Split-Echo Split-Blade MRI Data Collection
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Solution Overview
Problem
Fast Spin Echo (FSE) magnetic resonance imaging faces challenges with non-CPMG artifacts due to phase discrepancies, particularly in diffusion weighted imaging, leading to rapid signal decay and inefficient data acquisition in PROPELLER techniques, which often result in narrow blade artifacts and prolonged scanning times.
Innovation Solution
A method and system for split-echo, split-blade data collection that splits each echo train into pairs within a single k-space, using gradient pulses to acquire non-parallel k-space blades, allowing for efficient data acquisition without reducing blade width and mitigating non-CPMG artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high flip angle refocusing RF pulses are used to stabilize echo train, then signal stability is improved, but scanning time is prolonged due to SAR limits
Solution Approach 1:
The echo train is segmented into multiple sub-echo trains, each with fewer refocusing pulses. This reduces the cumulative SAR per TR interval, allowing the use of higher flip angles within each sub-train to maintain signal stability without exceeding overall SAR limits, thereby reducing total scan time.
Solution Approach 2:
The pulse sequence employs periodic modulation of the refocusing RF pulse train, creating alternating high-and low-SAR intervals. During high-SAR intervals, higher flip angles are applied to stabilize echo train; during low-SAR intervals, the sequence recovers. This periodic structure maintains signal stability while adhering to average SAR constraints, reducing scanning time.
2Productivity
If standard FSE sequence is used, then data acquisition is efficient, but non-CPMG artifacts cause rapid signal decay
Solution Approach 1:
An intermediary phase-cycling scheme is introduced where the phase of refocusing RF pulses is systematically varied across different TR intervals. This phase cycling acts as a mediator that separates the desired signal from non-CPMG artifacts through coherent addition, maintaining signal stability without sacrificing data acquisition efficiency.
Solution Approach 2:
The pulse sequence dynamically changes the phase parameter of refocusing RF pulses according to a predetermined cycle pattern. By modulating this parameter, the sequence maintains CPMG condition compliance while efficiently acquiring data, preventing rapid signal decay from non-CPMG artifacts.
3Reliability
If PROPELLER technique with split-blade acquisition is used, then non-CPMG artifacts are mitigated, but blade width is reduced causing narrow-blade artifacts
Solution Approach 1:
The patent extends the conventional 2D k-space sampling into a 3D phase-encoding space by incorporating an additional phase-cycling dimension. This allows the reconstruction algorithm to differentiate between true signal and non-CPMG artifacts while maintaining full blade width, eliminating narrow-blade artifacts while preserving artifact mitigation.
4Loss of information
If diffusion weighting gradients are applied, then diffusion contrast is achieved, but phase variability increases causing signal loss
Solution Approach 1:
The pulse sequence incorporates a feedback mechanism where the phase accumulated during diffusion weighting is measured and compensated in subsequent TR intervals. This feedback loop maintains consistent phase relationships across echoes, preserving signal intensity while retaining diffusion contrast information.
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 stabilizes echo trains by generating consistent phases for each echo pair, reducing destructive interference and maintaining signal intensity, while maintaining data acquisition efficiency and avoiding narrow-blade artifacts, thus improving image quality and scanning time.
Implementation Method 1
Fast Spin Echo (FSE) magnetic resonance imaging
Implementation Method 2
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Data Source
AI summary
A computer readable storage medium has stored thereon a computer program having instructions, which, when executed by a computer, cause the computer to apply a first plurality of RF pulses during a first TR interval of an MR pulse sequence to generate a first echo train. A plurality of echoes of the first echo train are split into a plurality of echo pairs. Within a first echo space, first and second gradient pulses are applied during respective first and second generated echoes, and respective first and second sets of k-space data are acquired that correspond to respective first and second blades of k-space data in the same k-space. The first and second blades have orientations at different angles from one another. The instructions further cause the computer to reconstruct an image based on the acquired first and second sets of k-space data.