Switchable birdcage coil
First Claim
1. An NMR birdcage coil switchably operating in a transmit and a receive modes comprising:
- a plurality of identical cells connected in a ladder pattern, each cell having an upper and a low ring reactive elements interconnected therebetween by a leg reactive element, anda complementary reactive element having leads switchably connecting to said reactive elements of one or more cells and forming a parallel resonant circuit therewith for switching said reactive elements from a normal reactive impedance state to a higher impedance state during the receive mode of operations.
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Accused Products
Abstract
A switchable birdcage coil functioning as a transmitter coil and a separate RF surface coil functioning as the receiver coil are utilize in NMR and MRI apparatus. To prevent the switchable birdcage coil from absorbing energy by coupling to the receiver coil or by absorbing power from the RF field produced by the precessing nuclear spins, one or more of the reactive elements of the birdcage coil are switched from a normal reactive impedance state to a high impedance state. The high impedance state is formed by switchably combining the reactive element with a complementary reactive element thereby forming parallel resonant high impedance circuit that is tuned to resonate at the NMR frequency.
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Citations
15 Claims
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1. An NMR birdcage coil switchably operating in a transmit and a receive modes comprising:
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a plurality of identical cells connected in a ladder pattern, each cell having an upper and a low ring reactive elements interconnected therebetween by a leg reactive element, and a complementary reactive element having leads switchably connecting to said reactive elements of one or more cells and forming a parallel resonant circuit therewith for switching said reactive elements from a normal reactive impedance state to a higher impedance state during the receive mode of operations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of switching a NMR birdcage coil between a transmit and a receive modes of operation, said NMR birdcage coil comprising a plurality of identical cells connected in a ladder pattern, each cell having an upper and a lower ring reactive elements interconnecting by a leg reactive element, comprising:
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providing a complimentary reactive element to one or more reactive elements; switchable connecting one of said cell reactive elements to the complimentary reactive element forming a parallel resonant circuit therewith; and switching the mode of operation of the birdcage coil from the transmit to the receive mode by tuning said parallel resonant circuit to a frequency of the NMR signals for forming a high impedance circuit and inactivating the birdcage coil. - View Dependent Claims (12, 13, 14, 15)
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Specification