29 research outputs found
Kullback-Leibler and Renormalized Entropy: Applications to EEGs of Epilepsy Patients
Recently, renormalized entropy was proposed as a novel measure of relative
entropy (P. Saparin et al., Chaos, Solitons & Fractals 4, 1907 (1994)) and
applied to several physiological time sequences, including EEGs of patients
with epilepsy. We show here that this measure is just a modified
Kullback-Leibler (K-L) relative entropy, and it gives similar numerical results
to the standard K-L entropy. The latter better distinguishes frequency contents
of e.g. seizure and background EEGs than renormalized entropy. We thus propose
that renormalized entropy might not be as useful as claimed by its proponents.
In passing we also make some critical remarks about the implementation of these
methods.Comment: 15 pages, 4 Postscript figures. Submitted to Phys. Rev. E, 199
Quantitative analysis by renormalized entropy of invasive electroencephalograph recordings in focal epilepsy
Invasive electroencephalograph (EEG) recordings of ten patients suffering
from focal epilepsy were analyzed using the method of renormalized entropy.
Introduced as a complexity measure for the different regimes of a dynamical
system, the feature was tested here for its spatio-temporal behavior in
epileptic seizures. In all patients a decrease of renormalized entropy within
the ictal phase of seizure was found. Furthermore, the strength of this
decrease is monotonically related to the distance of the recording location to
the focus. The results suggest that the method of renormalized entropy is a
useful procedure for clinical applications like seizure detection and
localization of epileptic foci.Comment: 10 pages, 5 figure
Genetic and metabolic predictors of chemosensitivity in oligodendroglial neoplasms
The −1p/−19q genotype predicts chemosensitivity in oligodendroglial neoplasms, but some with intact 1p/19q also respond and not all with 1p/19q loss derive durable benefit from chemotherapy. We have evaluated the predictive and prognostic significance of pretherapy 201Tl and 18F-FDG SPECT and genotype in 38 primary and 10 recurrent oligodendroglial neoplasms following PCV chemotherapy. 1p/19q loss was seen in 8/15 OII, 6/15 OAII, 7/7 OIII, 3/11 OAIII and was associated with response (Fisher-Exact: P=0.000) and prolonged progression-free (log-rank: P=0.002) and overall survival (OS) (log-rank: P=0.0048). Response was unrelated to metabolism, with tumours with high or low metabolism showing response. Increased 18F-FDG or 201Tl uptake predicted shorter progression-free survival (PFS) in the series (log-rank: 201Tl P=0.0097, 18F-FDG P=0.0170) and in cases with or without the −1p/−19q genotype. Elevated metabolism was associated with shorter OS in cases with intact 1p/19q (log-rank: 18F-FDG P=0.0077; 201Tl P=0.0004) and shorter PFS in responders (log-rank: 18F-FDG P=0.005; 201Tl P=0.0132). 201Tl uptake and 1p/19q loss were independent predictors of survival in multivariate analysis. In this initial study, 201Tl and 18F-FDG uptake did not predict response to PCV, but may be associated with poor survival following therapy irrespective of genotype. This may be clinically useful warranting further study