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A computer-assisted interactive method for M-scan analysis is presented. The digital M-scan, which is taken from the posterior wall of the human eye - in vivo - , is a sequence of digitised, broadband r.f.-time amplitude echograms (center frequency: 15 MHz). The effect of pulsation in the normal posterior wall of the eye and the dynamic changes and tissue movements after stress conditions can be pointed out and estimated quantitatively. A detected set of dynamic features can be used for an exact determination of the layers of the posterior ocular wall. For the indication of the dependence between changes of the thickness of the layers and the heart rate, the finger pulse is digitised and stored synchronously to the echograms. Good correlation will be expected for the movements in the choroid of the eye and the heart rate. The registration of the dynamics is performed in the color-coded M-scan by an adapted image processing software. Results of the M-scan analysis are presented as examples of the normal posterior wall.

An ultrasonic method for periodontal diagnosis has been developed by the authors. A fundamental part of this work is the evaluation of the acoustical properties of the hard tissues: enamel, dentine and alveolar bone. Using an adapted measuring device, in combination with a computer-controlled signal acquisition and analysing system, acoustical parameters (velocity, impedance and frequency-dependent attenuation) are determined. The knowledge of these parameters is a prerequisite for a correct interpretation of A-mode and B-mode images, representing parts of the oral/facial aspect of a periodontium.

For magnetic stimulation the desired electromagnetic field is produced by a magnetic coil to affect biological tissue and thereby to stimulate it for neurological diagnosis. The coil geometry determines the strength and the duration of the induced electric field in the volume of interest for a given stimulator: The aim of our work is to establish a relationship between the coil geometry and the strength as well as duration of the induced electric field. The calculated results show that there exists an optimal coil geometry for stimulating a given volume of the biological tissues. Our numerical calculation is restricted to an excitable tissue 15 mm below the lower plane of the coil.

In a detailed study mechanical properties of tendons, muscles, nerves, blood-vessels and skin of just slaughtered pigs have been investigated in nearly stationary stress tests. Tensile tests have produced tensile strength, ultimate stress and their appropriate strains, Young's modulus and the work up to fatigue of samples. In hysteresis tests the deformation work has been determined as a function of numbers of stress cycles. The hysteresis decrease with the number of stress cycles and approaches asymptotically to cero. By preconditioning of tendons, nerves and blood-vessels to steady state significant differences of strain at tensile strength and of Young's modulus have been established. Moreover for nerves the tests have revealed significant deviations of tensile strength. Bruise tests have been carried out with muscle tissue. For the described setup the limit force can be specified, at which pathological changes appear. Subsequently conducted histological investigations have demonstrated this. In dynamical bruise tests there appeared no pathological changes in muscle tissue in spite of higher transmitted energy.

Stable temperature conditions are demanded for biochemical measurements. A system is presented for controlling the temperature of a solution in a measuring cell within an accuracy of ±0.02 K at any room temperature for longer than half an hour. An ultrasound transmitter rapidly warms the solution in a 2 ml cell to the desired temperature (0.5 K/s). Simultaneously, the environment of the cell is kept at the same temperature by circulation of a small volume of water. Its temperature is precisely regulated by a Peltier Thermal Supply controlled by a State Controller. The ultrasound application, the temperature control of the environment of the cell and the data acquisition for the measuring procedures are performed by a MS DOS Personal Computer. This system has been applied to photometric measurements of reaction kinetics to determine the enzymatic activity and the activation energy. The reproducibility achieved has been ±1% and ±1 kJ/mol, respectively.

A wide-band high-speed data acquisition system for electrical impedance tomography (EIT) is described. 32 active electrodes are used in the system, half of them as receive electrodes and the other half as drive electrodes. A buffer is mounted on the back of each receive electrode and a current source on each drive electrode. A multielectrode system with active electrodes was built to make it convenient to attach all the electrodes on the human thorax. The system is suitable for both dynamic imaging and multifrequency electrical impedance tomography (MFEIT). Its operating frequency can be chosen between 25 kHz and 400 kHz. Current is injected sequentially into 16 adjacent current electrode pairs and the 16 voltages between adjacent receive electrodes are measured for each current injection. ECG is collected to determine the relationship between the reconstructed images and cardiac activity. The collection of one frame of data is completed within 25 ms. The system has been successfully used for imaging the variation of conductivity distribution of the human thorax. The beat-by-beat cardiac-related change of conductivity distribution has been imaged by our system. The quasi-periodic variation of the impedance distribution can be seen from the image sequence with breath-holding.

In a detailed study mechanical properties of tendons, muscles, nerves, blood-vessels and skin of just slaughtered pigs have been investigated in nearly stationary stress tests. Tensile tests have produced tensile strength, ultimate stress and their appropriate strains, Young's modulus and the work up to fatigue of samples. In hysteresis tests the deformation work has been determined as a function of numbers of stress cycles. The hysteresis decrease with the number of stress cycles and approaches asymptotically to cero. By preconditioning of tendons, nerves and blood-vessels to steady state significant differences of strain at tensile strength and of Young's modulus have been established. Moreover for nerves the tests have revealed significant deviations of tensile strength. Bruise tests have been carried out with muscle tissue. For the described setup the limit force can be specified, at which pathological changes appear. Subsequently conducted histological investigations have demonstrated this. In dynamical bruise tests there appeared no pathological changes in muscle tissue in spite of higher transmitted energy.

A versatile simulation software for modelling a complete US B-mode system is presented. The great flexibility of the simulation system makes it possible to determine the influence of all system parameters to the image quality of a US B-mode system.

An ultrasound tomography system has been developed to measure cross-sectional images using both transmission and conventional reflection mode. With the existing technology the combination of ultrasound techniques is useful to improve the quality of image and their diagnostic value. The additional tissue-specific informations of quantitative transmission images increase the diagnostic accuracy over that obtained by puis echo imaging only.

Comprehensive software and hardware have been developed for the processing of biosignals. Such automatic signal processing, however not only has advantages, but also drawbacks. The question as to the reliability of the evaluation algorithm arises when the signal is modified, in the presence of interindividual differences, and in particular when noise is superimposed. This is of great interest for long-term recording when the original signal can no longer be inspected visually. The aim of our work was to display the signals on the screen of a monitor simultaneously with lines marking the points (start, end, extreme value, etc.) processed by the specific signal processing algorithm. The program package permits the on-line recording and monitoring of signals, the parallel processing and marking of detected events on the monitor, as well as storage of the parameters extracted. It is a very effective tool for developing, improving and monitoring of algorithms and their efficiency for signal processing.

Die objektive Beurteilung von medizinischen Ultraschall B-Bildaufnahmen stellt aufgrund der oftmals unzureichenden raumlichen Auflosung und des schlechten Signal/Rauschverhaltnisses ein schwieriges Problem dar. Eine Verbesserung dieses Verhaltnisses bei gleichbleibender axialer Auflosung ermoglicht das nach dem Optimalfilterprinzip arbeitende Verfahren der Pulskompression /1/.