PURPOSE: There is controversy about relevant EEG signal changes indicating adequate or inadequate anaesthesia. Differences of drug-induced and nociceptive mediated signal changes have not been studied in detail. The present study investigates whether signal changes during decreases of depth of anaesthesia due to surgical stimulation depend on different isoflurane concentrations during sufentanil anaesthesia. METHODS: Following IRB approval and written informed consent 28 patients (ASA: I; age 43 +/- 11 y) scheduled for elective abdominal surgery were included in the study. Anaesthesia: propofol (2.0 mg/kg) and sufentanil (1.0 micrograms/kg). Following endotracheal intubation (vecuronium 0.1 mg/kg) patients were normoventilated (P(ET)CO2: 36-38 mmHg). Randomly assigned to steady-state anaesthesia (group 1: P(ET)Isoflurane 0.2%, (14n); group 2: P(ET)Isoflurane 0.6%, (14n) during the start of surgery. Monitoring: heart rate (HF), mean arterial blood pressure (MAP), P(ET)CO2, arterial oxygen saturation and rectal temperature. EEG (16 channels referenced to Cz; CATEEM, Medisyst, Linden) recorded 5 min before until 10 min after the start of surgery. EEG-analysis (FFT: 4s, 256/s, 0.45-35.0 Hz): topographical distribution of power spectral densities (delta, theta, alpha 1, and alpha 2). Artifact control: ECG and EOG. RESULTS: Surgical stimulation resulted in increases of MAP in both groups (p < 0.05 vs BL), whereas HR was only slightly affected in group 2 when compared with BL. Other variables except of EEG data did not change over time. In group 1 (0.2% isoflurane) surgical stimulation resulted in decreases of delta over the whole cortex (F2, C3, P3, O1) and in marked increases of alpha predominantly at central leads (C3)(p < 0.05 vs BL). In group 2 (0.6% isoflurane) nociceptive stimulation was associated with decreases of faster waves (alpha: F3)(p < 0.05 vs BL) and increases in delta at fronto-central areas (F3, C3)(p < 0.05 vs BL). CONCLUSIONS: EEG recordings are useful in assessing pharmacodynamic drug effects. In contrast, intraoperative EEG recordings have a low correlation to clinical signs of changes in the anaesthetic state. Previous studies demonstrate paradoxical EEG-arousal reactions during isoflurane anaesthesia. The present data suggest that classical or even paradoxical EEG arousal due to nociceptive stimulation may depend on the isoflurane concentration. It seems reasonable that the ascending reticular formation is functionally blocked by isoflurane in a dose-dependent manner.
U. Eck, G. Vossius, and R. Rupp. [The contribution of EMG for monitoring controlled electrostimulation in paralysis. 2.) Applications of EMG]. In Biomedizinische Technik. Biomedical Engineering, vol. 43 Suppl, pp. 118-120, 1998
In the last few years, radioactive stents has been proved to inhibit neointima formation. This paper describes the actual status of producing such radioactive stents. After a short discussion of the different radioisotopes suitable for radioactive stents, potential production methods are discussed. The ion beam implantation of P-32 applied at the Karlsruhe Research Centre shall be described in more detail.
A prerequisite for the further improvement in the quality of warming therapy is an accurate knowledge of the interactions between the microclimate in warming therapy devices and the thermal balance of the infant. For generating this knowledge, thermal manikins can be helpful. Suitable models capable of also simulating evaporative heat loss in preterm infants have, however, not been available to date. A thermal manikin representing an infant weighing 530 g and capable of simulating convective, radiative and also evaporative heat loss has now been developed. It comprises an outer shell made of porous, anatomically shaped clay, and is divided into six compartments each of which can be heated individually. Water-filled Gore-Tex bags located immediately beneath the shell are provided to simulate evaporation. In a clinical study, temperature profiles of 8 very small preterm infants were measured thermographically. Measurements in the manikin showed that highly comparable temperature profiles with only minor differences could be obtained. Total heat and water losses by the manikin were in good agreement with clinical values. Using the model described here it is possible to simulate the heat exchange of premature infants under extreme and accurately reproducible environmental conditions. This manikin may thus serve as a tool for comparative studies, for the development of warming therapy equipment, or for training purposes.
