Gradient coil power supply and imaging method

Apparatus for generating a magnetic field for magnetic resonance imaging, said apparatus comprising:

• a first resonant circuit including a first capacitive element electrically connected to a first current-carrying gradient coil to provide a first current flow path between said first capacitive element and said first gradient coil for generating a magnetic field gradient waveform;
• means for driving said first resonant circuit to generate a first sinusoidal segment at a first frequency;
• and
• means for driving said first resonant circuit to generate a second sinusoidal segment at a second frequency different from said first frequency, said second sinusoidal segment being a half-period cosine segment having a non-zero starting phase.

A method of generating a magnetic field for magnetic resonance imaging, said method comprising the steps of:

• providing a resonant circuit including a capacitive element electrically connected to a current-carrying gradient coil to provide a current flow path between said capacitive element and said gradient coil for generating a magnetic field gradient waveform;
• driving said resonant circuit to generate a first sinusoidal segment at a first frequency;
• and
• driving said resonant circuit to generate a second sinusoidal segment at a second frequency different from said first frequency immediately after said first sinusoidal segment, said second sinusoidal segment being a half-period cosine segment having a non-zero starting phase.

Circuitry for generating a magnetic field in a magnetic resonance imaging system, said circuitry comprising:

• a resonant power supply including:
• an amplifier;
• a current-carrying gradient coil electrically connected to said amplifier;
• a first capacitive element electrically connected to said amplifier through a switch, said switch having a closed state in which a first current flow path is provided between said first capacitive element and a first terminal of said amplifier, and said switch having an open state in which said first current flow path is interrupted;
• and
• a second capacitive element electrically connected to said amplifier through a bridged network, said bridged network having a first closed state in which a second current flow path is provided between a first terminal of said second capacitive element and said first terminal of said amplifier, said bridged network having a second closed state in which a third current flow path is provided between a second terminal of said second capacitive element and said first terminal of said amplifier, and said bridged network having an open state in which said second current flow path and said third current flow path are interrupted.