MRI method and apparatus for increasing the efficiency of echo lanar imaging and other late echo techniques

A method of determining a magnetic resonance imaging sequence, said magnetic resonance imaging sequence being of a type employing an RF excitation pulse in conjunction with a plurality of phase encoding gradient pulses and a cyclically switched frequency encoding gradient to produce an echo train, said magnetic resonance imaging sequence being further of a type utilizing late echos of said echo train, said method comprising:

• (a) inputting the user selectable sequence, resolution, and contrast parameters to define a prototype MR acquisition sequence defining a pattern of application of the RF excitation pulse, the plurality of phase encoding gradient pulses, and the cyclically switched frequency encoding gradient, and a first data acquisition period for acquiring k-space data, the first data acquisition period temporally coextensive with the application of the plurality of phase encoding gradient pulses and the cyclically switched frequency encoding gradient;
• (b) analyzing the prototype MR acquisition sequence to determine whether there exists a dead time period between application of the RF excitation pulse and the data acquisition period;
• and
• (c) if there exists a dead time period between application of the RF excitation pulse and the data acquisition period, defining a refined prototype acquisition sequence and a second data acquisition period wherein k-space data is collected during at least a portion of the dead time period.

A magnetic resonance imaging apparatus comprising:

• (a) magnets for creating a temporally constant magnetic field through an examination region;
• (b) at least one radio frequency coil assembly disposed adjacent the examination region for transmitting radio frequency signals into the examination region and for receiving magnetic resonance signals emanating from the examination region;
• (c) a transmitter connected with the at least one radio frequency coil assembly for supplying radio frequency pulses thereto;
• (d) a plurality of gradient coils disposed adjacent the examination region for creating magnetic field gradients across the examination region;
• (e) gradient pulse amplifiers connected with the gradient coils for applying current pulses to the gradient coils for selectively creating magnetic field gradients across the examination region;
• (f) an imaging sequence control connected with the transmitter and the gradient amplifiers, the imaging sequence control comprising:
• (i) control logic receiving user selectable sequence, resolution, and contrast parameters to define a prototype MR acquisition sequence and a first data acquisition period for acquiring k-space data, the prototype MR acquisition sequence defining a pattern of application of an RF excitation pulse and a plurality of phase encoding gradient pulses cyclically switched frequency encoding gradient, the first data acquisition period being temporally coextensive with the application of the plurality of phase encoding gradient pulses and the frequency encoding gradient;
• (ii) control logic analyzing the prototype MR acquisition sequence and measuring a dead time period between application of the RF excitation pulse and the data acquisition period;
• and (iii) control logic defining a refined prototype acquisition sequence and a second data acquisition period in which k-space data is collected during at least a portion of the dead time period;
• (g) a receiver that receives and demodulates the magnetic resonance signal to obtain phase encoded data lines;
• and
• (h) an image reconstruction processor for reconstructing the data lines into an electronic image representation.