Forward model for quantitative pulse-echo speed-of-sound imaging

Computed ultrasound tomography in echo mode (CUTE) allows determining the spatial distribution of speed-of-sound (SoS) inside tissue using handheld pulse-echo ultrasound (US). This technique is based on measuring the changing phase of beamformed echoes obtained under varying transmit (Tx) and/or receive (Rx) steering angles. The SoS is reconstructed by inverting a forward model describing how the spatial distribution of SoS is related to the spatial distribution of the echo phase shift. CUTE holds promise as a novel diagnostic modality that complements conventional US in a single, real-time handheld system. Here we demonstrate that, in order to obtain robust quantitative results, the forward model must contain two features that were not taken into account so far: a) the phase shift must be detected between pairs of Tx and Rx angles that are centred around a set of common mid-angles, and b) it must account for an additional phase shift induced by the error of the reconstructed position of echoes. In a phantom study mimicking liver imaging, this new model leads to a substantially improved quantitative SoS reconstruction compared to the model that has been used so far. The importance of the new model as a prerequisite for an accurate diagnosis is corroborated in preliminary volunteer results

On flow properties, fibre distribution, fibre orientation and flexural behaviour of FRC

For improving the mechanical properties of fibre reinforced concrete one can either increase the fibre content, use hybrid fibre systems, or one can attempt to align fibres in the direction of stress. In this paper, it is attempted to use the flow-properties of the fresh (self-compacting) concrete to change the fibre distribution and orientation. Using a single mixture of fibre reinforced concrete, containing 3% of 30mm long straight steel fibres, the fibre distribution and orientation was determined in three different parts of a ‘U-shaped specimen' where the concrete could flow in three different directions. The fibre distribution and orientation was determined from a CT-scan. Flexural tests show that the mechanical behaviour depends on the fibre distribution and orientation, which can be affected by changing the viscosity of the fresh mixtur

Pulse-echo speed-of-sound imaging using convex probes.

Computed ultrasound tomography in echo mode (CUTE) is a new ultrasound (US)-based medical imaging modality with promise for diagnosing various types of disease based on the tissue's speed of sound (SoS). It is developed for conventional pulse-echo US using handheld probes and can thus be implemented in state-of-the-art medical US systems. One promising application is the quantification of the liver fat fraction in fatty liver disease. So far, CUTE was using linear array probes where the imaging depth is comparable to the aperture size. For liver imaging, however, convex probes are preferred since they provide a larger penetration depth and a wider view angle allowing to capture a large area of the liver. With the goal of liver imaging in mind, we adapt CUTE to convex probes, with a special focus on discussing strategies that make use of the convex geometry in order to make our implementation computationally efficient. We then demonstrate in an abdominal imaging phantom that accurate quantitative SoS using convex probes is feasible, in spite of the smaller aperture size in relation to the image area compared to linear arrays. A preliminary in vivo result of liver imaging confirms this outcome, but also indicates that deep quantitative imaging in the real liver can be more challenging, probably due to the increased complexity of the tissue compared to phantoms

Analysis of pressure drop and blast pressure leakage of passive air blast safety valves : an experimental and numerical study

The purpose of passive air blast safety valves is to protect people and technical installations in buildings or facilities. In case of explosions, e.g. due to technical failures in an oil- and gas refinery, the safety valve should close in milliseconds with the incident shock wave and substantially reduce the blast-pressure leakage into the building. On the other hand, the safety valve should exhibit a low pressure drop in normal operation in order to reduce the power consumption of the ventilators. One main difficulty in the design of such safety valves is to meet the minimum technical requirements, while ensuring the functionality in intrinsically different operating modes. Therefore, the present study proposes a target-oriented evaluation and optimization procedure for such devices, incorporating comprehensive numerical and experimental investigations. CFD, FEM and FSI analyses are regarded as an appropriate approach to predict valve performance parameters and to gain additional insights into the flow or structural behavior of the safety valve, which serves then as a basis for geometrical optimizations. The introduced procedure is exemplified on an existing passive air blast safety valve as a case study. The performance of the new design is significantly increased in ventilation operation, while meeting the performance criteria in the stress case when subjected to blast loads

A Living Cell Repository of the Cranio-/Orofacial Region to Advance Research and Promote Personalized Medicine

