Method and device for driving a magnetic resonance imaging system
Inventors
Assignees
Publication Number
US-12352839-B2
Publication Date
2025-07-08
Expiration Date
2043-11-29
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Abstract
A method for driving a MRI system to generate MRI data of an examination subject may include performing an accelerated echoplanar imaging with an undersampling according to a pulse sequence diagram to acquire k-space data. The pulse sequence diagram may have a plurality of repetitions respectively including: a first sampling diagram configured for an acquisition of k-space data for Nyquist ghost correction, or to generate magnetic field maps, a subsequent second sampling diagram configured for an accelerated echoplanar acquisition, and an excitation diagram that is common to both acquisitions. The first sampling diagram of a real subset of the plurality of repetitions may be modified to: supplement the acquired k-space data using a supplementation of k-space data missing due the undersampling, and/or correct image space of artifacts occurring due to the undersampling based on the k-space data acquired with the modified first sampling diagram.
Core Innovation
The invention relates to a method, control device, and magnetic resonance imaging (MRI) system for driving the MRI system to generate magnetic resonance image data via an accelerated echoplanar imaging (EPI) with undersampling. The method involves acquiring k-space data according to a pulse sequence diagram comprising multiple repetitions, each including a first sampling diagram for acquiring data for Nyquist ghost correction or generating magnetic field maps, a second sampling diagram for accelerated echoplanar acquisition, and a common excitation diagram for both acquisitions.
The problem addressed is the long duration and patient discomfort associated with conventional MRI image acquisition due to the sequential nature of k-space data acquisition and necessary relaxation times. Artifacts arise in undersampled data acquired from accelerated imaging methods, such as in parallel imaging techniques. Conventional correction methods require separate acquisitions for reference data, increasing total scan time and patient inconvenience. The invention aims to enable time-saving EPI methods that reduce total acquisition time without extending repetition duration, while still allowing correction of artifacts and supplementation of missing data due to undersampling.
The core innovation is modifying the first sampling diagram in a real subset of the repetitions such that the acquired k-space data allow supplementation of missing k-space data due to the undersampling and/or correction of artifacts in image space caused by undersampling. The modification encodes the sampling with phase encoding gradients, acquiring additional k-space data as reference data for calibration or auto-calibration algorithms (e.g., GRAPPA, SENSE) integrated within the imaging sequence. This integration obviates separate acquisition of reference data, maintaining the repetition and echo times, preserving steady states of spins and reducing overall acquisition time. The method supports various accelerated imaging techniques including GRAPPA, SMS, combined GRAPPA+SMS, dual polarity imaging, and deep learning-based reconstructions.
Claims Coverage
The patent contains three independent claims covering a method, a controller, and a non-transitory computer-readable medium for driving an MRI system with specific inventive features.
Modification of first sampling diagram in repetitions
Performing accelerated echoplanar imaging with undersampling, wherein the pulse sequence diagram has repetitions each with a first sampling diagram for Nyquist ghost correction or magnetic field map generation, a second sampling diagram for accelerated echoplanar acquisition, and a common excitation diagram; and a real subset of repetitions has a modified first sampling diagram such that missing k-space data due to undersampling are supplemented and/or artifacts in image space are corrected based on acquired data.
Maintaining repetition duration during modification
In modifying the first sampling diagram, the duration of affected repetitions is maintained unchanged, preserving steady-state conditions without changing echo or repetition times.
Complete sampling of partial k-space region
The modified first sampling diagram and the quantity of repetitions in the real subset are chosen to achieve complete sampling of a partial k-space region necessary for complete supplementation of missing k-space data.
Phase and slice encoding in modified sampling
The modified first sampling diagram includes sampling of k-space lines in the readout direction with different phase encoding and at least partially different slice encoding.
Use of same type sampling diagrams for reference and accelerated acquisition
The same type of sampling diagram is used for both the modified first sampling diagram (reference data) and the second sampling diagram (accelerated echoplanar acquisition) to reduce artifacts and geometric distortions.
Temporal updating of reference data
Updating of the k-space data acquired with the modified first sampling diagram is performed at different times during the accelerated echoplanar imaging to adapt to dynamic changes and maintain image quality.
Specific gradient structure in modified first sampling diagram
The modified first sampling diagram comprises at least four successive phase encoding gradients and at least three successive readout gradients with alternating polarity interleaved in time with the phase encoding gradients.
Support for multiple accelerated imaging techniques
The method supports accelerated echoplanar imaging techniques including GRAPPA, SMS / Slice GRAPPA, SENSE, combined GRAPPA and SMS, and imaging techniques with dual polarity.
Synchronous switching of slice selection gradients
Slice selection gradients are switched synchronously with specific phase encoding gradients (second through fourth) in the modified first sampling diagram.
Phase encoding gradient amplitudes based on undersampling factor
Amplitudes of phase encoding gradients in the modified first sampling diagram are chosen based on the undersampling factor of the accelerated echoplanar acquisition such that skipped lines correspond to the undersampling factor minus one.
The independent claims collectively cover a method, controller, and computer-readable medium implementing a pulse sequence for accelerated echoplanar imaging with undersampling, wherein a subset of repetitions features a modified first sampling diagram for acquiring reference data that enable supplementation of missing k-space data and artifact correction without extending repetition duration, supporting multiple accelerated imaging techniques and optimized gradient switching strategies.
Stated Advantages
Reduction of total imaging acquisition time by integrating acquisition of reference data into the imaging pulse sequence, eliminating the need for separate calibration scans.
Preservation of spin steady state by maintaining repetition and echo times during modified acquisition segments, avoiding image artifacts caused by relaxation perturbations.
Improved image quality through enhanced correction of artifacts arising from undersampling, enabled by acquiring additional k-space reference data within the sequence.
Adaptability to dynamic changes such as patient movement or magnetic field variations by updating reference data during the scan, maintaining consistent image quality.
Compatibility with multiple accelerated imaging techniques including GRAPPA, SMS, dual polarity imaging, and deep learning reconstruction methods requiring coil sensitivity maps.
Documented Applications
Magnetic resonance imaging of examination subjects requiring accelerated echoplanar imaging with undersampled k-space data acquisition.
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