Magnetic resonance imaging apparatus

A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in an measurement space in which a static field is formed, and reconstructs an image on the basis of the MR signal, comprising:

• a sealed vessel housing the gradient field coil;
• a pump for exhausting internal air from said sealed vessel;
• and
• a noise gage for detecting a noise level in the measurement space.

A magnetic resonance imaging apparatus which generates an MR signal from an object by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field, and reconstructs an image on the basis of the MR signal, comprising:

• a sealed vessel housing the gradient field coil;
• a pump for exhausting internal air from said sealed vessel;
• a gradient field power supply for supplying a current to said gradient field coil;
• and
• a control circuit for controlling said gradient field power supply to change a gradient of a leading edge of the current or a rise time of the current.

A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

• a pump for exhausting internal air from said sealed vessel;
• means for driving the gradient field coil and high-frequency coil to generate an MR signal from an object in accordance with an arbitrarily set imaging condition and acquire the MR signal;
• and
• a pump control section for changing a driving pattern of said pump in accordance with the imaging condition.

A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

• a pump for exhausting internal air from said sealed vessel;
• a control section for driving the gradient field coil and high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences in order to generate an MR signal from an object and acquire the MR signal;
• and
• a pump control section for changing an ON time of said pump in accordance with the selected pulse sequence.

A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

• a pump for exhausting internal air from said sealed vessel;
• a control section for driving the gradient field coil and high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences in order to generate an MR signal from an object and acquire the MR signal;
• and
• a pump control section for driving said pump when the selected pulse sequence is a first pulse sequence, and stopping said pump when the selected pulse sequence is a second pulse sequence.

A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

• a shim coil for correcting a strength distribution of the static field;
• a vacuum gage for detecting a degree of vacuum in the sealed vessel;
• and
• means for changing a current supplied to said shim coil, on the basis of the detected degree of vacuum.

A magnetic resonance imaging apparatus including a static field magnet, a gradient field coil, a high-frequency coil, and a sealed vessel housing the gradient field coil, comprising:

• a pump for exhausting internal air from the sealed vessel;
• a vacuum gage for detecting a degree of vacuum in the sealed vessel;
• and
• a pump control section for controlling driving of said pump on the basis of the detected degree of vacuum such that the degree of vacuum in the sealed vessel becomes not more than about 3 mmHg (0.7 kPa).