Peter Van Leeuwen

Learn More
We exploit time reversibility analysis, checking the invariance of statistical features of a series after time reversal, to detect temporal asymmetries of short-term heart period variability series. Reversibility indexes were extracted from 22 healthy fetuses between 16th to 40th wk of gestation and from 17 healthy humans (aged 21 to 54, median=28) during(More)
The integrated exposure uptake biokinetic model for lead in children was developed to provide plausible blood lead distributions corresponding to particular combinations of multimedia lead exposure. The model is based on a set of equations that convert lead exposure (expressed as micrograms per day) to blood lead concentration (expressed as micrograms per(More)
BACKGROUND The prenatal condition offers a unique possibility of examining physiological interaction between individuals. Goal of this work was to look for evidence of coordination between fetal and maternal cardiac systems. METHODS 177 magnetocardiograms were recorded in 62 pregnancies (16th-42nd week of gestation). Fetal and maternal RR interval time(More)
The purpose of this study was to expand classic heart period analysis methods by techniques from ethnomusicology that explicitly take complex musical rhythm principles into consideration. The methods used are based on the theory of African music, the theory of symbolic dynamics, and combinatorial theory. Heart period tachograms from 192 24-h(More)
BACKGROUND AND AIM Fetal behavioural states have been defined on the basis of eye movements, body movements and heart rate patterns as presented by cardiotocography (CTG). The aim of this work was to determine whether behavioural states can be distinguished on the basis of heart rate features alone using high resolution beat-to-beat fetal(More)
The neurochemical environment of nontumorous white matter tissue was investigated in 135 single voxel spectra of "healthy" white matter regions of 43 tumor patients and 129 spectra of 52 healthy subjects. Spectra were acquired with short TE and TR values. With the data of tumor patients, it was examined whether differences were caused by the tumor itself or(More)
Pregnant mothers often report a special awareness of and bonding with their unborn child. Little is known about this relationship although it may offer potential for the assessment of the fetal condition. Recently we found evidence of short epochs of fetal-maternal heart rate synchronization under uncontrolled conditions with spontaneous maternal breathing.(More)
Dynamic aspects of R-R intervals have often been analyzed by means of linear and nonlinear measures. The goal of this study was to analyze binary sequences, in which only the dynamic information is retained, by means of two different aspects of regularity. R-R interval sequences derived from 24-h electrocardiogram (ECG) recordings of 118 healthy subjects(More)
BACKGROUND The univariate approaches used to analyze heart rate variability have recently been extended by several bivariate approaches with respect to cardiorespiratory coordination. Some approaches are explicitly based on mathematical models which investigate the synchronization between weakly coupled complex systems. Others use an heuristic approach,(More)
AIMS There is some dispute over the clinical significance of dispersion of ventricular repolarization measurements from the electrocardiogram. Recent studies have indicated that multichannel magnetocardiograms (MCGs), which non-invasively measure cardiac magnetic field strength from many sites above the body surface, may provide independent information from(More)