Volume 54, Issue 2

Background : The efficacy of cardiac resynchronization therapy through biventricular pacing (BVP) has been demonstrated by numerous studies in patients suffering from congestive heart failure. In order to achieve a guideline for optimal treatment with BVP devices, an automated non-invasive strategy based on a computer model of the heart is presented. Materials and methods : The presented research investigates an off-line optimization algorithm regarding electrode positioning and timing delays. The efficacy of the algorithm is demonstrated in four patients suffering from left bundle branch block (LBBB) and myocardial infarction (MI). The computer model of the heart was used to simulate the LBBB in addition to several MI allocations according to the different left ventricular subdivisions introduced by the American Heart Association. Furthermore, simulations with reduced interventricular conduction velocity were performed in order to model interventricular excitation conduction delay. More than 800,000 simulations were carried out by adjusting a variety of 121 pairs of atrioventricular and interventricular delays and 36 different electrode positioning set-ups. Additionally, three different conduction velocities were examined. The optimization measures included the minimum root mean square error ( E RMS ) between physiological, pathological and therapeutic excitation, and also the difference of QRS-complex duration. Both of these measures were computed automatically. Results : Depending on the patient's pathology and conduction velocity, a reduction of E RMS between physiological and therapeutic excitation could be reached. For each patient and pathology, an optimal pacing electrode pair was determined. The results demonstrated the importance of an individual adjustment of BVP parameters to the patient's anatomy and pathology. Conclusion : This work proposes a novel non-invasive optimization algorithm to find the best electrode positioning sites and timing delays for BVP in patients with LBBB and MI. This algorithm can be used to plan an optimal therapy for an individual patient.

Analysis of the fetal ECG (fECG) allows physicians to detect changes in the well-being state of the fetus. But when assessing the fECG through the abdominal signals (ADS), its very low amplitude causes a problem, as the fECG representation in the ADS is buried in a mixture of other signals with stronger energy. Different methods have been proposed in the past to extract the transabdominal fECG for instantaneous fetal heart rate (fHR) computation; four representatives of them are selected for an accurate comparison of their performance in fECG extraction and in fHR estimation. A model for the ADS including all the possible disturbances is developed within this study to generate simulated data as they are required for the quantitative comparison of the algorithms. Their performances and limits considering both the enhancement of the fECG and the ability to preserve fECG morphology are analyzed using the simulated data. The results clearly show that linear methods for maternal ECG removal provide better results with respect to the extraction of the fECG morphology. The algorithms are then tested on real ADS data recorded during labor. Finally, the advantage of considering linear methods for ADS processing is discussed.

Gender-related differences in the pharmacology of drugs used in anaesthesiology have been reported by different authors. The aim of this study was to compare propofol dosages in a greater number of male and female patients who had received electroencephalogram (EEG) monitoring to maintain a defined depth of anaesthesia. Data from an EEG-controlled study were analysed with regard to gender differences in the consumption of the short-acting hypnotic propofol during maintenance of total intravenous anaesthesia and with regard to recovery times. The 656 patients (239 male, 417 female) were 15 to 97 years old, underwent different surgical procedures, and received propofol in combination with remifentanil, a short-acting opioid. During the steady-state of anaesthesia the EEG stage D 2 /E 0 , which corresponds to deep hypnosis, was the target level (EEG monitor: Narcotrend ® ). Propofol dosages were calculated as mg/kg body weight/h and as mg/kg lean body mass/h. Significantly higher propofol dosages were observed in female patients compared to male patients, especially with lean body mass as a reference parameter. The dosages were characterised by a high interindividual variability. The time from stop of propofol until extubation was significantly shorter in women than in men. The propofol dosage for maintenance of anaesthesia at the EEG level D 2 /E 0 decreased with increasing age. Zusammenfassung Über geschlechtsspezifische pharmakologische Unterschiede von Anästhetika ist von verschiedenen Autoren berichtet worden. Das Ziel dieser Studie war es, an einer größeren Zahl männlicher und weiblicher Patienten die Propofoldosierungen zu vergleichen, die zur Aufrechterhaltung einer anhand des EEG definierten Hypnosetiefe benötigt wurden. Daten aus einer EEG-kontrollierten Studie wurden hinsichtlich geschlechtsspezifischer Unterschiede im Verbrauch des kurzwirksamen Hypnotikums Propofol bei total-intravenöser Anästhesie und hinsichtlich der Aufwachzeiten analysiert. Die 656 Patienten (239 männlich, 417 weiblich) im Alter von 15 bis 97 Jahren unterzogen sich unterschiedlichen operativen Eingriffen in Anästhesie mit Propofol und dem kurzwirksamen Opioid Remifentanil. Die Steuerung der Narkosetiefe erfolgte mit Hilfe des EEG-Monitors Narcotrend, wobei zur Narkoseaufrechterhaltung das EEG-Stadium D 2 /E 0 angestrebt wurde, welches einem tiefen Schlafstadium entspricht. Propofoldosierungen wurden in mg/kg Körpergewicht/h sowie in mg/kg lean body mass/h errechnet. Im Vergleich zu den Männern war der Verbrauch an Propofol bei den Frauen signifikant höher, besonders wenn in Bezug auf lean body mass verglichen wurde. Dabei gab es große interindividuelle Unterschiede. Die Zeit vom Stopp der Infusion bis zur Extubation war bei den Frauen signifikant kürzer. Der Bedarf an Propofol zur Aufrechterhaltung der Narkose im Stadium D 2 /E 0 sank mit zunehmendem Alter.

