Dynamic B0 Field Map Correction for MRI Distortion
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Solution Overview
Problem
Dynamic image correction in magnetic resonance imaging (MRI) is challenged by geometric distortions caused by external influences like breathing, which existing methods struggle to accurately address without significantly increasing recording time or introducing inaccuracies.
Innovation Solution
A method that combines a reliable B0 field map from a pre-scan with dynamically obtained field maps during continuous recordings, using a comparison to identify and correct distortions, allowing for real-time adjustment of image data without additional time expenditure, utilizing a control sequence-generating computer and field map correction computer to process and correct distorted data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic field map updates are performed during continuous EPI recording using the PLACE method, then correction accuracy for breathing movements is improved, but inaccuracies occur due to phase differences between repeated slice recordings
Solution Approach 1:
A reference field map acquired from a gradient echo recording is introduced as an intermediary to mediate between the dynamically updated field maps. This reference field map serves as a stable baseline that eliminates the phase difference problem inherent in PLACE method, allowing accurate distortion correction without the reliability issues of dynamic field map updates
2Reliability
If gradient echo recordings are used to acquire undistorted B0 field maps, then field map accuracy is improved, but recording time is significantly increased making them unsuitable for continuous image recording
Solution Approach 1:
The gradient echo recording for the reference field map is performed as a preliminary action before the continuous EPI recording. This allows the time-consuming accurate field map acquisition to be done once in advance, while the subsequent continuous imaging can proceed rapidly without time loss
3Measurement precision
If repeated slice recordings are performed to create updated field maps during continuous recording, then dynamic distortion correction is improved, but image quality deteriorates due to phase differences from patient movement
Solution Approach 1:
The reference field map acts as an intermediary that decouples the distortion correction process from the continuous image acquisition. By using this pre-acquired reference, the system achieves dynamic distortion correction without performing repeated slice recordings that would introduce phase differences and degrade image quality
Data Source
AI summary
In a method and apparatus for the correction of image data dynamically acquired with a magnetic resonance imaging method, a reliable B0 field map is recorded as a basic reference field map. Image data (VB) with distorted coordinates are also acquired over a predefined recording time. In addition, a set of distorted, dynamically obtained B0 field maps is acquired during the recording time. Incorrect B0 field maps are identified by comparison of the dynamically obtained B0 field maps with the basic reference field map, and the set of distorted, dynamically obtained B0 field maps is corrected accordingly. The acquired image data with distorted coordinates are corrected with the use of the corrected set of distorted, dynamically obtained B0 field maps.