Simultaneously acquired BEG and BOLD (Blood Oxygenation level dependent contrast) MRI allowed to study on line the neurophysiological changes in rat brain during epileptic seizures. MRI aiid EEG data were acquired with a specially designed high quality MR RF-antenna with incorporated non-invasive carbon EEG electrodes. The problem of severe pollution of the BEG data due to MR gradient switching during simultaneous EEGIMRI acquisitions was solved by a specially designed automated effective filtering algorithm. We measured continuously EEG data, and T2 -weighted coronal MRI sections of rat brain before and after the injection of penteirazol (43mg1(kg body weight) PTZ; convulsive dose 97%), an epilepsy inductor. In this way, we could correlate the abnormalities in the EEG traces, with changes in the MRJ BOLD signal intensities. Immediately after PTZ induction and before epileptic discharges were observed on the EEG traces, the cortex displayed an increase in BOLD signal intensity (increase in blood flow). Much later and correlated with epileptic discharges on the EEG traces, the ventromedial hypothalamic nuclei showed an increased BOLD signal while the BOLD signal intensity dropped in the entire brain, except for the hypothalamus. The decreased BOLD signal reflected general hypoxia and subsequent ischemia as a consequence ofthe sustained depolarization of neurons during the seizure.
During a Magnetic Resonance (MR) sequence, simultaneously acquired ElectroEncephaloGraphy (EEG) data are compromised by severe pollution due to artifacts originating from the switching of the magnetic field gradients. In this work, it is shown how these artifacts can be strongly reduced or even removed through application of an adaptive artifact restoration scheme. The method has proved to be fully automatic and to retain high frequency EEG information, which is indispensable for many EEG applications.
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