Split-Blade PROPELLER MRI Acquisition with Quadratic Phase Modulation
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Solution Overview
Problem
Conventional diffusion-weighted FSE imaging techniques face challenges such as high phase sensitivity to motion, signal degradation due to non-compliance with the Carr-Purcell-Meiboom-Gill condition, and elongated acquisition times in PROPELLER imaging, which are exacerbated by high specific absorption rate and sensitivity to dielectric effects.
Innovation Solution
Implementing a split-blade data collection method for PROPELLER MRI in combination with a quadratic phase modulation scheme, where odd and even echoes are stored in perpendicular blades in k-space, allowing for reduced scan time and correction of phase and magnitude differences using overlapping regions, thereby eliminating the need for double encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quadratic phase modulation scheme (LRX) is used in diffusion-weighted FSE imaging, then signal magnitude and phase are sustained regardless of initial signal phase, but the echo train must be twice as long due to double encoding of odd and even echoes, leading to elongated acquisition time
Solution Approach 1:
The patent segments the echo train into separate odd and even echo acquisitions, each filling different portions of k-space. Instead of acquiring both odd and even echoes at every TR interval (double encoding), the method alternates between odd and even echo acquisitions across successive TR intervals, effectively halving the echo train length required while maintaining complete k-space coverage.
Solution Approach 2:
The patent introduces a temporal dimension to the encoding scheme by alternating between odd and even echo acquisitions across successive TR intervals. This temporal alternation allows the system to fill different k-space regions at different times, eliminating the need for simultaneous double encoding and reducing the echo train length.
2Loss of time
If conventional diffusion-weighted FSE imaging is performed, then acquisition time is reduced compared to LRX modulation, but the signal is substantially degraded due to violation of the CPMG condition
Solution Approach 1:
The patent changes the phase modulation parameters of the refocusing RF pulses according to a quadratic phase modulation scheme. Specifically, the phase of refocusing pulses is modulated as a function of echo number, which corrects the phase accumulation errors that occur when the CPMG condition is violated, thereby maintaining signal quality while using shorter echo trains.
3Reliability
If PROPELLER imaging with LRX modulation is used, then signal sustainability is improved, but the echo train length must be doubled due to double encoding, resulting in increased scan time
Solution Approach 1:
The patent segments k-space acquisition into separate odd and even echo blades acquired at alternating TR intervals. This segmentation eliminates the need for double encoding within a single echo train, reducing the effective echo train length while maintaining complete k-space coverage through the alternating acquisition pattern.
Solution Approach 2:
The patent maintains continuous useful action by alternating between odd and even echo acquisitions across successive TR intervals. This continuous alternation ensures that k-space is filled efficiently without idle periods, maintaining scan productivity while using shorter echo trains.
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 scan time, minimizes image artifacts like dielectric artifacts and background streaking, and maintains or improves image quality by correcting phase and magnitude differences, making diffusion-weighted imaging more efficient and robust.
Implementation Method 1
magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 2
the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency
Implementation Method 3
tissues that have either higher or lower water self-diffusion characteristics
Data Source
AI summary
An apparatus and method of MR imaging is disclosed. The apparatus and method comprises segmenting acquisition of an echo train into separate odd and even acquisition blades in k-space, wherein the odd and even acquisition blades extend orthogonally through a common reference point in a central region of k-space. A segment of MR data is acquired using a quadratic phase modulation scheme, wherein a first set of MR echo signals occurring after odd-numbered RF refocusing pulses are stored in the odd acquisition blade, and a second set of MR echo signals occurring after even-numbered RF refocusing pulses are stored in the even acquisition blade. This acquisition and segmentation is repeated until a sufficient number of blades are acquired to fill k-space. Finally, an image is reconstructed from the acquisition blades.