EPI data correction method and device and MRI system

An echo planar imaging (EPI) scanning method, comprising:

• in a single excited EPI scanning process, simultaneously applying a 90° radio-frequency (RF) excited pulse and a first layer selection gradient pulse to a target tissue in a layer selection encoding direction;
• after applying the RF excited pulse, simultaneously applying a first RF convergence pulse and a second layer selection gradient pulse to the target tissue in the layer selection encoding direction;
• after applying the first RF convergence pulse, simultaneously (i) applying a first readout gradient pulse sequence to the target tissue in a readout direction, and (ii) turning on an analog-digital converter (ADC) to collect data for correcting a phase error between k-space lines while forbidding phase encoding gradients in a phase encoding direction;
• and
• after applying the first readout gradient pulse sequence, turning off the ADC, and sequentially applying the first RF convergence pulse to the target tissue for 2R times at intervals, and applying the second layer selection gradient pulse to the target tissue in the layer selection encoding direction while the first RF convergence pulse is applied each time;
• after the first RF convergence pulse is applied each time, applying the first or second readout gradient pulse sequence to the target tissue in the readout direction, and simultaneously (i) applying a first phase encoding pulse sequence in the phase encoding direction, and (ii) turning on the analog-digital converter to collect auto calibration signal (ACS) data in a segmented manner,
• wherein R represents an in-layer phase direction acceleration factor,
• wherein the first readout gradient pulse sequence is applied to the target tissue at odd-numbered times in the 2R times,
• wherein the second readout gradient pulse sequence is applied to the target tissue at even-numbered times in the 2R times, each of the first and second readout gradient pulse sequence being formed by a plurality of pairs of gradient pulses with opposite polarities, and the polarity of the first readout gradient pulse sequence being opposite to that of the second readout gradient pulse sequence;
• and
• when the first or second readout gradient pulse sequence applied to the target tissue in the readout direction is when the polarity of the gradient pulse changes, applying a phase encoding pulse to the target tissue in the phase encoding direction.

An echo planar imaging (EPI) scanning method, comprising:

• in a single excited EPI scanning process, simultaneously applying a 90° radio-frequency (RF) excited pulse and a first layer selection gradient pulse to a target tissue in a layer selection encoding direction;
• after applying the RF excited pulse, simultaneously applying a first RF convergence pulse and a second layer selection gradient pulse to the target tissue in the layer selection encoding direction;
• after applying the first RF convergence pulse, simultaneously (i) applying a first readout gradient pulse sequence to the target tissue in a readout direction, and (ii) turning on an analog-digital converter (ADC) to collect data for correcting a phase error between k-space lines while forbidding phase encoding gradients in a phase encoding direction;
• and
• after applying the first readout gradient pulse sequence, turning off the ADC, sequentially applying the first RF convergence pulse to the target tissue for 2R times at intervals, and applying the second layer selection gradient pulse to the target tissue in the layer selection encoding direction while the first RF convergence pulse is applied each time;
• after the first RF convergence pulse is applied each time, applying the first readout gradient pulse sequence to the target tissue in the readout direction, and simultaneously (i) applying a second phase encoding pulse sequence in the phase encoding direction, and (ii) turning on the ADC to collect auto calibration signal (ACS) data in a segmented manner,
• wherein R represents an in-layer phase direction acceleration factor, and the first readout gradient pulse sequence is formed by a plurality of pairs of gradient pulses with opposite polarities;
• and
• when the first readout gradient pulse sequence applied to the target tissue in the readout direction is when adjacent pairs of gradient pulses are alternate, applying one phase encoding pulse to the target tissue in the phase encoding direction.

An echo planar imaging (EPI) scanning device, comprising:

• first data collection circuitry configured to cause the EPI scanning device to perform a single excited EPI scanning process by:
• simultaneously applying a 90° radio-frequency (RF) excited pulse and a first layer selection gradient pulse to a target tissue in a layer selection encoding direction;
• after applying the RF excited pulse, simultaneously applying a first RF convergence pulse and a second layer selection gradient pulse to the target tissue in the layer selection encoding direction;
• and
• after applying the first RF convergence pulse, simultaneously (i) applying a first readout gradient pulse sequence to the target tissue in a readout direction, and (ii) turning on an analog-digital converter (ADC) to collect data for correcting a phase error between k-space lines while forbidding phase encoding gradients in a phase encoding direction;
• and
• second data collection circuitry configured to cause the EPI scanning device to:
• after applying the first readout gradient pulse sequence, turn off the ADC, sequentially apply the first RF convergence pulse to the target tissue for R times at intervals, and apply the second layer selection gradient pulse to the target tissue in the layer selection encoding direction while the first RF convergence pulse is applied each time;
• after applying the first RF convergence pulse each time, simultaneously (i) apply the first readout gradient pulse sequence to the target tissue in the readout direction, (ii) apply a first phase encoding pulse sequence in the phase encoding direction, and (iii) turn on the ADC to collect auto calibration signal (ACS) data in a segmented manner,
• wherein R is an in-layer phase direction acceleration factor, and
• wherein the first readout gradient pulse sequence is formed by a plurality of pairs of gradient pulses with opposite polarities, and
• when the first readout gradient pulse sequence applied to the target tissue in the readout direction is when the polarity of the gradient pulse changes, apply a phase encoding pulse to the target tissue in the phase encoding direction.

