Comparison of active source estimated by dipole tracing method and PET in human brain.

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We have developed a computer-aided method to estimate the location and vector moment of an electric generator (e.g.a current dipole) in the human brain. Using the dipole-tracing (DT) system we developed and brought with us, we performed experiments on one patient and six normal volunteers at the Clinical Neurophysiology Laboratory of the Massachusetts General Hospital in Boston.1. localization of abnormal EEG: A patient showed a high amplitude slow wave EEG, which was augmented under hyperventilation, after cerebral hemmorrhage. The electric location of the slow wave was estimated using the DT system. Prior to the DT study, PET scanning was performed to measure the cerebral blood flow and oxygen consumption. The location estimated by the DT was compared with the PET images and NMR images. The electric location of the slow wave was estimated at the frontal cortical area of the affected side and corresponded with those of normal brain tissue revealed by NMR and relatively normal blood flow revealed by PET. But the reason why such a slow wave was generated in the patient still remained unsolved.2.Visual evoked potentials obtained from normal volunteers and analyzed by the DT system. A checker board pattern was presented at either reifht, left half or full field of one eye. The results obtained by the DT analysis corresponded well with the anatomical projection of the retinostriate system in human.