Magnetic Resonance Imaging and the Epileptic Focus
Nuclear magnetic resonance provides us with a new imaging modality which can be used not only to analyze the structure and structural pathology, but also to some extent the pathophysiology of the central nervous system. A large magnetic field and radio frequency pulse sequences are used to generate a signal consisting of several basic parameters of nuclear magnetic resonance: (1)proton density, (2)Ti constant or spin-lattice (longitudinal) relaxation time, and (3)T2 constant or spin-spin (horizontal) relaxation time. The resulting signal can be weighted for each of the parameters by altering the radio frequency pulse sequences. The most commonly used sequences are called inversion recovery (IR), which emphasizes Tt constant and provides gray-white matter contrast, and spin echo (SE), which emphasizes T2 constant and shows pathology. The signal is spatially encoded and computerized in a manner similar to computerized tomography (CT). For a detailed description of the technique, see Lauterbur (1973) and Pykett et al. (1982).
KeywordsTemporal Lobe Temporal Lobe Epilepsy Spin Echo Seizure Focus Brain Water Content
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