Automatic detuning of non-connected transceiver coils for MRI
Methods and a device for automatic detuning of a magnetic resonance tomography (MRT) local coil not connected to an MRT system are provided. The device has self-closing switches that are closed or open, depending on the presence of an MRT high-frequency field.
1. A device for automatic detuning of a magnetic resonance tomography (MRT) local coil of an MRT system, the device comprising:
a transceiver branch comprising self-closing switches that are automatically closed or open depending on the presence of an MRT high-frequency field, the self-closing switches being in communication with the MRT local coil,
wherein the MRT local coil comprises a connecting cable with a plug connectable to the MRT system, and wherein the MRT local coil is not connected to the MRT system via the connecting cable and plug during the detuning of the MRT local coil, and
wherein the MRT local coil is configured for transmitting RF transmit signals and for receiving RF receive signals.
2. The device as claimed in claim 1 , wherein the self-closing switches are configured so that, in a state with an MRT RF field present, the self-closing switches are closed by self-closing, and in a state without an MRT RF field, the self-closing switches are open.
3. The device as claimed in claim 1 , wherein an inductance conditional on a length of the connecting cable of the MRT local coil forms a resonant parallel circuit together with a coupling capacitor on the MRT local coil.
4. The device as claimed in claim 1 , wherein each of the self-closing switches is a PIN diode.
5. The device as claimed in claim 4 , wherein the PIN diode is a PIN diode self-powered by the MRT-RF field.
6. The device as claimed in claim 1 , wherein a switch of the self-closing switches is a switch that self closes for a strength of an MRT-RF field lying above a threshold value, the switch being open with a strength of an MRT-RF field lying below a threshold value.
7. The device as claimed in claim 1 , wherein in a state in which transmit signals to be transmitted to the MRT local coil from the MRT system are present, the self-closing switches in the form of PIN diodes are powered with a current, in a state in which the MRT local coil transmits receive signals to the MRT system, the self-closing switches in the form of PIN diodes are pre-set with an initial voltage, or a combination thereof.
8. The device as claimed in claim 7 , wherein the current is 100 mA, and wherein the initial voltage is −30 V.
9. The device as claimed in claim 1 , wherein the self-closing switches are a part of one or the only transceiver branch of the MRT local coil, the self-closing switches of the transceiver branch are the only switches configured for the automatic detuning of the MRT local coil not connected to the MRT system, or a combination thereof.
10. The device as claimed in claim 1 , wherein in a state in which the MRT local coil is transmitting receive signals to the MRT system, one or both of the self-closing switches are opened.
11. The device as claimed in claim 1 , wherein in a state in which the MRT local coil is transmitting receive signals to the MRT system, a preamplifier is directly connected via a series resonant circuit to an antenna.
12. The device as claimed in claim 1 , wherein in a state in which the MRT local coil is transmitting receive signals to the MRT system, no additional phase rotation is provided between an antenna and a preamplifier, a preamplifier decoupling, a zero-power reading out of the receive signals, or the preamplifier decoupling and the zero-power reading out of the receive signals are provided, or any combination thereof.
13. The device as claimed in claim 1 , wherein in a state in which the MRT local coil is receiving transmit signals to be transmitted from the MRT system, both of the self-closing switches are closed, a preamplifier is isolated from an antenna, a coil is connected in parallel to an antenna input, or any combination thereof.
14. The device as claimed in claim 1 , wherein a capacitor is provided between a switch of the self-closing switches and an amplifier output of a preamplifier.
15. The device as claimed in claim 1 , wherein in a state in which the MRT local coil is receiving transmit signals to be transmitted from the MRT system, a coil and a capacitor form a parallel resonant circuit that is at high resistance, without influence on the transmission of the transmit signals, or a combination thereof.
16. The device as claimed in claim 1 , wherein an RF voltage generated by an MRT-high-frequency field is present between two coils connected in series with each other, the RF voltage being provided rectified for powering at least one PIN diode.
17. The device as claimed in claim 1 , further comprising a controller configured for active control of the self-closing switches, the controller being a controller of the MRT system, a controller of the MRT local coil, or a controller of the MRT system and the MRT local coil.
18. A magnetic resonance tomography (MRT) local coil comprising:
a connecting cable with a plug that is connectable to an MRT system; and
a device for automatic detuning of the MRT local coil when the MRT local coil is not connected to the MRT system via the connecting cable and the plug, the device comprising:
a transceiver branch comprising self-closing switches that are automatically closed or open depending on the presence of an MRT high-frequency field, the self-closing switches being in communication with the MRT local coil,
wherein the MRT local coil is configured for transmitting RF transmit signals and for receiving RF receive signals.
19. A method for automatic detuning of a local magnetic resonance tomography (MRT) coil of an MRT system, the method comprising:
closing self-closing switches when an MRT high-frequency field is present, the self-closing switches being in communication with the local MRT coil,
wherein the MRT local coil comprises a connecting cable with a plug that is connectable to the MRT system, and wherein the MRT local coil is not connected to the MRT system via the connecting cable and the plug during the detuning of the MRT local coil,
wherein the self-closing switches are open in the absence of the MRT high-frequency field, and
wherein the local MRT coil is configured for transmitting RF transmit signals and for receiving RF receive signals.