R. T. Frankenberger, O. Bussmann, W. Nahm, E. Konecny, and L. Gortner. Messung seitlicher Haupttemperaturprofile von Frühgeborenen in Inkubatoren mittels Thermograhpie - Measuring lateral skin temperature profile of premature infants in incubators with thermography. In Biomedizinische Technik. Biomedical Engineering, vol. 43(6) , pp. 174-178, 1998
Thermography enables the measurement of patients skin temperature profiles without stress caused by direct contact of probes to the skin. In previous incubator studies, frontal recordings were made through a hole in the top wall of the incubator hood. Using this method it is not possible to record the lateral temperature gradient from the back to the abdomen of the infant (in supine position), which is due to very limited heat loss near the incubator mattress. In this study temperature recordings were made from a lateral position. For this purpose a new front door of the incubator (Draeger 8000) was designed, which replaced the standard front door during measurements. In a clinical study thermography was compared to temperature measurements by standard thermistors. The mean difference between thermography and thermistors was 0.16 degree C. These results verify the use of thermography for measuring skin temperature of preterm infants in incubators.
The present paper examined the question as to the extent to which the taking of gas samples for the purpose of measuring the breath alcohol concentration (BAC) in the expired air of patients on artificial respiration is influenced by temperature and humidity. For this purpose a lung model standardized at different alcohol concentrations was used, in which the temperature (T: 25, 30 and 35 degrees C) and the relative humidity (RH: 50, 75 and 95%) were varied.
UNLABELLED: When looking for the possible cause of distortions in values measured for the determination of breath ethanol concentration (BEC) in artificially respirated patients, consideration must be given to the humidity and temperature of the gas examined. In the present study, the effects of humidified and warmed and of dry and cold air on the accuracy of a newly developed BEC measuring device, as compared to a reference model and to a conventional system, were examined in a lung model. METHODS: A temperature-regulated pediatric incubator was used containing a 10 I gas reservoir and a breath humidifier with temperature regulated water bath. This setup provided constant temperature and humidity in the gas examined during measurement period. In the 'expiration' the air was directed from the breath humidifier through a measuring unit via a 'mouthpiece' into the reference system (Alcotest 7110, Dräger Inc., Lübeck) and then out. The measuring unit consisted of sensors for the temperature and relative humidity, and of a connector for the three sample extraction systems (PES). PES I was the conventional system with a 100-cm gas-sample pipe (Alcomed 3010), PES II the newly developed system (AlcoMed 3011, both from Envitec, Wismar) with a 10-cm gas-sample pipe, and PES III with a 20-cm heated gas-sample pipe. During 'inspiration' 2 l of air was fed into the system to rinse the measuring unit and to fill the reservoir. 61 measurements were performed with dry and cold air, and 71 with humidified and warmed air, in the course of which the ethanol concentration was increased from 0 to 1.5/1000. Data were evaluated using regression analysis and the Bland & Altman method. RESULTS AND CONCLUSIONS: The constancy of the values set for temperature, relative humidity and absolute humidity in the lung model was given for all measurements. In the dry and cold air, the results from all three test systems coincided almost perfectly with the reference values. The measured BEC in the humidified and warmed air using sample-extraction systems II and III corresponded to a high degree with the reference, while in the case of PES I, only a moderate linear correlation was achieved. The temperature and humidity of the expired gas during artificial respiration influence the gas samples extracted for the purposes of BEC measurement. Newly developed sample-extraction systems II and III coincide with the reference system, even under respiration-simulated gas conditions.
F. Kreuder, B. Schreiber, C. Kausch, and O. Dössel. A structure-based method for on-line matching of portal images for an optimal patient set-up in radiotherapy. In Philips Journal of Research, vol. 51(2) , pp. 317-337, 1998
In radiotherapy, portal images are used to ensure a correct patient position during every radiation session. A reliable on-line verification is of clinical interest to interrupt the radiation in time in case the patient is not at the right position. A great problem for successful image registration is the poor image quality of portal images. They are corrupted by noise and of very low contrast. A method directly based on the grey levels is not sufficient. Therefore a structure-based method was developed which is almost insensitive to distrubances (air bubbles, noise, slowly varying grey levels). In most cases the selection of a region of interest (ROI) can be omitted. Besides the automatical segmentation of the radiation field, only the structures relevant for matching the anatomy are enhanced by using a bandpass filter. It is possible to detect the maximum correlation between different image modalities reliably (simulator image, digitally reconstructed radiograph, portal image). By using Fast Fourier Transformation (FFT), the calculation time is smaller than five seconds, which enables a clinical on-line verification. We have matched 1139 pairs of images of different modalities and various regions of the body (pelvis, nasopharyngeal space, head, lung). The success rate is greater than 95%.
