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Biomedical subjects

C J Stok

Publications and source records attributed to C J Stok.

7 recordsLinked to original sources
PubMed1989

Statistical analysis of fever interval data.

Periodic fever syndromes usually do not show a clear fixed periodicity, and hence cannot be described by the mean and the standard deviation of the interval length. In those cases statistical tools must be used. Fever interval data can be described as a random point process; the renewal density function and its Fourier transform can be used to uncover hidden periodicities. In this report the estimation and evaluation of the renewal density function are described. The data of three patients with periodic fever were investigated. In one of these patients, suffering from periodic fever originating at the level of the hypothalamus, a 30-day periodicity was observed. In a female patient with hyperimmunoglobulinaemia D and periodic fever, menstruation often coincided with or was preceded by a fever episode. In the third patient with a Familial Hibernian Fever-like syndrome, an irregular fever pattern and no periodicity were found. The computerized analysis of the fever intervals may be useful in assessing various periodic fever syndromes.

Adult↗
PubMed1987

Inverse solutions based on MEG and EEG applied to volume conductor analysis.

An inverse solution computer program, using a single current dipole in a selected volume conductor, calculates an equivalent dipole from a magneto- or electroencephalographic distribution. The program is used to evaluate several volume conductor models of the head by using one model when generating the distribution and another when calculating the equivalent dipole. Sources of errors in the equivalent dipole, namely uncertainties in the model parameters (e.g. conductivities) and noise in the MEG or EEG distribution, are investigated in the same way. A realistically shaped model of the head is introduced to investigate the extent to which sphere-shaped models can be used.

Adult↗
PubMed1986

Model evaluation using electroencephalography and magnetoencephalography.

The source of both the measured visual evoked potentials and the measured visual evoked magnetic fields was estimated by means of an inverse procedure. The model used consisted of a single current dipole positioned in a volume conductor consisting of four concentric spheres. Comparison of the results showed that the estimations did not always match. In order to reveal a possible cause of this mismatch a realistically shaped multicompartment model of the head was constructed. From forward simulations it followed that the influence of the realistic shape was apparent, especially when the dipole was positioned deep within the brains.

Electroencephalography↗