por parte de la monarquía de los territorios conquistados y el mantenimiento de su posición en el Levante mediterráneo frente a la presión de mitanios e hititas. Particularmente, nos centraremos en el período amarniano, que tradicionalmente ha tenido una visión peyorativa basada en el supuesto de la 'incapacidad' real de intervención en asuntos políticos, como así también las grandes 'dificultades' en mantener el efectivo dominio del territorio.Sin embargo, diversos fueron los mecanismos de legitimación desarrollados por el poder regio en este contexto. Centrándonos en la postura fenomenológico-hermenéutica del historiador de las religiones rumano Mircea Eliade (1957) y basándonos también en los aportes de Fredrik Barth (1976), Jan Assmann (2005) y Pascal Vernus (2011), será nuestro objetivo analizar las implicaciones simbólico-religiosas de la concepción egipcia de los pueblos extranjeros y de las interacciones políticas con ellos bajo el período de gobierno de Akhenatón.

Road environment modeling using robust perspective analysis and recursive Bayesian segmentation

Recently, vision-based advanced driver-assistance systems (ADAS) have received a new increased interest to enhance driving safety. In particular, due to its high performance–cost ratio, mono-camera systems are arising as the main focus of this field of work. In this paper we present a novel on-board road modeling and vehicle detection system, which is a part of the result of the European I-WAY project. The system relies on a robust estimation of the perspective of the scene, which adapts to the dynamics of the vehicle and generates a stabilized rectified image of the road plane. This rectified plane is used by a recursive Bayesian classi- fier, which classifies pixels as belonging to different classes corresponding to the elements of interest of the scenario. This stage works as an intermediate layer that isolates subsequent modules since it absorbs the inherent variability of the scene. The system has been tested on-road, in different scenarios, including varied illumination and adverse weather conditions, and the results have been proved to be remarkable even for such complex scenarios.

How can video analysis help laparoscopic surgeons?

Automatic analysis of minimally invasive surgical (MIS) video has the potential to drive new solutions that alleviate existing needs for safer surgeries: reproducible training programs, objective and transparent assessment systems and navigation tools to assist surgeons and improve patient safety. As an unobtrusive, always available source of information in the operating room (OR), this research proposes the use of surgical video for extracting useful information during surgical operations. Methodology proposed includes tools' tracking algorithm and 3D reconstruction of the surgical field. The motivation for these solutions is the augmentation of the laparoscopic view in order to provide orientation aids, optimal surgical path visualization, or preoperative virtual models overlay

Rebalancing urban mobility: a tale of four cities

The key of mobility in urban planning is not in dispute. Integrated strategies that take into account the interrelations among land use, transport supply and demand and the different transportation modes are more necessary than ever. In Europe, regulatory tools such as local mobility plans or traffic plans have been enforced for a long time, evolving into so-called sustainable urban transport plans (SUTP) ? that is, plans thatmerge urban planning,mobility governance, social awareness and environmental safeguards to develop a vision based on sustainability and equity. Indeed, SUTP are aimed at solving typical problems in current land use, such as urban sprawl, which make clear the need for a paradigm shift from transport (or mobility) planning to land use (or city) planning, thereby producing urban mobility plans that are fully aligned with integrated urban development plans. This paper describes how SUTP are articulated across Europe according to four case studies: Peterborough (UK), Chambe¿ry (France), Ferrara (Italy) and Pinto (Spain), to highlight variations and commonalities, both among the four national legal frameworks and the actual planning processes at the local level. Objectives, measures and indicators used in the monitoring and evaluation phases have been analysed and the results assessed. The main conclusion of the paper is that, as seen in these real-life examples, the lack of integration between spatial planning and transport strategies results in the unsustainability of urban areas and, therefore, in a significant loss of competitiveness.

Super-Resolution in Respiratory Synchronized Positron Emission Tomography

Respiratory motion is a major source of reduced quality in positron emission tomography (PET). In order to minimize its effects, the use of respiratory synchronized acquisitions, leading to gated frames, has been suggested. Such frames, however, are of low signal-to-noise ratio (SNR) as they contain reduced statistics. Super-resolution (SR) techniques make use of the motion in a sequence of images in order to improve their quality. They aim at enhancing a low-resolution image belonging to a sequence of images representing different views of the same scene. In this work, a maximum a posteriori (MAP) super-resolution algorithm has been implemented and applied to respiratory gated PET images for motion compensation. An edge preserving Huber regularization term was used to ensure convergence. Motion fields were recovered using a B-spline based elastic registration algorithm. The performance of the SR algorithm was evaluated through the use of both simulated and clinical datasets by assessing image SNR, as well as the contrast, position and extent of the different lesions. Results were compared to summing the registered synchronized frames on both simulated and clinical datasets. The super-resolution image had higher SNR (by a factor of over 4 on average) and lesion contrast (by a factor of 2) than the single respiratory synchronized frame using the same reconstruction matrix size. In comparison to the motion corrected or the motion free images a similar SNR was obtained, while improvements of up to 20% in the recovered lesion size and contrast were measured. Finally, the recovered lesion locations on the SR images were systematically closer to the true simulated lesion positions. These observations concerning the SNR, lesion contrast and size were confirmed on two clinical datasets included in the study. In conclusion, the use of SR techniques applied to respiratory motion synchronized images lead to motion compensation combined with improved image SNR and contrast, without any increase in the overall acquisition times.