S. Krey, B. David, R. Eckart, and O. Dössel. Low noise operation of integrated YBa2Cu3O7 magnetometers in static magnetic fields. In Applied Physics Letters, vol. 72(24) , pp. 3205-3207, 1998
The noise of two integrated YBa2Cu3O7-SrTiO3-YBa2Cu3O7 multilayer magnetometers in static magnetic fields up to 110 µT is investigated: An inductively coupled magnetometer with integrated flux transformer and a multiloop magnetometer. In both samples, only a moderate increase of the low frequency flux noise is found in high fields, due to the high epitaxial quality of the involved multilayer films. So for moderately shielded or unshielded applications in the earth's magnetic field, high-quality integrated YBa2Cu3O7 magnetometers can be operated with low excess noise.
R. Rupp, G. Vossius, and H. J. Gerner. [Contribution of EMG to monitoring controlled electrostimulation in paralysis: 1) Realization of a modular EMG recording hardware]. In Biomedizinische Technik. Biomedical Engineering, vol. 43 Suppl, pp. 242-244, 1998
F. B. Sachse, M. Wolf, C. D. Werner, and K. Meyer-Waarden. Extension of anatomical models of the human body: three dimensional interpolation of muscle fiber orientation based on restrictions. In Journal of Computing and Information Technology, vol. 6(1) , pp. 95-101, 1998
This paper is the extension of a detailed anatomical model (Sachse et al., 1996a) (Sachse et al., 1996b) with the three-dimensional orientation of skeletal muscle fibres (Figure 1). The orientation is interpolated basing on two sets with restrictions of different types. The first set consists of points for which the orientation is known. The second set consists of points with an assigned normal of orientation. These sets are created by detection with manual or automatic methods using techniques of digital image processing. The interpolation works iteratively employing the averaging orientations in the 6-neighbourhood. The average of neighbouring orientations is calculated by determination of their principal axis.
Book Chapters (3)
J. Abke, W. Nahm, and E. Konecny. Implementierung einer Bispektralanalyse in LabVIEW zur Beurteilung von Narkosetiefe über das EEG. In Virtuelle Instrumente in der Praxis - Meßtechnik, R. Jamal, H. Jaschinski (eds), VDE-Verlag, pp. 256-264, 1998
M. Daumer, W. Nahm, M. Scholz, and F. Danneger. Online Monitoring mit virtuellen Instrumenten. In Virtuelle Instrumente in der Praxis - Meßtechnik, R. Jamal, H. Jaschinski (eds), VDE-Verlag, pp. 265-270, 1998
I. H. d. Boer, F. B. Sachse, and O. Dössel. Entwicklung eines 4-Kamera-Systems zur Lokalisation einer Elektrodenanordnung auf dem Thorax. In Biomedizinische Technik, vol. 43-1, pp. 56-57, 1998
N. H. Busch, F. B. Sachse, C. D. Werner, and O. Dössel. Segmentation klinischer vierdimensionaler magnetresonanztomographischer Aufnahmen mittels Aktiver Kontur Modelle und haptischer Interaktion. In Biomedizinische Technik, vol. 43-1, pp. 526-529, 1998
O. Bussmann, W. Nahm, and E. Konecny. Modell zur Simulation der Wärmeabgabe und Thermoregulation Frühgeborener - A Model for simulating heat transfer and thermoregulation of premature infants. In Biomedizinische Technik/Biomedical Engineering, vol. 43(s1) , pp. 300-301, 1998
M. Daumer, W. Nahm, M. Scholz, F. Dannegger, G. Morfill, E. Kochs, and A. Neiss. Konzept für eine Internet-basierte Datenbank zur Unterstützung von Projekten auf dem Gebiet der Biosignalanalys - Concept for an internet-based databank for supporting projects in the area of biosignal analysis. In Biomedizinische Technik. Biomedical Engineering, vol. 43 s3, pp. 23-26, 1998
O. Dössel, F. R. Schneider, and M. Müller. Optimization of electrode positions for multichannel electrocardiography with respect to electrical imaging of the heart. In Engineering in Medicine and Biology Society, 1998. Proceedings of the 20th Annual International Conference of the IEEE, vol. 1, pp. 71-74, 1998
A procedure to find the optimal electrode positions for multichannel electrocardiography is presented. The criterion is the ability to reconstruct images of the electrical activity of the heart. Singular value decomposition of the lead field matrix is the chosen approach. The finite element method is used for numerical field calculation to determine the lead field matrix. Estimates on the expected measurement error play an important role in the optimization procedure. The optimal arrangement of electrodes is compared with other electrode positions reported in the literature using different optimization criteria. Body surface potential maps (BSPM) are measured on a healthy volunteer using the optimized electrode arrangement and preliminary epicardial potential patterns are reconstructed
