Nonlinear Magnetic Gradient Encoding for Fast MRI
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Solution Overview
Problem
Conventional Magnetic Resonance Imaging (MRI) techniques are slow, limiting throughput and increasing healthcare costs due to the need for long scan times, which is exacerbated by the inefficiency of linear magnetic gradients in data collection and image reconstruction.
Innovation Solution
The use of nonlinear magnetic gradient fields combined with parallel receiver technology, dynamically modulating these gradients to impose a unique phase/frequency time-varying signal on each pixel, allowing for spatial localization with a single echo acquisition, thereby reducing scan times and improving image reconstruction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional linear magnetic gradients are used for spatial encoding, then the MRI system can produce images with standard resolution, but the scan time becomes excessively long (on the order of 1 hour per patient)
Solution Approach 1:
The patent applies dynamic gradient modulation by varying the amplitude and timing of magnetic gradients during the echo train. The gradients are modulated at different frequencies and phases to encode spatial information dynamically across multiple echoes, enabling fast imaging while maintaining resolution. This dynamic approach allows the system to collect sufficient k-space data in a single echo train rather than requiring multiple repeated excitations.
Solution Approach 2:
The patent changes the parameters of the magnetic gradient fields, specifically using non-linear gradient waveforms with varying amplitudes and timing. By modifying the gradient strength, duration, and temporal profile, the system can encode spatial information more efficiently. The gradient parameters are optimized to achieve both fast data acquisition and adequate spatial encoding within the constraints of a single echo train.
2Productivity
If multiple repetition times (TRs) are used to gather sufficient k-space information, then image quality can be maintained, but the throughput and availability of MRI decreases
Solution Approach 1:
The patent implements continuous data acquisition throughout the echo train by continuously sampling the MR signal while the gradients are being applied. This continuous sampling allows the system to collect all necessary k-space information in a single uninterrupted echo train, eliminating the need for multiple discrete TR cycles. The useful action of data collection continues without interruption, maximizing throughput while maintaining image quality.
3Loss of time
If linear magnetic gradients create plane-wave oscillations for Fourier encoding, then the k-space data can be reconstructed via FFT, but the information gathering efficiency is reduced resulting in longer scan times
Solution Approach 1:
The patent employs non-linear gradient waveforms that create curved or oscillating gradient paths rather than simple linear ramps. These curved gradient trajectories encode spatial information more efficiently by creating more varied phase evolution patterns across the echo train. The non-linear gradients generate richer phase information that can be decoded more efficiently, improving information gathering efficiency and reducing scan time.
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 enables fast imaging by efficiently encoding signals, allowing for complete image reconstruction in minimal time, such as 4 ms, while maintaining image quality and reducing noise artifacts, thus addressing the limitations of conventional MRI techniques.
Implementation Method 1
Magnetic Resonance Imaging (MRI) is a medical imaging technique based on the phenomenon of nuclear magnetic resonance (NMR)
Implementation Method 2
If the frequency of the RF pulse matches the Larmor frequency of protons in the volume, the pulse may induce a spin-flip transition of the protons
Implementation Method 3
Magnetic Resonance Imaging (MRI) is a medical imaging technique based on the phenomenon of nuclear magnetic resonance (NMR)
Implementation Method 4
When the protons relax after the pulse, they will then emit RF signals at the Larmor frequency which can be detected with receiver coils
Data Source
AI summary
Efficient encoding of signals in an MRI image is achieved through a combination of parallel receiver coils, and nonlinear gradient encoding that varies dynamically in such a manner as to impose a unique phase/frequency time varying signal on each pixel in the field of view. Any redundancies are designed such that they are easily resolved by the receiver coil sensitivity profiles. Since each voxel has an essentially identifiable complex temporal signal, spatial localization is easily achieved with only a single echo acquisition.