MRI Hyperpolarization Signal Navigator Echo Movement Correction
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) apparatuses face challenges in maintaining the reliability of hyperpolarization signals due to rapid attenuation and positional displacement caused by subject movements, which degrades the accuracy of metabolism information obtained from hyperpolarized nuclides.
Innovation Solution
The MRI apparatus employs a sequence controlling circuitry to obtain a navigator echo from a non-hyperpolarized nuclide, ensuring that the sums of gradient magnetic field applications during excitation and signal acquisition are minimized, thereby reducing signal loss and allowing for precise body movement correction without spoiling the hyperpolarized nuclide's spin state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gradient magnetic fields are applied for excitation and signal acquisition, then signal obtainment is enabled, but signal attenuation increases and hyperpolarized state is spoiled
Solution Approach 1:
The patent applies preliminary action by obtaining the navigator echo from the non-hyperpolarized nuclide before obtaining the hyperpolarization signal from the hyperpolarized nuclide. This allows movement information to be captured in advance without exposing the hyperpolarized state to gradient magnetic fields that would cause attenuation and spoil the signal.
Solution Approach 2:
The patent uses an intermediary approach by utilizing a non-hyperpolarized nuclide (such as protons) to obtain navigator echoes that carry movement information. This intermediary signal can be acquired with gradient magnetic fields without affecting the hyperpolarized nuclide, as the gradient effects are minimized (sum close to zero) and the timing is separated.
2Ease of operation
If gradient magnetic fields are applied during nuclide excitation, then excitation is achieved, but body movement correction reliability degrades due to signal loss
Solution Approach 1:
The navigator echo is obtained in advance before the hyperpolarization signal acquisition, allowing body movement information to be captured when the hyperpolarized nuclide is still in its stable hyperpolarized state, not exposed to gradient magnetic fields that would cause attenuation.
Solution Approach 2:
A non-hhyperpolarized nuclide serves as an intermediary to obtain movement information. The navigator echo from this intermediary nuclide reflects body movement without being affected by gradient-induced attenuation, providing reliable movement data for correction.
3Loss of information
If hyperpolarization signal is obtained, then metabolism information is enhanced, but positional displacement from subject movement degrades information reliability
Solution Approach 1:
Body movement information is obtained in advance via navigator echo before the hyperpolarization signal acquisition. This preliminary capture of movement data allows for accurate positional correction to be applied to the metabolism information, preventing degradation from positional displacement.
Solution Approach 2:
The navigator echo provides feedback information about body movement position and displacement. This feedback is used to correct the hyperpolarization signal data, compensating for positional changes due to subject movement and maintaining measurement precision.
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 enhances the reliability and precision of metabolism information in hyperpolarization images by minimizing signal attenuation and improving body movement correction, while maintaining the hyperpolarization signal's integrity.
Implementation Method 1
obtain a second magnetic resonance signal (a navigator echo) from a second nuclide (other than the first nuclide) in a non-hhyperpolarized state by exciting the second nuclide
Data Source
AI summary
A magnetic resonance imaging apparatus includes sequence controlling circuitry configured: to obtain, during a time period after excitation of a first nuclide in a hyperpolarized state but no later than before obtainment of a first magnetic resonance signal from the first nuclide, a second magnetic resonance signal from a second nuclide that is different from the first nuclide and is in a non-hyperpolarized state, by exciting the second nuclide; and to control each of gradient magnetic field waveforms so as to cause both a first sum indicating a sum of application amounts of a gradient magnetic field related to the excitation of the second nuclide and a second sum indicating a sum of application amounts of a gradient magnetic field related to the obtainment of the second magnetic resonance signal to be close to zero, no later than before the obtainment of the first magnetic resonance signal.