M. Kelling, Z. Hussein, W. Nahm, and E. Konecny. Experimenteller Aufbau zur nicht-dispersiven Messung des Isotopenverhältnisses 13C/12C in Gasen - Experimental development of non-dispersive measurement of 13C/12C isotope relations in gases. In Biomedizinische Technik. Biomedical Engineering, vol. 43 Suppl, pp. 280-1, 1998
P. Knoop, C. Hornberger, W. Nahm, and E. Konecny. Entwicklung eines optischen Kalibrators für kommerzielle Pulsoximeter: Erste Erfolge - Development of an optical calibrator for commercial pulse oximeters: initial successes. In Biomedizinische Technik. Biomedical Engineering, vol. 43 s1, pp. 128-129, 1998
Wir präsentieren einen Algorithmus zur Erstellung von Finite Elemente Modellen des menschlichen Körpers. Ein von uns entwickelter Netzgenerator zerlegt ein durch Voxeldaten vorgegebenes Volumen in ein unstrukturiertes Tetraedergitter, welches das Delaunay Kriterium erfüllt. Sind die Ausgangsdaten gewebeklassifiziert, so erfolgt die Modellerzeugung basierend auf einem Teile und Herrsche Algorithmus automatisch, bei unklassifizierten Voxeldaten können unterstützend Grenzflächen mit Aktiven Konturen oder Marching Cubes erzeugt werden.
W. Nahm, G. Stockmanns, M. Daumer, J. Abke, and E. Konecny. Automatische EEG-Datenvorverarbeitung in einer Multicenterstudie - Automatic EEG data processing in a multicenter study. In Biomedizinische Technik/Biomedical Engineering, vol. 43(s1) , pp. 146-147, 1998
K. Ottosdottir, T. Helgason, and O. Dössel. Ein System zur Erfassung und Darstellung geometrischer Größen aus Videoaufnahmen zur Bewegungsanalyse des menschlichen Körpers. In Biomedizinische Technik, vol. 43-1, pp. 522-523, 1998
F. B. Sachse, C. D. Werner, K. Meyer-Waarden, and O. Dössel. Applications of the Visible Man Dataset in Electrocardiology: Calculation and Visualization of Body Surface Potential Maps of a Complete Heart Cycle. In Proc. Second Users Conference of the National Library of Medicines Visible Human Project, pp. 47-48, 1998
This study deals with the forward problem in electrocardiography, which consists of computing the electrical potential distribution in the human body due to cardiac sources. Thereby, an important task is the selection of appropriate models, because their properties determine the quality and costs of the solution of the forward problem. Subject of this study is an examination, which regions of the body should be included in impedance models. Therefore, different impedance models, varying in position and size, are examined. They were derived from a realistically shaped, highly detailed anatomical model. The model originates from tomographies of the Visible Man dataset, National Library of Medicine, Bethesda, Maryland (USA), using techniques of digital image processing. The examination is carried out by analysis and comparison of computed body surface potential maps, which are numerically calculated based on a set of different models using the finite difference method
F. R. Schneider, O. Dössel, and M. Müller. Filtering Characteristics of the Human Body and Reconstruction Limits in the Inverse Problem of Electrocardiography. In Proc. Computers in Cardiology, vol. 25, pp. 689-692, 1998
F. Schneider, O. Dössel, and M. Müller. Filtering characteristics of the human body and reconstruction limits in the inverse problem of electrocardiography. In Proceedings of Computers in Cardiology, pp. 689-692, 1998
The inverse problem of electrocardiography, consisting of the reconstruction of bioelectrical sources on the heart from measured body surface potentials, is an ill-posed problem. The human body with its tissue inbetween the heart and the body surface behaves like a filter, that damps or even eliminates higher spatial frequencies of source distributions on the heart. The source distributions leading to body surface potentials which are smaller than noise cannot be measured and belong to the nullspace. The extent of the nullspace for a given model of the human body and for a given measurement accuracy depends strongly on the chosen electrode positions and the source locations. Without regarding any modelling error, this study investigates the limits of reconstructable source patterns for two different finite element models. To determine the reconstruction limits for these datasets, the best electrode positions and the accurate number and locations of bioelectrical sources on the heart must be found
C. D. Werner, F. B. Sachse, and O. Dössel. Vergleichende Betrachtung von isotropen und anisotropen Modellen der Erregungsausbreitung im Herzen. In Biomedizinische Technik, vol. 43, pp. 69-70, 1998
C. D. Werner, F. B. Sachse, and O. Dössel. Electrical excitation of the human heart: A comparison of electrical source distribution in models of different spatial resolution. In Proc. Computers in Cardiology, vol. 25, pp. 309-312, 1998
