Volume 85, Issue 5 - Themenschwerpunkt: IEEE Workshop on Industrial and Medical Measurement and Sensor Technology – SENSORICA 2017

The analysis and investigation of flow processes is a key task in many science and engineering disciplines. In this context, optical diagnostic methods represent versatile tools that allow the determination of concentration, temperature, and flow velocity fields. However, most of the established tools are based on complicated and expensive equipment including advanced laser sources and specialized cameras. In the present work, an alternative approach employing low-cost components in terms of a commercial light-emitting diode (LED) and a webcam is demonstrated. A single experimental setup for emission, absorption, and schlieren imaging has been assembled. Proof-of-concept measurements were carried out in flames and a liquid mixing process. Two-color pyrometry of the thermal radiation from soot particles was used for planar thermometry in a candle flame. Schlieren imaging was employed to visualize the refractive index and hence the temperature gradient in a premixed welding torch butane/air flame. LED-absorption imaging was used to study the mixing of ink and water. In conclusion, this work demonstrates that advanced flow diagnostics can be performed at low cost, which is of particular interest in teaching and training, where expensive equipment may not be available.

Ultrasound solutions are widely used in industrial and medical applications for distance measurements and imaging. A multiplexing switch unit is required to drive a piezoelectric transducer array for imaging by a single ultrasound pulse source. Higher frequencies are required for better image resolution. The necessary multiplexer has to handle these high driving voltages up to 100 V at high frequencies up to 100 MHz. The test environment and methodology for semiconductor multiplexer circuits are described in this article. The main focus is set on the generation of large test signals needed to drive the multiplexer.

Exposimetry of electromagnetic fields refers to a measurement technology aiming to quantify the immission or absorption of fields and/or energy in specific ranges of the electromagnetic spectrum. Portable, small and accurate measurement instruments were developed to provide tools for epidemiological research and environmental monitoring. The target measurement quantity was the average amount of RMS field strength that an average individual will experience in everyday environments. This quantity can be used to classify different groups of the population or to track changes in exposure conditions within defined regions or along specified tracks. Methods and tools for the assessment of the personal exposure to low-frequency magnetic fields (LF-MF), radio frequency electromagnetic fields (RF-EMF) and pulsed RF emissions from radar installations have been developed, characterized, and tested. The result is a measurement platform enabling a large variety of measurement procedures and study protocols.

Using the OpenSim software and verified anatomical data, a computer model for the calculation of biomechanical parameters is developed and used to determine the effect of a reattachment of the Supraspinatus muscle with a medial displacement of the muscle attachment point, which may be necessary for a rupture of the supraspinatus tendon. The results include the influence of the operation on basic biomechanical parameters such as the lever arm, as well as the calculated the muscle activations for the supraspinatus and deltoid. In addition, the influence on joint stability is examined by an analysis of the joint reaction force. The study provides a detailed description of the used model, as well as medical findings to a reattachment of the supraspinatus.

Particularly multiparous elderly women may suffer from vaginal vault prolapse after hysterectomy due to weak support from lax apical ligaments. A decreased amount of estrogen and progesterone in older age is assumed to remodel the collagen thereby reducing tissue stiffness. Sacrocolpopexy is either performed as open or laparoscopic surgery using prosthetic mesh implants to substitute lax ligaments. Y-shaped mesh models (DynaMesh, Gynemesh, and Ultrapro) are implanted in a 3D female pelvic floor finite element model in the extraperitoneal space from the vaginal cuff to the first sacral (S1) bone below promontory. Numerical simulations are conducted during Valsalva maneuver with weakened tissues modeled by reduced tissue stiffness. Tissues are modeled as incompressible, isotropic hyperelastic materials whereas the meshes are modeled either as orthotropic linear elastic or as isotropic hyperlastic materials. The positions of the vaginal cuff and the bladder base are calculated from the pubococcygeal line for female pelvic floor at rest, for prolapse and after repair using the three meshes. Due to mesh mechanics and mesh pore deformation along the loaded direction, the DynaMesh with regular rectangular mesh pores is found to provide better mechanical support to the organs than the Gynemesh and the Ultrapro with irregular hexagonal mesh pores.

We report on the suitability of two different ranges of Hounsfield units (HU) in computed tomography (CT) for the quantification of metallic components of active implantable medical devices (AIMD). The conventional Hounsfield units (CHU) range, which is traditionally used in radiology, is well suited for tissue but suspected inappropriate for metallic materials. Precise HU values are notably beneficial in radiotherapy (RT) for accurate dose calculations, thus for the safety of patient carrying implants. Some of today’s CT machines offers an extended Hounsfield units (EHU) range. This study presents CT acquisitions of a water phantom containing various metallic discs and an implantable-cardioverter defibrillator (IPG). We show that the comparison of HU values at EHU and CHU ranges clearly reveals the superiority and accuracy of EHU. Some geometrical discrepancies perpendicular to slices are observed. At EHU metal artifact reduction algorithms (MAR) underestimates HU values rendering MAR potentially inappropriate for RT.

In this paper we present novel solutions to support the application of computer assisted surgical interventions in which optical surgical navigation systems based on stereo cameras are used. The objective is to improve both the pre-operative setup and the intra-operative use of the navigation system. Following a short introduction describing the potential for improvements of existing navigation systems new approaches and the components to implement them are described. The pre-operative alignment of the stereo camera is made easier by attaching a small graphic display to its tripod which can show how much of the operating area is covered by the measurement volume of the camera. The intra-operative application is improved by a mechanism for motorized camera motions in order to follow the position of surgical instruments. Furthermore a small display can be attached to a surgical instrument which clearly indicates to the surgeon how to guide the instrument in order to stay on the planned trajectory.

A miniaturized implantable multi-sensor system for cardiovascular monitoring of physiological parameters is presented. High accuracy pressure measurements within the vessel can be performed by a capacitive pressure sensor. Additional information about the patient, e. g., sudden movement, inclination or increased temperature can be obtained by additional sensor components such as an acceleration sensor and a temperature sensor unit. This information facilitates compensation of interferences for more accurate pressure measurements. A multi-functional ASIC enables, amongst others, sensor signal processing, power management and telemetric communication with extracorporeal electronics. Sensor chips, the multi-functional ASIC and passive components are assembled on a LTCC circuit board in which an antenna coil is integrated for telemetric energy and data transmission at a frequency of 13.56 MHz. In order to support further miniaturization, the implant shall be encapsulated with a stack of very thin and hermetic ceramics applied by ALD instead of using bulky metal housings. Further encapsulation with polymers, which can be functionalised with appropriate biomolecules, is necessary for a proper shape, a biocompatible interface to the surrounding tissue and, thereby, reduction of thrombogenicity.

Wearable devices that monitor our vital signs have been gaining more importance with each year. Non-invasive, continuous, accurate and precise blood pressure assessment method integrated in a wearable is a multidisciplinary challenge. This work presents an electrical bioimpedance (EBI) unit for multi-frequency measurements on pulsating artery for central aortic pressure (CAP) estimation. The developed device provides low complexity in the electronics design with a frequency range between 1 kHz and 200 kHz. It is able to register the impedance of blood vessel volume change simultaneously at different locations. Experiments were carried out in vivo by using the four-electrode configuration on human thorax, axillary artery and radial artery. Preliminary results show the applicability of the proposed impedance spectroscopy system to measure blood vessel volume changes. The impedance data can be later interpreted into the aortic blood pressure wave by using a generalized transfer function. In addition, experimental test-phantom and electrode design are introduced for testing purposes of the impedance system.