MRI Multi-Slice Acquisition via Coherent Refocusing Gradients
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Solution Overview
Problem
Conventional MRI techniques are time-consuming and result in blurry images when attempting to simultaneously acquire multi-slice or multi-slab images, limiting the thickness of slices and degrading image quality if blur exceeds 3 pixels.
Innovation Solution
The method involves applying at least one coherent refocusing gradient between separation gradients, along with RF pulses carrying multiple frequency components and spatial encoding gradients, to simultaneously excite and separate multiple slices or slabs without additional hardware or computational resources, allowing for efficient reconstruction of clear images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple slices are acquired sequentially using conventional 2D spatial encoding, then image quality is maintained, but the acquisition time increases significantly
Solution Approach 1:
The patent combines multiple slice excitations into a single scan by applying an RF pulse with multiple frequency components simultaneously. Each frequency component corresponds to a different slice, allowing multiple slices to be excited and acquired in parallel within one TR period, thereby reducing total acquisition time while maintaining image quality through the coherent refocusing gradient
Solution Approach 2:
The patent employs periodic separation gradients applied between coherent refocusing gradients to periodically refocus spins from different slices at different times. This periodic action allows multiple slices to be acquired within a single TR period by timing the refocusing events to occur at different phases of the RF echo train, effectively parallelizing the acquisition process
2Loss of time
If slice thickness is increased to reduce scan time, then acquisition time decreases, but image blur increases beyond acceptable levels
Solution Approach 1:
The patent applies coherent refocusing gradients between separation gradients as a preliminary action to refocus spins before they become significantly dephased. This preliminary refocusing maintains signal coherence and image sharpness even when using thicker slices, allowing the system to use larger slice thickness without exceeding the 3-pixel blur threshold while still achieving faster acquisition
3Productivity
If 3D spatial encoding is used to acquire multiple slices in one scan, then acquisition time is reduced, but the number of phase encodings increases leading to longer scan times
Solution Approach 1:
The patent segments the 3D acquisition space into multiple 2D slices that can be independently excited and encoded. By applying separation gradients between coherent refocusing gradients, the system treats each slice as a separate 2D encoding problem rather than a single 3D volume, reducing the total number of phase encoding steps required while still acquiring multiple slices in one scan
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 significantly reduces the time required for acquiring multiple slices or slabs while maintaining or improving image clarity, enabling efficient and sharp MRI signal acquisition compatible with various existing MRI systems.
Implementation Method 1
A magnetic resonance imaging (MRI) apparatus is configured to reconstruct MR images based on MR signals. An MRI apparatus typically applies a static magnetic field, a gradient magnetic field, and a radio frequency (RF) signal having a selected frequency to a subject to excite a selected nucleus type
Implementation Method 2
applying one or more than one RF pulse, which carries at least two frequency components, and a slice/slab selection gradient to a subject, so that at least two slices/slabs of the subject respectively corresponding to the at least two frequency components can be excited simultaneously
Data Source
AI summary
A method for acquiring MRI signals includes: applying one or more than one RF pulse, which carries at least two frequency components, and a slice/slab selection gradient to a subject, so that at least two slices/slabs of the subject respectively corresponding to the at least two frequency components are excited simultaneously; applying a plurality of spatial encoding gradients; applying a plurality of separation gradients for separating the at least two slices/slabs; and applying at least one coherent refocusing gradient between the plurality of separation gradients.