Abstracts

It has been established that optical intrinsic signal (OIS) imaging correlates well with seizure activity. In this study, we obtained high-spatial-resolution images of normalized oxy-hemoglobin (Hb), deoxy-Hb, total Hb, oxygen saturation and oxygen-consumed maps of acute neocortical seizures in rats by using spectral images recorded simultaneously at multiple wavelengths., In 17 Spraque-Dawley rats, surgery and OIS imaging were performed under general anesthesia in a thinned skull preparation. OIS images were obtained with two CCD cameras with combination of two optical filters among 852, 780, 610 and 568 nm. Electroencephalography (EEG) was recorded in real time with multiple depth electrodes or Michigan 16-channel electrodes in the somatosensory cortex. OIS spectral images were synchronously recorded with EEG. Acute seizures were induced by penicillin applied topically. Images of oxy-Hb, deoxy-Hb, total Hb, oxygen saturation, oxygen-consumed and scattering maps were obtained by performing the following sequential numerical steps :1) ratio analysis, 2) image transformation and co-registration, 3) pixel-by-pixel calculation of normalized oxy-Hb, deoxy-Hb, total Hb, oxygen saturation and oxygen consumed using the Beer-Lambert law, 4) reconstruct normalized images., High-spatial-resolution normalized images of oxy-Hb, deoxy-Hb, total Hb, oxygen saturation and oxygen-consumed maps were reconstructed to study seizure induction and propagation. It was noted that before or at seizure onset, the concentration of deoxy-Hb transiently increases, in both parenchyma ([sim]0.03%) and venous space ([sim]0.06%). After that, it was quickly followed by increases of oxy-Hb in the parenchyma ([sim]0.03%) and venous space ([sim]0.06%)., By obtaining OIS spectral images of multiple wavelengths simultaneously, normalized high-spatial-resolution maps of oxy-Hb, deoxy-Hb, total-Hb and oxygen saturation could be reconstructed. Based on these maps, changes of oxy-Hb, deoxy-Hb and total-Hb could be reviewed with information of the anatomical structures. These maps showed initial increase of deoxy-Hb transiently in both parenchyma and venous space before seizure onset., (Supported by NINDS K08 NS 42798.)