Photoacoustic imaging combines the resolution of ultrasound imaging with the contrast of optical imaging, while maintaining a penetration depth up to a few centimeters. Inorganic gold nanorods can be employed as photoacoustic contrast agents. However, the toxicological properties of such nanoparticles are still under investigation. At the same time, there is an increasing need for clinically established photoacoustic contrast agents. In this paper, therefore, we investigate the photoacoustic properties of Ferucarbotran, which is a clinically established nanoscale contrast agent for magnetic resonance imaging. Gelatin phantoms containing cubes with different gelatin-Ferucarbotran mixture concentrations were prepared and irradiated by a Nd:YAG laser (1064 nm). First, the photoacoustic signals were acquired by a single element ultrasound transducer (7.5 MHz) and evaluated quantitatively. In a second setup, photoacoustic imaging of Ferucarbotran with a modified clinical scanner was demonstrated. The experiments showed that in order to achieve a 6 dB gain of received photoacoustic signal energy, compared to the sensitivity threshold of the used system, a Ferucarbotran concentration of 1.9 μmol Fe/ml is needed. The photoacoustic imaging was successful and showed a contrast-to-background ratio of 15.7 dB for a concentration of 11.63 μmol Fe/ml. However, for imaging in tissue the signal-to-noise ratio has to be increased. Zusammenfassung Die Photoakustik kombiniert die Auflösung der Ultraschallbildgebung mit dem Kontrast der optischen Bildgebung, wobei eine Eindringtiefe von bis zu einigen Zentimetern erhalten bleibt. Insbesondere können anorganische Gold-Nano-Rods auf Grund ihrer besonders starken optischen Absorption vorteilhaft als photoakustische Kontrastmittel eingesetzt werden. Die toxikologischen Eigenschaften dieser Partikel sind jedoch noch nicht eingehend geklärt. Gleichzeitig entsteht aber ein zunehmender Bedarf an klinisch zugelassenen photoakustischen Kontrastmitteln. Daher sollen ihm Rahmen dieser Arbeit die photoakustischen Eigenschaften von Ferucarbotran, einem klinisch eingesetzten Nanopartikel-Kontrastmittel für die Magnetresonanztomographie, evaluiert werden. Es wurden Gelatinephantome hergestellt, die einen Kubus mit verschiedenen Ferucarbotrankonzentrationen erhielten und mittels eines Nd:YAG-Lasers (1064 nm) bestrahlt wurden. Zunächst wurden photoakustische Signale durch einen Einzelelementultraschallwandler (7,5 MHz) aufgenommen und quantitativ ausgewertet. Anschließend wurde die photoakustische Bildgebung von Ferucarbotran mit einem modifizierten klinischen Ultraschallgerät demonstriert. Die quantitativen Experimente zeigen, dass, um einen Gewinn der Signalenergie aus dem Ferucarbotranblock von 6 dB gegenüber der Sensitivitätsgrenze des eingesetzten Systems zu erhalten, eine Konzentration von 1,9 μmol Fe/ml notwendig ist. Weiterhin wurden die Phantome erfolgreich photoakustisch abgebildet und ein Kontrast der Zielregion zum Hintergrund von 15,7 dB für eine Konzentration von 11,63 μmol Fe/ml erreicht. Für die Bildgebung im Gewebe muss das Signal-Rausch-Verhältnis des Systems jedoch noch weiter verbessert werden.

The aim of the present study was to investigate the biomechanical characteristics of orthodontic bracket systems made of metal, ceramics or plastics. Six different types of brackets were studied, including the Hanson Speed™- and Damon ® 2-Brackets, both of which are equipped with specialised closing mechanisms. In addition, two conventional metal brackets (Ultratrimm ® , Discovery ® ), the ceramics bracket Fascination ® 2 and the polycarbonate bracket Brillant ® were investigated. Stainless steel wires with the dimensions 0.40 mm×0.56 mm, 0.46 mm×0.56 mm, 0.46 mm×0.64 mm and 0.48 mm×0.64 mm were used with each bracket type simulating the clinical rotational movement of an upper central incisor in a biomechanical set-up. A buccal crown torque of 20° was applied and the correction of the malposition was simulated experimentally. Each bracket/wire combination was analysed five times. The following parameters were analysed: maximum torquing moment, torque angle correction, and moment/torque ratio. Combining a 0.48 mm×0.64 mm steel wire with the ceramics brackets (Fascination ® 2) delivered the highest torquing moment (35 Nmm). The best torque correction was achieved with plastic brackets (17°). The lowest moments were approximately 5.2 Nmm (Damon ® 2, 0.40 mm×0.56 mm steel wire), being in the range of the recommended minimum torquing moment (5 Nmm). Discovery ® brackets delivered similar low moments. Overall, only minor differences exist between the various bracket systems with regard to their efficiency in torque correction. Clinically, the wire/slot play seems to be more important than differences in the bracket designs.

Background: Plasma treatment leads to a significant change of surface free energy of medical implant materials. These changes strongly influence protein and cell adhesion on the material surface. The aim of the study was to quantify the plasma-induced surface changes and to analyse whether the change of treatment parameters, such as pressure, gas mixture, energy and treatment time, influences the surface free energy of the implant materials. To improve the biocompatibility of the surfaces, polyamino acid coating experiments were performed. Materials and methods: Three different metal implant materials (X2CrNiMo18-15-3, Ti6Al4V, Ti6Al7Nb) were treated with a double-inductively coupled low-pressure plasma. The influence of treatment parameter variation on the surface free energy was evaluated by drop shape analysis. The plasma treated and non-treated materials were incubated in collagen I solution. Afterwards, the coatings were analysed by electron microscopy in terms of structure and adhesion. Results: Drop shape analysis revealed that plasma treatment leads to a significant increase of surface free energy in all groups. Long plasma treatment times and low treatment pressures lead to a significant (p<0.05) extension of the detectable surface free energy increase. Coating experiments showed that only on plasma-treated samples solid and adherent collagen layers could be achieved.