MRI EPI Sampling Integration for Faster Nyquist Ghost Correction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) methods, particularly echoplanar imaging (EPI), are slow due to long acquisition times caused by spin relaxation, limiting patient comfort and requiring stationary positioning, and existing acceleration techniques increase measuring time with additional navigator data acquisitions.
Innovation Solution
A method for MRI that modifies the sampling diagram in EPI to undersample k-space data, using a modified first sampling diagram to acquire additional data for Nyquist ghosting correction and magnetic field mapping, integrating these acquisitions into the EPI process without separate navigator scans, and applying auto-calibration to reconstruct missing data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate navigator scans are performed for Nyquist ghosting correction and magnetic field mapping, then measurement precision is improved, but acquisition time increases
Solution Approach 1:
The patent combines the acquisition of navigator data for Nyquist ghosting correction and magnetic field mapping into a single integrated sampling process. The first sampling diagram simultaneously collects both types of correction data during the EPI sequence execution, eliminating the need for separate navigator scans and reducing total acquisition time while maintaining measurement precision.
Solution Approach 2:
The first sampling diagram is designed to serve multiple functions: it acquires k-space data for image reconstruction, collects navigator data for Nyquist ghosting correction, and obtains data for magnetic field mapping. This multi-functional approach allows a single sampling process to accomplish what previously required multiple separate acquisitions.
2Reliability
If separate navigator scans are performed for Nyquist ghosting correction and magnetic field mapping, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent merges the acquisition of navigator data for Nyquist ghosting correction and magnetic field mapping into a single integrated sampling process. The first sampling diagram simultaneously collects both types of correction data during the EPI sequence execution, eliminating the need for separate navigator scans and reducing total acquisition time while maintaining measurement precision.
Solution Approach 2:
The integrated sampling approach allows the MRI system to continuously acquire all necessary data (image k-space data, ghosting correction data, and field mapping data) in a single uninterrupted EPI sequence. This eliminates idle time between separate navigator scans and maintains continuous useful action throughout the acquisition process.
3Loss of time
If k-space data is undersampled to accelerate acquisition, then acquisition time is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies partial sampling (undersampling) of k-space data to accelerate the main image acquisition, while performing complete or enhanced sampling for the first sampling diagram that collects correction data. This selective approach allows the system to reduce overall acquisition time through undersampling while maintaining sufficient precision in the correction data needed to reconstruct the undersampled image.
Solution Approach 2:
The patent uses navigator data acquired through the first sampling diagram as an intermediary to correct artifacts and enable accurate reconstruction of the undersampled k-space data. This intermediary correction data acts as a mediator that allows the system to tolerate the precision loss from undersampling while still achieving high-quality images through subsequent correction processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces acquisition time by eliminating the need for separate navigator scans, maintaining spin steady state, and improving image quality through artifact correction, thus enhancing efficiency and patient comfort.
Implementation Method 1
Magnetic resonance imaging (MRI) methods, particularly echoplanar imaging (EPI), are slow due to long acquisition times caused by spin relaxation
Implementation Method 2
a rapidly switched magnetic field—what is known as the gradient field—for spatial resolution of the imaging signal
Implementation Method 3
The magnitude of the magnetization (in particular of the transverse magnetization in a plane transverse to the previously described basic magnetic field) at a specific location of the examination subject can be determined from the data of the readout point with the aid of a Fourier transformation
Data Source
AI summary
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.