A method of minimizing dead-periods in magnetic resonance imaging pulse sequences employs a specimen disposed within magnetic field, a source of RF signals, a receiver for receiving signals from the specimen responsive to RF pulses and emitting respective output signals. A computer is provided for receiving the output signals from the receiver and establishing image information which may be displayed. For the dead-period, the minimum and maximum phase encoding step, the scan plane gradient pulse for the slice, phase encoding and readout directions are determined and the moments contained within the dead-period waveform is determined. The values are transformed into gradient amplifier coordinates and the minimum dead-period based on a dead-period waveform is determined. The dead-period is employed in establishing a hardware optimized waveform which may be trapezoidal. The trapezoidal waveform is preferably established by for each phase encoding step determining the starting and ending gradient levels and the moments contained within the dead-period waveform and employing the waveform to design a trapezoidal waveform using the calculated minimum dead-period.
Technical Details:
Straightforward method to calculate maximum gradient amplitudes for the functions of frequency encode, phase encode, and section select in oblique MRI. The calculated amplitude values depend on the angulation of the prescription, and on which of the three functions are simultaneously active. The derived expressions are optimal in most cases, and when not optimal still offer substantial improvement compared to calculations that do not incorporate angular information. Both matrix-based and geometrical interpretations are presented.
