IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Apr 2005
Comparative StudyPulsatile cerebrospinal fluid dynamics in the human brain.
Disturbances of the cerebrospinal fluid (CSF) flow in the brain can lead to hydrocephalus, a condition affecting thousands of people annually in the US. Considerable controversy exists about fluid and pressure dynamics, and about how the brain responds to changes in flow patterns and compression in hydrocephalus. This paper presents a new model based on the first principles of fluid mechanics. ⋯ The model also quantifies the pulsatile CSF motion including flow reversal in the aqueduct as well as the changes in ICPs due to brain tissue compression. It does not require the existence of large transmural pressure differences as the force for ventricular expansion. Finally, the new model gives an explanation of communicating hydrocephalus and the phenomenon of asymmetric hydrocephalus.
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IEEE Trans Biomed Eng · Apr 2005
A system-on-chip digital pH meter for use in a wireless diagnostic capsule.
This paper describes the design and implementation of a system-on-chip digital pH meter, for use in a wireless capsule application. The system is organized around an 8-bit microcontroller, designed to be functionally identical to the Motorola 6805. ⋯ The chip is designed in a modular fashion to facilitate verification and component re-use. The single-chip pH meter can be directly connected to a personal computer, and gives a response of 37 bits/pH, within an operating range of 7 pH units.
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IEEE Trans Biomed Eng · Apr 2005
Comparative Study Clinical TrialQuantifying errors in spectral estimates of HRV due to beat replacement and resampling.
Spectral estimates of heart rate variability (HRV) often involve the use of techniques such as the fast Fourier transform (FFT), which require an evenly sampled time series. HRV is calculated from the variations in the beat-to-beat (RR) interval timing of the cardiac cycle which are inherently irregularly spaced in time. In order to produce an evenly sampled time series prior to FFT-based spectral estimation, linear or cubic spline resampling is usually employed. ⋯ Resampling and phantom beat replacement is shown to decrease the accuracy of PSD estimation, even at low levels of ectopy or artefact. A linear relationship between the frequency of ectopy/artefact and the error (mean and variance) of the PSD estimate is demonstrated. Comparisons of PSD estimation techniques performed on real RR interval data during minimally active segments (sleep) demonstrate that the LS periodogram provides a less noisy spectral estimate of HRV.
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IEEE Trans Biomed Eng · Apr 2005
Comparative StudyComparing generalized and phase synchronization in cardiovascular and cardiorespiratory signals.
We made use of multivariate nonlinear analysis methods to study the interdependence between the cardiac interval variability and both the respiratory activity and the systolic pressure in rats. The study was carried out in basal conditions and after the application of different drugs affecting the cardiovascular system. ⋯ The inhibition of the NO and the parasympathetic blockade changed the cardiovascular coordination, with the latter one also modifying the interdependence between the cardiac interval and the respiratory signal. This suggests that the nonlinear approach might be very helpful to explore the interaction between subsystems of the cardiovascular control system.
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IEEE Trans Biomed Eng · Apr 2005
Comparative StudyElastic registration of biological images using vector-spline regularization.
We present an elastic registration algorithm for the alignment of biological images. Our method combines and extends some of the best techniques available in the context of medical imaging. We express the deformation field as a B-spline model, which allows us to deal with a rich variety of deformations. ⋯ We provide an optimal analytical solution in the case when only landmarks and smoothness considerations are taken into account. We have applied our approach to perform the elastic registration of images such as electrophoretic gels and fly embryos. The validation of the results by experts has been favorable in all cases.