Multi-shot MRI Sequence for Diffusion and T2 Imaging
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Solution Overview
Problem
Current diffusion-weighted magnetic resonance imaging methods, particularly multi-shot techniques, face challenges in reducing total measurement times and efficiently generating T2-weighted or T2*-weighted images due to the need for optimal echo times and movement artifact correction.
Innovation Solution
The method involves acquiring diffusion-coded raw data through multiple partial diffusion gradient sequences with diffusion coding gradient pulses, followed by echo signals in a first and second echo time, and additional reference data without diffusion coding, allowing for the omission of navigator echoes and enabling the generation of higher-resolution reference images to reduce overall measurement time and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-shot measurement sequences are used to improve image quality and reduce artifacts, then image quality is improved, but measurement time increases due to multiple partial segments
Solution Approach 1:
The patent applies segmentation by dividing k-space into multiple partial segments that are acquired in succession across different shots. Each shot captures a specific portion of k-space, and these segments are later combined to form the complete image. This segmentation approach allows for improved image quality through multiple measurements while managing the trade-off with measurement time by efficiently organizing the acquisition process.
Solution Approach 2:
The patent implements preliminary action through navigator echoes that are acquired before the actual diffusion-weighted imaging data. These navigator echoes perform preliminary measurements of patient movement and phase variations, which are then used to correct the subsequent imaging data. This preliminary correction reduces movement artifacts and improves image quality without requiring a complete re-acquisition.
2Reliability
If navigator correction is implemented to reduce movement artifacts in multi-shot methods, then movement artifacts are reduced, but measurement time increases due to additional navigator echo acquisitions
Solution Approach 1:
The patent applies self-service by using the acquired diffusion-weighted imaging data itself to generate the correction information needed for navigator echo correction. The phase variations and movement information are extracted from the imaging data, which then serves to correct itself. This self-correcting mechanism reduces the need for separate, time-consuming navigator echo acquisitions while still achieving effective movement artifact reduction.
3Measurement precision
If optimal echo times are used for diffusion-weighted imaging to maximize signal quality, then signal-to-noise ratio is improved, but the ability to generate T2-weighted images is compromised
Solution Approach 1:
The patent implements universality by designing a pulse sequence that can generate multiple types of images (diffusion-weighted, T2-weighted, and T2*-weighted) from a single multi-echo acquisition. The same sequence, with optimal echo times for diffusion weighting, acquires data at multiple echo times, allowing reconstruction of different image types from the same dataset. This multi-functional approach eliminates the need for separate T2-weighted imaging sequences.
Solution Approach 2:
The patent applies parameter changes by varying the echo time parameter within the pulse sequence to generate different image contrasts. By acquiring data at multiple echo times (including optimal times for diffusion weighting and longer times for T2 weighting), the system can reconstruct images with different weighting characteristics from the same acquisition, effectively changing the contrast parameters post-acquisition.
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 total measurement times while maintaining or improving image quality, enabling the generation of diffusion-weighted, T2-weighted, and T2*-weighted images with reduced movement artifacts and increased diagnostic significance.
Implementation Method 1
a magnetic resonance apparatus controlled in accordance with such a method
Implementation Method 2
after a typical flipping of the relevant nuclear spins in one plane perpendicular to the basic magnetic field of the magnetic resonance scanner, a gradient magnetic field that varies the field strength of the external magnetic field
Implementation Method 3
Diffusion-weighted magnetic resonance exposures are magnetic resonance exposures with which the diffusion movement of specific substances (in particular water molecules) can be measured (detected) in the tissue of the body
Implementation Method 4
The precessing nuclei thereby go out of phase, which is noticeable in the measurement signal
Implementation Method 5
after a defined first echo time, raw data of a k-space region (k-space segment) are acquired during a first echo during each partial diffusion gradient sequence
Implementation Method 6
T2*-weighted exposures are likewise frequently additionally produced since these have a higher sensitivity with regard to hemorrhages
Data Source
AI summary
In a method described for generating magnetic resonance exposures in which diffusion-coded raw data are acquired with of a diffusion gradient measurement sequence having a number of partial diffusion gradient sequences, at least one diffusion coding gradient pulse is emitted in each partial data set, and raw data of a k-space region are acquired during a first echo after a defined first echo time the k-space regions in total covering a complete k-space. Raw data of an established navigator k-space region are acquired during a second echo after a second echo time the navigator k-space region being identical for different partial diffusion gradient sequences. Reference raw data are acquired by a reference measurement sequence with multiple partial reference sequences.