Technology and Health Care - Volume 4, issue 1

Authors: Botnar, R. | Scheidegger, M.B. | Boesiger, P.

Article Type: Research Article

Abstract: The quantitative assessment of velocity fields can help to get a better understanding of complicated flow patterns which are considered to play an important role in atherosclerotic plaque formation. Magnetic resonance imaging offers the possibility of non-invasive visualization and quantification of blood flow in many larger human arteries and veins. However, the assessment of complex blood flow patterns with conventional gradient echo flow sequences sutler from severe image artifacts. In order to overcome these problems, a partial echo signal acquisition technique which strongly reduces such artifacts may be applied. Using this technique, three dimensional velocity fields were measured in a …bifurcation model, in the human carotid bifurcation and in the human aorta, right downstream of the aortic valve. Show more

Keywords: Complex blood flow, magnetic resonance imaging, atherosclerosis

DOI: 10.3233/THC-1996-4111

Citation: Technology and Health Care, vol. 4, no. 1, pp. 97-112, 1996

Authors: Müller, R. | Koller, B. | Hildebrand, T. | Laib, A. | Gianolini, S. | Rüegsegger, P.

Article Type: Research Article

Abstract: Micro-computed tomography (μCT) is an emerging technique for the non-destructive assessment and analysis of the three-dimensional cancellous bone architecture. However, the procedures and applications used to quantify bone structures are not yet standardized. The aim of this study was to provide more insight in the resolution-dependency of microstructural properties of three-dimensional trabecular bone. Ten iliac crest bone biopsies were measured using a newly devised μCT system providing a nominal isotropic resolution of 14 μm. To study the resolution dependency, the measured data were reconstructed on reduced image arrays with reduction factors ranging from 2 to 20. To assess the structural …properties, morphometric parameters were computed based on a truly three-dimensional approach. The results showed a strong resolution dependency of the structural properties and that, if very precise results are needed, only the highest resolution will predict the correct values. Nevertheless, since the properties either decrease or increase monotonously up to a nominal resolution of about 175 μm, the values appear to be restorable using a suitable calibration procedure. Show more

Keywords: Micro-computed tomography (μCT), trabecular bone architecture, quantitative bone morphology, 3D structural analysis, image resolution

DOI: 10.3233/THC-1996-4112

Citation: Technology and Health Care, vol. 4, no. 1, pp. 113-119, 1996

Authors: Di Rienzo, M. | Castiglioni, P. | Parati, G. | Mancia, G. | Pedotti, A.

Article Type: Research Article

Abstract: This paper focuses on a number of methods for the analysis of the relationship between the arterial baroreflex and different components of blood pressure and heart rate variability. Broad-band spectral analysis techniques have allowed us to obtain experimental evidence that the arterial baroreflex exerts its influence not only on fast but also on slow components of blood pressure and heart rate, i.e., on components with periods longer than 60 sec. Focusing on faster changes in blood pressure and heart rate, both time domain and frequency domain techniques have been developed to track the sensitivity of baroreflex heart rate modulation over …time, either in laboratory or in daily life conditions. These approaches have considerably broadened our understanding of the role of baroreflex modulation of the heart and peripheral circulation in a number of pathological and physiological conditions. Show more

DOI: 10.3233/THC-1996-4113

Citation: Technology and Health Care, vol. 4, no. 1, pp. 121-128, 1996