Biomedical subjects

Sabine Van Huffel

Publications and source records attributed to Sabine Van Huffel.

6 recordsLinked to original sources

PubMed2003

Nonlinear analysis of heart rate variability in infants with apparent life-threatening events.

Some studies have shown that neonates having experienced an Apparent Life-Threatening Event (ALTE) have an increased risk of dying of the Sudden Infant Death Syndrome (SIDS). In this study the heart rate variability in neonates has been analyzed through a study of the long range correlations and scale invariance (self-similarity) in their cardiac rhythm. The goal is to see whether it is possible to distinguish normal infants from infants with ALTEs using the previously mentioned nonlinear measures of the heart rate variability. Twelve ALTE infants are included in this study. To determine the degree to which these neonates suffer from ALTEs two examinations are performed: a polysomnography and home monitoring. Using the nonlinear measures obtained from the nonlinear analysis of the heart rate variability, the group suffering most from ALTEs can clearly be separated from the other neonates.

Heart↗

PubMed2003

Measurement of tissue oxygenation index during the first three days in premature born infants.

No normal values of tissue oxygenation index (TOI) of the brain are known regarding premature born infants. We measured TOI, a measure for the cerebral hemoglobin oxygen saturation, on the head of 15 preterm infants with a median postmenstrual age of 28 weeks (interquartile range (IQR) between 26-29 weeks) with spatially resolved spectroscopy (NIRO 300, Hamamatsu) during the first three days of life. Infants with intra-ventricular hemorrhage or periventricular leucomalacia before the first measurement, as shown by ultrasound, were excluded. The first measurement was done within the first 6 hours of life, the second and third measurement at, respectively, 24 and 48 hours after this first measurement. The mean TOI was calculated if saturation did not change by more than 5% for at least 30 minutes. Other parameters measured were PaO2, PCO2, pH, mean arterial blood pressure, heart rate, hemoglobin, glycemia and peripheral oxygen saturation. There was a significant increase of TOI after 24 (p < 0.05) and 48 (p < 0.001) hours. The median TOI on the first day was 57% (95% CI: 54-65.7), 66.1% on the second day (95%CI: 61.9-82.3%) and 76.1% on the third day (95%CI 67.8-80.1%). No correlation was found between TOI and peripheral oxygen saturation, blood pressure, PaO2, PaCO2 and hemoglobin concentration after multiple regression analysis. TOI increases in the first three days in premature born babies. The increase of TOI is not due to an increase of oxygenation or mean arterial blood pressure. In our opinion, it reflects the increase in cerebral blood flow during the first three days.

Adult↗

PubMed2003

Quantitation of the concordance between cerebral intravascular oxygenation and mean arterial blood pressure for the detection of impaired autoregulation.

Since some important forms of brain injury in premature infants are caused in considerable part by disturbances in cerebral blood flow (CBF), it is important to be able to detect whether the cerebrovascular autoregulation, the mechanism by which CBF is maintained constant despite alterations in mean arterial blood pressure (MAP), is working properly. A recent study suggested that concordant changes in MAP and cerebral intravascular oxygenation (HbD), measured non-invasively by near-infrared spectroscopy (NIRS) as the difference between the concentration changes of oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (Hb), reflect impaired cerebrovascular autoregulation. Consequently, premature infants with impaired cerebrovascular autoregulation could be identified by simultaneous, continuous measurements of HbD and MAP. From several premature babies, MAP, HbD and arterial oxygen saturation (SaO2) were measured simultaneously at the University Hospital Leuven, Belgium. The concordance between MAP and HbD was quantitated using three different measures, among which a newly developed measure that looks for similarity of the dynamics between signals. Some preliminary results obtained from the measured data are given.

Blood Pressure↗

PubMed2003

Ultrasound assessment of endometrial thickness and endometrial polyps in women on hormonal replacement therapy.

OBJECTIVE: This study was performed to evaluate the thickness and the sonographic features of the endometrium in postmenopausal women on hormone replacement therapy (HRT). STUDY DESIGN: This prospective study was based on 483 vaginal ultrasound examinations performed in 238 consecutive postmenopausal women on HRT. RESULTS: Endometrial polyps were diagnosed by ultrasound in 16.3% of the patients; 43.6% were asymptomatic. In the nonpolyp group, a significant difference in endometrial thickness between sequential and continuous schemes was found. In sequential HRT, a three-layer ultrasound pattern of the endometrium was seen in 47% of the women in the estrogen-alone phase of cycle versus 11% in the estrogen-progestogen phase. CONCLUSION: Patients on HRT need other reference values for endometrial thickness compared with postmenopausal women without HRT. In women on sequential HRT, a transvaginal sonographic evaluation performed in the estrogen-alone phase of cycle may optimize the accuracy for focal lesion detection. The significance of the incidental finding of polyps in an important number of asymptomatic women on HRT remains unsettled.

Endometrial Neoplasms↗

PubMed2002

A subspace time-domain algorithm for automated NMR spectral normalization.

Recently, two methods have been proposed for quantitatively comparing NMR spectra of control and treated samples, in order to examine the possible occurring variations in cell metabolism and/or structure in response to numerous physical, chemical, and biological agents. These methods are the maximum superposition normalization algorithm (MaSNAl) and the minimum rank normalization algorithm (MiRaNAl). In this paper a new subspace-based time-domain normalization algorithm, denoted by SuTdNAl (subspace time-domain normalization algorithm), is presented. By the determination of the intersection of the column spaces of two Hankel matrices, the common signal poles and further on the components having proportionally varying amplitudes are detected. The method has the advantage that it is computationally less intensive than the MaSNAl and the MiRaNAl. Furthermore, no approximate estimate of the normalization factor is required. The algorithm was tested by Monte Carlo simulations on a set of simulation signals. It was shown that the SuTdNAl has a statistical performance similar to that of the MiRaNAl, which itself is an improvement over the MaSNAl. Furthermore, two samples of known contents are compared with the MiRaNAl, the SuTdNAl, and an older method using a standard. Finally, the SuTdNAl is tested on a realistic simulation example derived from an in vitro measurement on cells.

Journal Article↗

PubMedDate not supplied

Automatic frequency alignment and quantitation of single resonances in multiple magnetic resonance spectra via complex principal component analysis.

Several algorithms for automatic frequency alignment and quantitation of single resonances in multiple magnetic resonance (MR) spectra are investigated. First, a careful comparison between the complex principal component analysis (PCA) and the Hankel total least squares-based methods for quantifying the resonances in the spectral sets of magnetic resonance spectroscopy imaging (MRSI) spectra is presented. Afterward, we discuss a method based on complex PCA plus linear regression and a method based on cross correlation of the magnitude spectra for correcting frequency shifts of resonances in sets of MR spectra. Their advantages and limitations are demonstrated on simulated MR data sets as well as on an in vivo MRSI data set of the human brain.

Brain↗