Abstracts

RATIONALE: With the interest and basic need to monitor the physiological condition (EEG) of animal models of epilepsy and stroke within the bore of high Tesla magnet fields, the traditional means of recording their EEG is not sufficient for quality recordings.
METHODS: We have adapted two EEG recording techniques to permit easy and viable recording of the animal[ssquote]s EEG while within the bore of up to 4.7T magnets. There are three main problems associated with the recording the EEG in the small bore of high field magnets. The first is physical confinement, as usually the bore is small and in addition, surface coils may be used so that the clearance between the top of the skull and the structures around the animal[ssquote]s head may be very restrictive. Second, the electrodes[ssquote] components and mass may significantly affect the quality of the images. Thirdly, the wires bringing the EEG signals out, the power in, or the presence of A/D convertors may be major sources of image artifact.
RESULTS: Two of these problems can be solved by using non-magnetic recording material such as silver, gold, or magnet grade copper. Instead of traditional metal skull screws, one can use a conductive-silver epoxy mix, formed into the blind burr hole along with insulated wire bared at the distal tip. Alternatively, and as a faster preparation, one can insert multi-stranded 0.1mm diameter Teflon insulated silver wire just under the skin; similar to the original chronic sphenoidal electrode technique developed for human use (1). Both these techniques create a reliable, low-profile EEG recording electrode preparation. These leads can then run to a miniature, closely positioned EEG preamplifier, located just in front of the animals nose in the bore of the magnet but outside the field of the MR pickup coil. The third problem can be solved by using battery operated electronics and analog multiplexed techniques driving non-conductive plastic fiber-optic leads to take the EEG signals out of the magnet[ssquote]s bore and shield to the recording area; as was initially developed for human EEG recording in magnetic fields (2). These fine silver wires can also be used to record the animal[ssquote]s EKG, EMG, or EOG if appropriately placed.
CONCLUSIONS: Simple and practical modification of the traditional EEG recording techniques can be adapted to permit neurophysiological information to be recording in the newer, harsher, confining environments of high magnetic field animal magnets.
References:
(1)Ives JR, Gloor P. New sphenoidal electrode assembly to permit long-term monitoring of the patient[ssquote]s ictal and interictal EEG. Electroenceph Clin Neurophysiol 1977; 42: 575-580.
(2)Ives JR, et al. Monitoring the patient[ssquote]s EEG during an MRI. Electroenceph. Clin. Neurophysiol. 1993; 87:417-420.
Disclosure: Equity - DigiTrace Care Services, Inc. Consulting - DigiTrace Care Services, Inc.; Stock - DigiTrace Care Services, Inc.; Royalties - DigiTrace Care Services, Inc.
Neuro Scan, Inc.