Subject of this study is the simulation of the electrical excitation propagation based on anatomical and physiological models of the human heart. An anatomical model of high spatial resolution was created applying advanced strategies of 3D digital image processing to the Visible Human data set provided by the National Library of Medicine, Bethesda, Maryland (USA). It comprises 42 classes of tissue including the cardiac conduction system. In addition, the fibre orientation of the cardiac and skeletal muscle was determined end assigned to each voxel of the model. Source distributions were calculated based on a 3D bidomain model applying a cellular automaton to these models to simulate the excitation process. The anisotropic behaviour of the cardiac muscle with regard to electrical conductivity and propagation velocity was taken into account as well as physiological properties of the cardiac tissue. Source distributions of differently scaled models were compared
Die in dieser Arbeit vorgestellte Strategie der Segmentation und Klassifikation drei- und Vierdimensionaler MR-Datensätze ermöglicht die Erstellung anatomischer Modelle des menschlichen Körpers. Zur Segmentation dieser Datensätze kommen unterschiedliche Verfahren zum Einsatz. Schwerpunkte bilden dabei das Region Growing und die Aktiven Konturen. Bei beiden Segmentationsverfahren werden zur Filterung der Datensätze unterschiedliche Filter (u. a. Gauß-, Sobelfilter, nichtlineare adaptive Diffusionsfilter, morphologische Filter) angewendet. Das aktive Konturen-Verfahren wird weiterhin durch die Wahl geeigneter Potentialfunktionen unterstützt.
C. Werner, F. Sachse, and O. Dössel. Applications of the visible human male dataset in electrocardiology: simulation of the electrical excitation propagation. In Proceedings of 2nd User Conference of the National Liberary of Medicines Visible Human Project, pp. 69-70, 1998
Due to its high spatial resolution the Visible Man dataset provides a good possibility to simulate certain aspects of human physiology based on detailed, macroscopic models of the human anatomy. This study deals with the simulation of the electrical excitation propagation in the human heart. Along with applications in education, diagnosis and therapy, this simulation is used in manifold fields of research, such as solving the forward problem of electrocardiography with a realistic boundary condition or validating solutions of the inverse problem of electrocardiography. The simulation is based on an anatomical and physiologocal model of the heart of the Visible Man. The anatomical model was created exploring the data provided with the thin-section photos of the Visible Man dataset. The simulation of the electrical excitation propagation was performed by a cellular automaton which combines the anatomical model with physiological parameters of the electrical excitation propagation. It allowed to calculated the electrical source distribution in the heart numerically which was used to solve the forward problem of electrocardiology which is the calculation of body surface potential maps from a given source distribution.
M. Müller. Berechnung dreidimensionaler Strömungsfelder der transthorakalen Defibrillation im menschlichen Körper mit der Finite-Elemente-Methode. Institut für Biomedizinische Technik. Dissertation. 1998
M. Müller. Berechnung dreidimensionaler Strömungsfelder der transthorakalen Defibrillation im menschlichen Körper mit der Finite-Elemente-Methode. Universität Karlsruhe. Dissertation. 1998
F. B. Sachse. Modelle des menschlichen Körpers zur Berechnung von physikalischen Feldern. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Dissertation. 1998
A. Steingötter. Kompression dreidimensionaler medizinischer Bilddaten. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Dissertation. 1998
Student Theses (4)
O. Abdallah. Bestimmung von Body Surface Potential Maps durch Simulation der Erregungsausbreitung im Herzen unter Berücksichtigung anisotroper Gewebeeigenschaften. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Diplomarbeit. 1998
N. H. Busch. Segmentation klinischer vierdimensionaler magnetresonanztomographischer Aufnahmen mittels Aktiver Kontur Modelle und haptischer Interaktion. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Diplomarbeit. 1998
A. Herrmann. Aufbau eines Multikanalmeßsystems und Validierung von Verfahren zur Rekonstruktion bioelektrischer Quellen im menschlichen Körper. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Diplomarbeit. 1998
S. Jarayseh. Entwicklung und Implementierung eines Matchingverfahrens für die ultraschallbasierte Registrierung in der computerunterstützen Hüftgelenksendoprothetik. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Diplomarbeit. 1998