Surface velocity and ice discharge of the ice cap on King George Island, Antarctica

Glaciers on King George Island, Antarctica, have shown retreat and surface lowering in recent decades, concurrent with increasing air temperatures. A large portion of the glacier perimeter is ocean-terminating, suggesting possible large mass losses due to calving and submarine melting. Here we estimate the ice discharge into the ocean for the King George Island ice cap. L-band synthetic aperture radar images covering the time-span January 2008 to January 2011 over King George Island are processed using an intensity-tracking algorithm to obtain surface velocity measurements. Pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field. Ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data. The maximum ice surface speeds reach mayor que 225 m/yr, and the total ice discharge for the analysed flux gates of King George Island is estimated to be 0.720+/-0.428 Gt/yr, corresponding to a specific mass loss of 0.64+/-0.38 m w.e./yr over the area of the entire ice cap (1127 km2).

Estudio numérico de flujo turbulento cargado con partículas sólidas a través de canales y tuberías de sección variable

La presente Tesis Doctoral tiene como objetivo el estudio de flujo turbulento cargado con partículas sólidas a través de canales y tuberías de sección constante usando un enfoque Euleriano-Lagrangiano. El campo de flujo de la fase de transporte (aire) se resuelve usando simulación de grandes escalas (LES), implementada en un programa de volúmenes finitos mientras que las ecuaciones gobernantes de la fase dispersa son resueltas por medio de un algoritmo de seguimiento Lagrangiano de partículas que ha sido desarrollado y acoplado al programa que resuelve el flujo. Se estudia de manera sistemática y progresiva la interacción fluido→partícula (one-way coupling), a través de diferentes configuraciones geométricas en coordenadas cartesianas (canales de sección constante y variable) y en coordenadas cilíndricas (tuberías de sección constante y sección variable) abarcando diferentes números de Reynolds y diferentes tamaños de partículas; todos los resultados obtenidos han sido comparados con datos publicados previamente. El estudio de flujo multifásico a través de, tuberías de sección variable, ha sido abordada en otras investigaciones mayoritariamente de forma experimental o mediante simulación usando modelos de turbulencia menos complejos y no mediante LES. El patrón de flujo que se verifica en una tubería con expansión es muy complejo y dicha configuración geométrica se halla en múltiples aplicaciones industriales que involucran el transporte de partículas sólidas, por ello es de gran interés su estudio. Como hecho innovador, en esta tesis no solo se resuelven las estadísticas de velocidad del fluido y las partículas en tuberías con diferentes tamaños de expansión y diferentes regímenes de flujo sino que se caracteriza, usando diversas formulaciones del número de Stokes y el parámetro de arrastre, el ingreso y acumulación de partículas dentro de la zona de recirculación, obteniéndose resultados coincidentes con datos experimentales. ABSTRACT The objective of this Thesis research is to study the turbulent flow laden with solid particles through channels and pipes with using Eulerian-Lagrangian approach. The flow field of the transport phase (air ) is solved using large eddy simulation ( LES ) implemented in a program of finite volume while the governing equations of the dispersed phase are resolved by means of a particle Lagrangian tracking algorithm which was developed and coupled to principal program flow solver . We studied systematically and progressively the fluid interaction → particle ( one- way coupling ) , through different geometric configurations in Cartesian coordinates ( channel with constant and variable section) and in cylindrical coordinates ( pipes with constant section and variable section ) covering different Reynolds numbers and different particle sizes, all results have been compared with previously published data . The study of multiphase flow through, pipes with variable section has been addressed in other investigations predominantly experimentally or by simulation using less complex models and no turbulence by LES. The flow pattern is verified in a pipe expansion is very complex and this geometry is found in many industrial applications involving the transport of solid particles, so it is of great interest to study. As an innovator fact , in this Thesis not only finds fluid velocity statistics and particles with different sizes of pipe expansion and different flow regimes but characterized, using various formulations of the Stokes number and the drag parameter are resolved, the entry and accumulation of particles within the recirculation zone , matching results obtained with experimental data.