MRI Sub-Block Reacquisition for Motion Artifact Reduction
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Solution Overview
Problem
Magnetic resonance imaging systems face limitations in detecting and correcting fast movements due to latency and restricted field of view, leading to incomplete motion artifact correction in acquired image data sets.
Innovation Solution
A method for acquiring magnetic resonance data sets that involves repeating specific sub-blocks of the scan sequence based on motion information, where sub-blocks with excessive motion are re-acquired to minimize motion artifacts, using a threshold value to determine the need for re-acquisition and focusing on selective re-acquisition of echo signals or k-space lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motion correction methods (navigator acquisitions, field sampling, optical systems) are used to detect and correct patient motion in real time, then motion artifacts are reduced, but fast movements cannot be completely detected and corrected due to latency between motion detection and correction commands
Solution Approach 1:
The patent applies preliminary action by repeating sub-blocks proactively based on motion information detected during their execution. Motion information is evaluated in real-time during sub-block execution, and if motion exceeds a threshold, the sub-block is automatically repeated before the scan sequence completes, preventing motion artifacts rather than correcting them afterward
Solution Approach 2:
The patent implements feedback by continuously monitoring motion information during sub-block execution and using this information to control whether sub-blocks are repeated. The motion information feeds back to the control facility, which automatically decides on re-acquisition, creating a closed-loop system that responds to actual patient motion
2Device complexity
If the field of view of optical motion correction camera is reduced due to coil elements and head coil tiltability, then the system structure is maintained, but the angular range of head rotation that can be corrected is limited
Solution Approach 1:
The patent applies self-service by using the magnetic resonance system's own gradient coils and RF pulses to generate navigator echoes for motion detection. This eliminates the need for external optical cameras and their field of view limitations, allowing motion detection across the entire imaging volume without being constrained by coil structure or head position
3Device complexity
If navigator-based correction methods are used, then motion detection is simplified, but the scan frequency is much lower and latency is higher, reducing correction effectiveness
Solution Approach 1:
The patent implements continuity of useful action by acquiring motion information continuously during sub-block execution using navigator echoes or field sampling. This continuous acquisition maintains high scan frequency for motion detection, eliminating the low scan frequency and high latency problems of traditional navigator-based methods while keeping the approach simple
4Manufacturing precision
If sub-blocks are repeated selectively based on motion information, then image quality is improved by reducing motion artifacts, but additional scan time is required for re-acquisition
Solution Approach 1:
The patent applies partial action by selectively repeating only those sub-blocks where motion information indicates excessive motion. Instead of repeating the entire scan sequence or all sub-blocks, the system identifies and re-acquires only the specific portions affected by motion, improving image quality while minimizing additional scan time
Data Source
AI summary
A method for acquiring a magnetic resonance data set of an object under examination by a magnetic resonance system using a scan sequence is provided. The scan sequence includes a succession of sequence blocks, and in each sequence block, there is at least one sub-block including an excitation section and/or a detection section. An excitation section includes at least one excitation pulse, and in a detection section, an echo signal or an echo train is acquired as a scan signal. At least one item of motion information is provided for each sub-block. The motion information contains information about a movement of the object under examination within a duration of the sub-block. Some of the sub-blocks are automatically repeated. At least the sub-blocks having motion information that exceeds a threshold value are repeated. The threshold value defines a motion amplitude.