Stimulated-Echo EPRI Imaging With High-Isolation RF Coils
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Solution Overview
Problem
Existing electron paramagnetic resonance imaging (EPRI) methods struggle to provide non-invasive, high signal-to-noise ratio (SNR) images of internal structures and processes in the human body, particularly distinguishing malignant tissue from healthy tissue, due to confounding factors in T2 relaxation measurements.
Innovation Solution
Employing high-isolation transmit/receive surface coils and a series of phase-shifted and temporally spaced RF pulses, combined with T1-sensitive inversion-recovery imaging, to measure T1 relaxation and enhance SNR for improved micro-environmental imaging, allowing distinction between different tissue types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If T2 relaxation measurements are used for imaging, then imaging capability is provided, but signal-to-noise ratio is reduced due to confounding factors
Solution Approach 1:
The patent changes the measurement parameter from T2 relaxation time to T1 relaxation time. By using inversion-recovery imaging sequences that specifically measure T1, the method avoids confounding factors present in T2 measurements while maintaining imaging capability. This parameter substitution resolves the contradiction by finding an alternative measurement approach that achieves both high SNR and reliable tissue differentiation.
2Measurement precision
If high-isolation transmit/receive surface coils are used, then signal reception is improved, but device complexity increases
Solution Approach 1:
The patent introduces high-isolation transmit/receive surface coils as an intermediary component between the RF transmission system and the signal detection system. These specialized coils with high isolation properties act as a mediator that prevents transmitted RF pulses from being received by the same coils, thereby improving SNR. The complexity is accepted as a necessary trade-off to achieve the desired measurement precision.
3Measurement precision
If phase-shifted and temporally spaced RF pulses are employed, then T1 relaxation measurement is enhanced, but measurement time increases
Solution Approach 1:
The patent employs periodic RF pulse sequences with specific temporal spacing and phase shifts to efficiently measure T1 relaxation. By using repeated inversion-recovery cycles with optimized timing, the method achieves accurate T1 measurements while minimizing total acquisition time. The periodic application of pulses at carefully selected intervals allows for rapid sampling of the relaxation curve.
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
The method provides enhanced SNR for imaging, enabling spatially and temporally resolved images of tissue/cell protein signals, particularly under hypoxic conditions, and effectively differentiates malignant from healthy tissue.
Implementation Method 1
transmitted radio frequency (RF) energy that disturbs the electron-spin alignment, and then receive the much-weaker resulting RF signal as the electron spins realign to the static magnetic field
Implementation Method 2
electron paramagnetic resonance imaging (EPRI)
Implementation Method 3
high-isolation transmit/receive surface, volume, or surface-volume coils that are configured to reduce the reception of the transmitted RF pulses by the receive coils
Implementation Method 4
T1-sensitive inversion-recovery imaging, to measure T1 relaxation and enhance SNR
Implementation Method 5
The T1 spin echo is temporally separated from the third excitation pulse enough to allow better sensing (better signal-to-noise ratio (SNR))
Data Source
AI summary
An apparatus and method for improved S/N measurements useful for electron paramagnetic resonance imaging in situ and in vivo, using high-isolation transmit/receive surface coils and temporally spaced pulses of RF energy (e.g., in some embodiments, a RF pi pulse) having an amplitude sufficient to rotate the magnetization by 180 degrees followed after varied delays, by a second RF pulse having an amplitude half that of the initial pulse to rotate the magnetization by, e.g., 90 degrees (a pi/2 pulse), to the plane orthogonal to the static field where it evolves for a short time. Then a third RF pi pulse sufficient to rotate the magnetization by, e.g., 180 degrees, forms an echo (in some embodiments, the second and third pulses are from the same signal as the first pulse but are phase shifted by 0, 90, 180, or 270 degrees to reduce signal artifact), to image human body.