An echo planar imaging (EPI) scanning device, comprising:

• third data collection circuitry configured to cause the EPI Scanning device to perform a single excited EPI scanning process, by:
• simultaneously applying a 90° radio-frequency (RF) excited pulse and a first layer selection gradient pulse to a target tissue in a layer selection encoding direction;
• after applying the RF excited pulse, simultaneously applying a first RF convergence pulse and a second layer selection gradient pulse to the target tissue in the layer selection encoding direction;
• and
• after applying the first RF convergence pulse, simultaneously (i) applying a first readout gradient pulse sequence to the target tissue in a readout direction, and (ii) turning on an analog-digital converter (ADC) to collect data for correcting a phase error between k-space lines while forbidding phase encoding gradients in a phase encoding direction;
• and
• fourth data collection circuitry configured to cause the EPI scanning device to:
• after applying the first readout gradient pulse sequence, turn off the ADC, sequentially apply the first RF convergence pulse to the target tissue for 2R times at intervals, and apply the second layer selection gradient pulse to the target tissue in the layer selection encoding direction while the first radio-frequency convergence pulse is applied each time;
• after applying the first RF convergence pulse each time, applying the first or second readout gradient pulse sequence to the target tissue in the readout direction, simultaneously (i) apply a first phase encoding pulse sequence in the phase encoding direction, and (ii) turn on the analog-digital converter to collect auto calibration signal (ACS) data in a segmented manner,
• wherein R represents an in-layer phase direction acceleration factor,
• wherein the first readout gradient pulse sequence is applied to the target tissue at odd-numbered times in the 2R times,
• wherein the second readout gradient pulse sequence is applied to the target tissue at even-numbered times in the 2R times, each of the first and second readout gradient pulse sequence being formed by a plurality of pairs of gradient pulses with opposite polarities, and the polarity of the first readout gradient pulse sequence being opposite to that of the second readout gradient pulse sequence;
• and
• when the first or second readout gradient pulse sequence applied to the target tissue in the readout direction is when the polarity of the gradient pulse changes, apply a phase encoding pulse to the target tissue in the phase encoding direction.

An echo planar imaging (EPI) scanning device, comprising:

• fifth data collection circuitry configured to cause the EPI scanning device to perform a single excited EPI scanning process by:
• simultaneously applying a 90° radio-frequency (RF) excited pulse to a target tissue and a first layer selection gradient pulse to a target tissue in a layer selection encoding direction;
• after applying the RF excited pulse, simultaneously applying a RF convergence pulse and a second layer selection gradient pulse to the target tissue in the layer selection encoding direction;
• and
• after applying the first RF convergence pulse, simultaneously applying a first readout gradient pulse sequence to the target tissue in a readout direction and turning on an analog-digital converter (ADC) to collect data for correcting a phase error between k-space lines while forbidding phase encoding gradients in a phase encoding direction;
• and
• sixth data collection circuitry configured to cause the EPI scanning device to:
• after applying the first readout gradient pulse sequence, turning off the ADC, sequentially applying the first RF convergence pulse to the target tissue for 2R times at intervals, and applying the second layer selection gradient pulse to the target tissue in the layer selection encoding direction while the first radio-frequency convergence pulse is applied each time;
• after applying the first RF convergence pulse each time, simultaneously applying (i) the first readout gradient pulse sequence to the target tissue in the readout direction, (ii) applying a phase encoding pulse sequence in the phase encoding direction, and (iii) turning on the analog-digital converter to collect auto calibration signal (ACS) data in a segmented manner,
• wherein R represents an in-layer phase direction acceleration factor, and the first readout gradient pulse sequence is formed by a plurality of pairs of gradient pulses with opposite polarities;
• and
• when the first readout gradient pulse sequence applied to the target tissue in the readout direction is when adjacent pairs of gradient pulses are alternate, applying a phase encoding pulse to the target tissue in the phase encoding direction.