Balun and magnetic resonance imaging apparatus

A magnetic resonance imaging apparatus, comprising,

• a static magnetic field generator which generates a static magnetic field,
• a gradient magnetic field generator which generates a gradient magnetic field,
• an RF magnetic field generator which generates an RF magnetic field,
• a transmit-receive coil which applies the RF magnetic field to a test subject and receives a magnetic resonance signal from the test subject,
• a signal processor which processes the magnetic resonance signal received from the transmit-receive coil,
• a transmit-receive switch which connects the RF magnetic field generator with the transmit-receive coil when the RF magnetic field is applied to the test subject and which connects the transmit-receive coil with the signal processor when the magnetic resonance signal received by the transmit-receive coil is processed, and
• a controller which controls the gradient magnetic field generator, the RF magnetic field generator, and the signal processor, wherein,
• the transmit-receive coil is connected with the transmit-receive switch via a coaxial cable, and
• the coaxial cable comprises a balun, the balun is connected to the coaxial cable and comprises:
• a parallel circuit connected in parallel with a shield of the part of the coaxial cable, wherein,
• the parallel circuit comprises multiple serial resonance circuits each connected in parallel,
• each of the multiple serial resonance circuits comprises a capacitor and an inductor being connected in series, and resonance frequencies of the respective serial resonance circuits are adjustable by capacitance of the capacitor and by inductance of the inductor, and
• at least one of the resonance frequencies of the multiple serial resonance circuits is adjusted to be lower than a frequency at which the balun blocks the common mode noise, and at least one of the resonance frequencies is adjusted to be higher than the frequency at which the balun blocks the common mode noise.

A magnetic resonance imaging apparatus, comprising,

• a static magnetic field generator which generates a static magnetic field,
• a gradient magnetic field generator which generates a gradient magnetic field,
• an RF magnetic field generator which generates an RF magnetic field,
• a transmit coil which applies the RF magnetic field to a test subject,
• a receive coil which receives a magnetic resonance signal from the test subject,
• a signal processor which processes the magnetic resonance signal received from the receive coil, and
• a controller which controls the gradient magnetic field generator, the RF magnetic field generator, and the signal processor, wherein,
• the magnetic resonance imaging apparatus further comprising,
• a first coaxial cable for transmitting the RF magnetic field formed by the RF magnetic field generator to the transmit coil, and
• a second coaxial cable for transmitting the magnetic resonance signal received by the receive coil to the signal processor, wherein,
• each of the first coaxial cable and the second coaxial cable comprises a balun, and
• the balun is connected to each of the first coaxial cable and the second coaxial cable and comprises:
• a parallel circuit connected in parallel with a shield of the part of the coaxial cable, wherein,
• the parallel circuit comprises multiple serial resonance circuits each connected in parallel,
• each of the multiple serial resonance circuits comprises a capacitor and an inductor being connected in series, and resonance frequencies of the respective serial resonance circuits are adjustable by capacitance of the capacitor and by inductance of the inductor, and
• at least one of the resonance frequencies of the multiple serial resonance circuits is adjusted to be lower than a frequency at which the balun blocks the common mode noise, and at least one of the resonance frequencies is adjusted to be higher than the frequency at which the balun blocks the common mode noise.