Flow imaging using balanced phase contrast steady state free precession magnetic resonance imaging

A method for obtaining motion signals in an object comprising the steps of:

• a) placing the object in a static magnetic field,
• b) applying an rf magnetic excitation to the object,
• c) concurrently with and after step b) applying to the object a slice selection gradient having positive and negative values,
• d) after step b) applying to the object a phase encoding gradient,
• e) or step d) reading magnetic resonance signals for the selected slice,
• f) after step e) applying an inverted phase encoding gradient and an inverted readout and slice sole n gradient for zeroth and first order moment nulling,
• g) steps a) through f) with the positive and negative values of the slice selection gradient in step c) being inverted, and
• h) processing the magnetic resonance signals read in step c) and read in step g) to obtain motion signals.

A method of acquiring signal for motion in an object using magnetic resonance imaging, said method comprising the steps of:

• a) acquiring first signals from using a first readout gradient and a first phase encoding gradient,
• b) acquiring second signals using a second readout gradient and a second phase encoding gradient which is an inversion of the first readout gradient whereby the two readout gradients have different first moments and
• c) obtaining signals of motion through from the first signals and second signals depending on the difference in phase between the first signals and the second signals, the signals of motion being proportional to differences in the first moments of the readout gradient and proportional to motion in the readout direction, and wherein the phase difference in these signals Δφ(r) is related to the velocity component vz(r) in the readout direction and moments M1+ and M1− as follows:
• Δφ(r)=vz(r)γ[M1+−M1−]=2γM1+vz(r),
• with M 1 = ∫ 0 TE ⁢ G z ⁡ ( τ ) ⁢ τ ⁢ ⁢ ⅆ τ ,
• where γ is the gyromagnetic ratio.