Stefan Reichling

Palpation imaging using a haptic system for virtual reality applications in medicine.

In the field of medical diagnosis, there is a strong need to determine mechanical properties of biological tissue, which are of histological and pathological relevance. Malignant tumors are significantly stiffer than surrounding healthy tissue. One of the established diagnosis procedures is the palpation of body organs and tissue. Palpation is used to measure swelling, detect bone fracture, find and measure pulse, or to locate changes in the pathological state of tissue and organs. Current medical practice routinely uses sophisticated diagnostic tests through magnetic resonance imaging (MRI), computed tomography (CT) and ultrasound (US) imaging. However, they cannot provide direct measure of tissue elasticity. Last year we presented the concept of the first haptic sensor actuator system to visualize and reconstruct mechanical properties of tissue using ultrasonic elastography and a haptic display with electrorheological fluids. We developed a real time strain imaging system for tumor diagnosis. It allows biopsies simultaneously to conventional ultrasound B-Mode and strain imaging investigations. We deduce the relative mechanical properties by using finite element simulations and numerical solution models solving the inverse problem. Various modifications on the haptic sensor actuator system have been investigated. This haptic system has the potential of inducing real time substantial forces, using a compact lightweight mechanism which can be applied to numerous areas including intraoperative navigation, telemedicine, teaching and telecommunication.

P1C-1 Evaluation of Material Parameters of PVA Phantoms for Reconstructive Ultrasound Elastography

The real-time ultrasound elastography system presented in Pesavento, A. et al., (1999) allows the use of elastography in a clinical study for the early detection of prostate cancer during conventional transrectal ultrasound examinations. Since tumors often consist of hard tissue structures, imaging the elastic properties promises to increase the ability to detect prostate cancer. In the frame of reconstructive elastography it is important to understand more about material properties and boundary conditions. Thus in freehand elastography, the compression is manually induced by the conducting physician leading to unstable strain image sequences. Therefore we present in this work a new designed phantom with known target E-modulus and boundary data to help physicians get used to real time elastography systems and to solve the forward and inverse problems respectively.

A New Haptic Sensor Actuator System for Virtual Reality Applications in Medicine

The pathological state of soft tissues is often correlated with changes in stiffness. Malignant tumors are significantly stiffer and more immobile than surrounding healthy tissue. (hard lesions, “nodes” in organs: tumors; calcifications in vessels: arteriosclerosis). The main problem is, that such information is usually not available or can only be obtained by manual palpation, which is subjective and limited in sensitivity. It requires intuitive assessment and does not allow quantitative documentation. On the one hand a suitable sensor is required for quantitative measurement of mechanical tissue properties. On the other hand, there is also a need for a realistic mechanical display of such tissue properties. Suitable actuator arrays with high spatial resolution acting in real time are required. A haptic sensor actuator system is presented in this paper including a sensitive sensor part and an actuator array for different applications. The mechanical consistency of an object is to be locally specified using a sensor system and represented perceptibly in a remote position on a tactile display (actuator system) for the user. The sensor system uses ultrasound (US) elastography, whereas the actuator array is based on electrorheological (ER) fluids.

P5D-6 Displacement Estimators Using Angular Insonifications for Reconstructive Elastography

In order to obtain quantitative mechanical properties of tissue non-invasively, we propose in this work an inverse approach by which the spatial distribution of the relative shear modulus of tissue can be estimated from the measured axial and lateral deformation using angular insonifications. Measurements on PVA phantoms and the procedure to obtain the shear modulus are described.

Entwicklung eines haptischen Sensor-Aktor-Systems für Anwendungen in der virtuellen Realität

Die mechanischen Eigenschaften des biologischen Gewebes stellen wichtige Diagnoseinformationen dar und sind von groser histologischer und pathologischer Bedeutung. Insbesondere Tumoren stel- len sich oft als Gewebeverhartungen dar. Das Problem ist, dass konven- tionelle bildgebende Verfahren (Ultraschall, Computertomographie, Ma- gnetresonanztomographie) oftmals keine pathologische Verhartungen im Gewebe (wie z. B. in Brust- oder Prostatakrebs) erkennen konnen. In diesem Projekt wird ein neuartiges System fur die Erfassung und Darstellung haptischer Informationen in der virtuellen Realitat entwickelt. Mit einem haptischen Sensor-Aktor-System soll die Konsistenz eines Objektes ortsaufgelost erfasst und an anderer Stelle fur den Benutzer tastbar dargestellt werden. Das haptische System wird als eine Technologieplattform angesehen, auf der anschliesend verschiedene Produkte fur die Medizintechnik, die Unter-haltungsindustrie oder den Ausbildungssektor entwickelt werden konnen.

A Haptic System for Virtual Reality Applications Based on Ultrasound Elastography and Electro-Rheological Fluids

Mechanical properties of biological tissue represent important diagnostic information and are of histological and pathological relevance. Malignant tumors are significantly stiffer and more immobile than surrounding healthy tissue. Hard calcifications in vessels occur due to arteriosclerosis. The problem is, that such information is usually not available or can only be obtained by manual palpation, which is subjective and limited in sensitivity. It requires intuitive assessment and does not allow quantitative documentation. Unfortunately, none of the established medical imaging equipment such as magnetic resonance imaging (MRI) or X-ray computed tomography (CT) can provide direct measure of tissue elasticity. On the one hand a suitable sensor is required for quantitative measurement of mechanical tissue properties. On the other hand there is also some need for a realistic haptic display of such tissue properties. Suitable actuator arrays with high spatial resolution acting in real time are required. A haptic sensor actuator system is presented in this paper including a sensitive sensor part and an actuator array for different applications. The mechanical consistency of an object is to be locally specified using a sensor system and represented perceptibly in a remote position on an actuator system for the user. The sensor system uses ultrasound (US) elastography, whereas the actuator array is based on electrorheological (ER) fluids.