Miniaturized force/torque sensor for in vivo measurements of tissue characteristics.

This paper presents the development of a surgical instrument to measure interaction forces/torques with organic tissue during operation. The focus is on the design progress of the sensor element, consisting of a spoke wheel deformation element with a diameter of 12 mm and eight inhomogeneous doped piezoresistive silicon strain gauges on an integrated full-bridge assembly with an edge length of 500 µm. The silicon chips are contacted to flex-circuits via flip chip and bonded on the substrate with a single component adhesive. A signal processing board with an 18 bit serial A/D converter is integrated into the sensor. The design concept of the handheld surgical sensor device consists of an instrument coupling, the six-axis sensor, a wireless communication interface and battery. The nominal force of the sensing element is 10 N and the nominal torque is 1 N-m in all spatial directions. A first characterization of the force sensor results in a maximal systematic error of 4.92 % and random error of 1.13 %.

Characteristic of a force sensing guide wire for minimally invasive cardiac surgery.

In minimal invasive cardiac surgery (MICS), the surgeon is missing haptic feedback of the guide wire for navigation through the vessels. A wide range of guide wires with various properties and performance characteristics are available to reduce the risk of complications during the intervention. This paper presents a force sensing guide wire for cardiac catheterization, which provides the surgeon a haptic feedback on the guide wire tip. Three conventional wires for the recanalization of chronic total coronary occlusions (CTO) are investigated and general design requirements for the force sensing guide wire are determined. A comparison of the developed with the conventional guide wires concerning the tip force is conducted. The measured tip force of the force sensing guide wire is 50 mN, which is slightly lower than two of the compared conventional wires. As a result, the guide wire offers a good compromise between a soft, low-traumatic and hard guide wire tip.

[Methods of resolution for haptic assistance during catheterization]. / Lösungsansätze für haptische Assistenz bei Katheterisierungen.

During catheterization navigation within the patient is mainly dependent on a live x-ray image on the screen. Although methods for 3D visualisation and remote navigation of the catheter are discussed and tested still precise positioning is merely the result of intense training and a high skill and level of training of the performing surgeon. This article refers to a system which can be considered as an add-on for existing procedures of catheterization. It compromises of a miniaturised force sensor located at the tip of guide-wires whose prototype is shown here. The measured forces will be presented to the surgeon amplified by an external actuator described in this article. As a result a haptic perception of the forces between the tip of the guide-wire and the vessels walls will be available and enable the surgeon to gain an impression which is comparable to palpation of living vessels from the inside

[Telemetric system for measuring the pressure of the tongue on the palate]. / Telemetrisches Messsystem zur Bestimmung des Druckes der Zunge gegen den Gaumen.

The development of the upper jaw during growth is influenced by the function and position of the tongue and perioral soft tissues, and the pressures exerted by them. Accurate determination of the forces exerted by the tongue would provide relevant information about this influence. To date, our ability to obtain continuous recordings of the tongue pressure during certain functions is limited. In this paper, an easy-to-employ and accurate telemetric system for such functional measurements is presented. The system, consisting of four piezoresistive pressure sensors, a microcontroller, a telemetric module and batteries, is integrated within a removable orthodontic plate and transmits the measured data out of the oral cavity to a receiver.

[Piezoresistive sensors for medical applications exemplified by a probe for measure pressure in the rectum]. / Piezoresistive Sensoren für medizinische Anwendungen am Beispiel einer Sonde zur Druckmessung im Enddarm.

We described a pressure sensor probe suitable for assessing dynamic rectal pressure profiles. It comprises 10 piezoresistive sensors mounted in low-temperature co-fired ceramic. To protect against corrosion, the sensors are coated with a biocompatible silicone elastomer. The ceramic measures 4.5 x 5.5 x 1.4 mm. The entire probe has a diameter of 9 mm and a length of 20 cm. A healthy test subject was submitted to rectal manometry. The experimental data and analysis of linearity, hysteresis errors, temperature dependence and reproducibility are discussed. The sensor probe extends classical anorectal manometry, in particular with regard to the diagnosis of rectal motility disorders.

Automated CT image evaluation of the lung: a morphology-based concept.

UNLABELLED: Computed tomography (CT) provides the most reliable method to detect emphysema in vivo. Commonly used methods only calculate the area of low attenuation [pixel index (PI)], while a radiologist considers the bullous morphology of emphysema. The PI is a good, well-known measure of emphysema. But it is not able to detect emphysema in cases in which emphysema and fibrosis occur at the same time. This is because fibrosis leads to a low number of low-attenuation pixels, while emphysema leads to a high number of pixels. The PI takes the average of both and, consequently, may present a result within the normal range. METHOD: The main focus of this paper is to present a new algorithm of thoracic CT image evaluation based on pulmonary morphology of emphysema. The PI is extended, in that it is enabled to differentiate between small, medium, and large bullae (continuous low-attenuation areas). It is not a texture-based algorithm. The bullae are sorted by size into four size classes: class 1 being within the typical size of lung parenchyma; classes 2-4 presenting small, medium, and large bullae. It is calculated how much area the different classes take up of all low-attenuation pixels. The bullae index (BI) is derived from the percentage of areas covered, respectively, by small, medium, and large bullae. From the relation of the area of bullae belonging to class 4, to that of those belonging to class 2, a measure of the emphysema type (ET)is calculated. It classifies the lung by the type of emphysema in bullous emphysema or small-sized, diffuse emphysema, respectively. RESULTS: The BI is as reliable as the PI. In cases in which the PI indicates normal values while in fact emphysema is coexisting with fibrosis, the BI, nevertheless, detects the destruction caused by the emphysema. The BI combined with the ET reflects the visual assessment of the radiological expert. CONCLUSION: The BI is an objective and reliable index in order to quantify emphysematous destruction, hence, avoiding interobserver variance. This is particularly interesting for follow-up. The classification of the ET is a helpful and unique approach to achieving an exact diagnosis of emphysema.

New technical possibilities for simultaneous cystometry.

With the introduction of integrated semiconductor pressure pick-ups into the urodynamic methodology of analysis, the bladder and urethral manometry has been optimized, since the measuring transducer is positioned directly inside the lumen of the bladder. In this way, it is possible to eliminate the errors of conventional measuring methods with the liquid-filled or gas-filled catheter system, for example movements, vibrations, hydrostatic influences on the coupling medium by different vertical positions of the catheter or connecting tube, as well as cloggings due to haematuria or secretion of mucus. Owing to its dimensions and radiopaque properties, the IBW 78 tip manometer is suitable also for the pressure measurement in the upper urinary passages including the pyelon. The pressure signals obtained are further processed in a special plug-in unit for the biomonitor system, and thus they can be recorded on any multiple recorder.

[New technical possibilities for simultaneous cystometry]. / Neue technische Möglichkeiten zur simultanen Zystometrie.

With the introduction of integrated semiconductor pressure admitters into the urodynamic examination methodology an optimization of the manometry of the bladder and the urethra was carried out, since the changer of the measuring value in this case is directly situated in the lumen of the bladder. Thus it is achieved that the possibilities of errors which are connected with the conventional measuring method with the catheter system filled with fluid or gas, such as movements, concussions, hydrostatic influence of the coupling medium by different altitude level of the catheter and the connection tube, respectively, but also constipations in haematuria or excretions of the mucus may be excluded. The presented tip manometre IBW 74 due to its measures and radiopaque properties is also suited for the measurement of the pressure on the upper urinary tracts including the pyelon. Hereby the pressure signals gained are further elaborated through a special insertion for the biomonitor system and thus may be recorded on every multiple recorder.