Detuning circuit and detuning method for an MRI system

A detuning circuit for detuning an RF receive coil during the transmit phase in a magnetic resonance imaging system having a transmit phase and a receive phase, the detuning circuit including

• e1) a resonance circuit including a detuning capacitor and a detuning inductor;
• e2) a PIN diode coupled in series to said detuning inductor and together with said detuning inductor in parallel communication with said detuning capacitor for enabling or disabling the resonance circuit;
• e3) a bias current generating circuit for generating a DC bias current through the PIN diode during the transmit phase including:
• e31) a rectifier coupled, with the same serial polarity, in parallel to the PIN diode,
• e32) a current limiting circuit coupled in series to said rectifier and together with said rectifier in parallel communication with said detuning capacitor for passing a small current through the rectifier, and
• e33) a reactive circuit coupled between the common node of the detuning inductor and the PIN diode and the common node of the rectifier and the current limiting circuit for passing a DC current between said common nodes.

A magnetic resonance imaging method having a transmit phase and a receive phase, the method comprising the steps of:

• a) generating a main magnetic field through an imaging region;
• b) generating magnetic field gradients across the main magnetic field;
• c) selectively transmitting an RF transmit pulse having a resonance frequency spectrum through the imaging region during the transmit phase, exciting nuclei in the imaging region to generate magnetic resonance signals in the resonance frequency spectrum;
• d) receiving magnetic resonance signals during the receive phase by a RF receive coil;
• and
• e) detuning the RF receive coil during the transmit phase, the detuning circuit including
• e1) generating a resonance by a resonance circuit including a detuning capacitor and a detuning inductor;
• e2) enabling or disabling the resonance circuit a PIN diode coupled in series to said detuning inductor and together with said detuning inductor in parallel communication with said detuning capacitor;
• e3) generating a DC bias current through the PIN diode during the transmit phase by a bias current generating circuit including:
• e31) a rectifier coupled, with the same serial polarity, in parallel to the PIN diode,
• e32) a current limiting circuit coupled in series to said rectifier and together with said rectifier in parallel communication with said detuning capacitor for passing a small current through the rectifier, and
• e33) a reactive circuit coupled between the common node of the detuning inductor and the PIN diode and the common node of the rectifier and the current limiting circuit for passing a DC current between said common nodes.

A detuning method for detuning an RF receive coil during the transmit phase in a magnetic resonance imaging system having a transmit phase and a receive phase, the detuning method including the steps of

• e1) generating a resonance by a resonance circuit including a detuning capacitor and a detuning inductor;
• e2) enabling or disabling the resonance circuit a PIN diode coupled in series to said detuning inductor and together with said detuning inductor in parallel communication with said detuning capacitor;
• e3) generating a DC bias current through the PIN diode during the transmit phase by a bias current generating circuit including:
• e31) a rectifier coupled, with the same serial polarity, in parallel to the PIN diode,
• e32) a current limiting circuit coupled in series to said rectifier and together with said rectifier in parallel communication with said detuning capacitor for passing a small current through the rectifier, and
• e33) a reactive circuit coupled between the common node of the detuning inductor and the PIN diode and the common node of the rectifier and the current limiting circuit for passing a DC current between said common nodes.

A non-transitory computer readable medium comprising a computer program for detuning an RF receive coil during the transmit phase in a magnetic resonance imaging system having a transmit phase and a receive phase, the computer program including instructions for

• e1) generating a resonance by a resonance circuit including a detuning capacitor and a detuning inductor;
• e2) enabling or disabling the resonance circuit a PIN diode coupled in series to said detuning inductor and together with said detuning inductor in parallel communication with said detuning capacitor;
• e3) generating a DC bias current through the PIN diode during the transmit phase by a bias current generating circuit including:
• e31) a rectifier coupled, with the same serial polarity, in parallel to the PIN diode,
• e32) a current limiting circuit coupled in series to said rectifier and together with said rectifier in parallel communication with said detuning capacitor for passing a small current through the rectifier, and
• e33) a reactive circuit coupled between the common node of the detuning inductor and the PIN diode and the common node of the rectifier and the current limiting circuit for passing a DC current between said common nodes.