The prevalence of congenital anomalies in newborns is estimated to be as high as 6%, many of which involving the cranio-/orofacial region. Such malformations, including several syndromes, are usually identified prenatally, at birth, or rarely later in life. The lack of clinically relevant human cell models of these often very rare conditions, the societal pressure to avoid the use of animal models and the fact that the biological mechanisms between rodents and human are not necessarily identical, makes studying cranio-/orofacial anomalies challenging. To overcome these limitations, we are developing a living cell repository of healthy and diseased cells derived from the cranio-/orofacial region. Ultimately, we aim to make patient-derived cells, which retain the molecular and genetic characteristics of the original anomaly or disease in vitro, available for the scientific community. We report our efforts in establishing a human living cell bank derived from the cranio-/orofacial region of otherwise discarded tissue samples, detail our strategy, processes and quality checks. Such specific cell models have a great potential for discovery and translational research and might lead to a better understanding and management of craniofacial anomalies for the benefit of all affected individuals

Bayesian Approach for a Robust Speed-of-Sound Reconstruction Using Pulse-Echo Ultrasound

Computed ultrasound tomography in echo mode (CUTE) is a promising ultrasound (US) based multi-modal technique that allows to image the spatial distribution of speed of sound (SoS) inside tissue using hand-held pulse-echo US. It is based on measuring the phase shift of echoes when detected under varying steering angles. The SoS is then reconstructed using a regularized inversion of a forward model that describes the relation between the SoS and echo phase shift. Promising results were obtained in phantoms when using a Tikhonov-type regularization of the spatial gradient (SG) of SoS. In-vivo, however, clutter and aberration lead to an increased phase noise. In many subjects, this phase noise causes strong artifacts in the SoS image when using the SG regularization. To solve this shortcoming, we propose to use a Bayesian framework for the inverse calculation, which includes a priori statistical properties of the spatial distribution of the SoS to avoid noise-related artifacts in the SoS images. In this study, the a priori model is based on segmenting the B-Mode image. We show in a simulation and phantom study that this approach leads to SoS images that are much more stable against phase noise compared to the SG regularization. In a preliminary in-vivo study, a reproducibility in the range of 10 ms -1 was achieved when imaging the SoS of a volunteer's liver from different scanning locations. These results demonstrate the diagnostic potential of CUTE for example for the staging of fatty liver disease

NeoMap App Reloaded

Mit der rasanten Verbreitung von Smartphones nehmen auch Karten-Applikationen einen immer wichtigeren Standpunkt im Alltag ein. Dies nicht zuletzt dank des allseits bekannten und sehr verbreiteten Google Map Apps, welches auf diversen Plattformen verfügbar ist. Im Gegensatz zu Google Maps stellt der Kartendienst OpenStreetMap Kartenmaterial bereit, welches für jedermann frei verwendbar und auch zur konsequenten Offline-Nutzung verfügbar ist. Nebst lizenztechnischen Nachteilen bietet Google Maps auch keine Möglichkeit, eigene Karten, welche zuvor geolokalisiert wurden, einzubinden. Mit dem Projekt NeoMap, welches am Institut für Software der HSR ins Leben gerufen wurde, wird das Ziel verfolgt, eine vollständige offline-fähige Karten-Applikation auf der Basis von Android und OpenStreetMap zu entwickeln. Diese soll es dem Benutzer unter anderem ermöglichen, eigene geolokalisierte Karten einzubinden. Um hierbei eine möglichst leistungsfähige Lösung zu bieten, wird auf die hochperformante Grafikbibliothek OpenGL ES zur Darstellung der Karte gesetzt. Eine erste Version der App wurde bereits in einer Semesterarbeit entwickelt. Der Fokus dieser Bachelorarbeit lag darin, die bestehende Version des NeoMap Apps zu überarbeiten und auf den neusten Stand der Technik zu bringen. Die Migration betraf vorwiegend die Umstellung von OpenGL ES 1.1 auf die Version 2.0 sowie die Verwendung des modernen Android 4.0 API. Ein weiteres Hauptziel war es, die schlecht wart- und erweiterbare App zurück auf einen guten Stand zu bringen. Um dieses Ziel zu erreichen, wurde ein grosses Refactoring durchgeführt. Nachdem diese erste Phase erfolgreich abgeschlossen werden konnte, wurde die Applikation um weitere nützliche Features ergänzt, welche die Attraktivität der App weiter steigern sollen. Dazu gehören unter anderem eine 3D-Schrägansicht als Orientierungshilfe, das Erfassen von Notizen in Form von Punkten oder Routen auf der Karte sowie eine Geonamen-Suche. Bei all diesen Aspekten wurde der Grundvorsatz der Offline-Fähigkeit immer eingehalten