Steady-state imaging sequence

A method of magnetic resonance including:

• disposing a subject in an imaging region;
• repeatedly tipping magnetic resonance into a transverse plane to establish a steady-state;
• applying gradient pulses that define a closed sampling trajectory through a k-space starting at an origin point, the sampling trajectory returning to the origin point;
• sampling and demodulating signals from the magnetic resonance along at least a portion of the trajectory;
• monitoring demodulated signals sampled at the origin point;
• analyzing the demodulated signals sampled at the beginning and the end of each sampling trajectory to determine whether the trajectory actually returned to the origin point;
• in response to determining that the trajectory failed to return to the origin point, applying additional gradient pulses that return the trajectory to the origin point;
• reconstructing an image representation from the demodulated signals.

A method of magnetic resonance imaging comprising:

• disposing a subject in an imaging region;
• repeatedly tipping magnetic resonance into a transverse plane to establish a steady-state;
• applying oscillating gradient pulses along at least two axes which cause the trajectory to sample k-space densely around the origin point and less densely away from the origin point, the sampling trajectory returning to the origin point;
• demodulating resonance signals from the magnetic resonance along at least the more and less densely sampled regions of k-space;
• reconstructing data sampled along the more densely sampled region of k-space into a first image representation and data collected along less densely sampled region of k-space into a second image representation.

A magnetic resonance apparatus comprising:

• a magnet assembly which generates a temporally constant main magnetic field through an examination region;
• a gradient coil subsystem that applies gradient pulses to the examination region, the pulses defining a sampling trajectory through k-space, the trajectory oversampling at least one point;
• an RF subsystem which repeatedly tips magnetic resonance into a transverse plane and establishes a coherent steady-state in dipoles of a subject disposed in the examination region;
• a sampling circuit which samples magnetic resonance in the examination region;
• at least one radio frequency receiver for demodulating the sampled resonance signals;
• a processor which receives and analyzes the demodulated signals corresponding to the oversampled point for differences therebetween;
• a reconstruction processor which reconstructs the demodulated resonance signals into an image representation.

A magnetic resonance apparatus comprising:

• a magnet assembly which generates a temporally constant main magnetic field through an examination region;
• a gradient coil subsystem that applies gradient pulses to the examination region, the pulses defining a sampling trajectory through k-space, the trajectory oversampling at least one point;
• an RF subsystem which excites resonance in dipoles of a subject disposed in the examination region;
• a sequence controller that controls the gradient coil subsystem and the RF subsystem such that the trajectory sequence through k-space is a closed path that starts at the oversampled point and is projected to end at the oversampled point;
• at least one radio frequency receiver for demodulating sampled resonance signals;
• a processor which receives and analyzes the demodulated signals corresponding to the oversampled point for differences therebetween, the processor signalling which signals the sequence controller in response to the analysis of the oversampled points to control the gradient coil subsystem to apply additional gradient pulses until the trajectory returns to and ends at the oversampled point;
• a reconstruction processor which reconstructs the demodulated resonance signals into an image representation.

A method of steady-state magnetic resonance imaging, the method comprising:

• defining a sampling trajectory which starts at an origin point and continues along a closed path to an end point;
• sampling data along the trajectory at the origin point, the end point, and at least one section of the trajectory;
• reconstructing the data sampled along the section of the trajectory into an image representation;
• comparing the data sampled at the origin point with the data sampled at the end point.

A method of steady state magnetic resonance imaging comprising:

• applying gradients that define a sampling trajectory which starts at an origin point and continues along a closed path to an end point;
• sampling data along the trajectory at the origin point, approaching the end point, and at least one section of the trajectory;
• comparing the data sampled at the origin point with the data sampled at the end point;
• continuing to apply gradients and sample until the end point coincides with the origin;
• reconstructing the data sampled along the section of the trajectory into an image representation.