Identification of the mammalian homologues of the Drosophila timeless gene, Timeless1 |
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Authors: | N Koike A Hida R Numano M Hirose Y Sakaki H Tei |
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Affiliation: | Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania, USA. |
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Abstract: | MRI systems often use magnetic field gradient and shim pulse-shaping networks (pre-emphasis) to correct for magnetic field distortions caused by eddy currents. A pre-emphasis system that uses up to 16 fixed resistor-capacitor (RC) time constants per channel with programmable amplitude coefficients is described. The magnetic fields induced by the pre-emphasis RC time constants serve as a set of basis functions for compensating eddy-current fields induced by the gradient set. The resultant time-varying magnetic field gradient accurately reflects the gradient specified by the pulse programmer. Reductions in eddy-current fields are demonstrated for actively shielded and unshielded gradient sets. |
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