Detection of late epilepsy by the texture analysis of MR brain images in the lithium-pilocarpine rat model

Abstract

The aim of the study was to detect by texture analysis non easily visible anomalies of magnetic resonance (MR) images of piriform and entorhinal cortices relevant to the lithium-pilocarpine (Li-Pilo) model of temporal lobe epilepsy in rats. Status epilepticus was induced by Li-Pilo in twenty male rats 21 day-old. T 2-weighted MR images of their brain, were obtained before injection of Li-Pilo and one day after status epilepticus. An hyperintense signal was found in the piriform and entorhinal cortices of six rats, which developed chronic epilepsy after a latent period of one to three months. Among the 14 other rats which displayed images similar to those obtained before injection, four remained healthy but 10 rats developed late epileptic symptoms, raising the problem of hidden cortical damage which may be too subtle to be detected by classic MRI examination. A numeric treatment of digital images was then undertaken by texture analysis, to derive image information from a purely computational point of view. The combined texture and discriminant analyses based on pixels pattern anomalies, selected 3 texture parameters derived from co-occurrence matrix which characterized structural abnormalities relevant to the hyperintense signal, not only in the modified images of 6 rats but also in images of 10 rats with apparently non modified images. These three texture’s parameters allowed to classify the twenty rats of our experiment as follows: sixteen epileptic rats were effectively classified with cortical lesions, two non epileptic were correctly classified with healthy cortex, but two healthy rats were not correctly classified. This misclassification is discussed on the basis of the time dependence of the onset of seizure in the Li-Pilo model. These promising results suggest to apply this method to MRI examinations for an improvement of the early diagnostic of human epilepsy.