MRI Receive Coil Inductive Path for B1-Field Uniformity
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Solution Overview
Problem
Single loop MR coils used in high magnetic fields of 3 T and above suffer from receive |B1|-field distortion, leading to a reduced MRI signal-to-noise ratio (SNR).
Innovation Solution
A conducting loop with a detuning trace and a receive |B1|-field uniformity-enhancing inductor positioned parallel to the B0 magnetic field is used to optimize |B1|-field uniformity, supplemented by end inductors for detuning during the transmit phase and calibration to enhance receive |B1|-field uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single loop is used in B0 magnetic fields of 3 T and above, then the coil structure is simple, but receive |B1|-field distortion occurs resulting in reduced SNR
Solution Approach 1:
The conducting loop is divided into multiple segments by introducing a conducting trace with inductors that creates multiple current paths. This segmentation allows different portions of the loop to contribute differently to the B1-field, enabling correction of field distortion while maintaining a relatively simple overall structure.
Solution Approach 2:
Inductors are strategically positioned at specific locations along the conducting trace to create localized magnetic field corrections. The inductors at different positions have different values, providing locally optimized field uniformity enhancement at critical regions of the imaging volume.
2Measurement precision
If a conducting trace with inductors is added to the loop, then receive |B1|-field uniformity is enhanced, but device complexity increases
Solution Approach 1:
The conducting trace with inductors is merged with the existing loop structure, sharing common conductive paths and support structures. This integration approach allows the field uniformity enhancement functionality to be added while minimizing the increase in overall device complexity.
Solution Approach 2:
The conducting trace serves multiple functions: it provides the inductive path for B1-field uniformity enhancement, acts as a detuning mechanism during transmit phases, and can be integrated with the loop's structural support. This multi-functionality reduces the need for separate components, thereby limiting complexity increase.
3Reliability
If the conducting loop is detuned from Larmor frequency during transmit, then coil protection is achieved, but receive sensitivity may be affected
Solution Approach 1:
The coil's resonant frequency is dynamically adjusted using the conducting trace and inductors to create a frequency-selective response. During transmit phases, the coil is detuned to protect against high power; during receive phases, it is tuned to the Larmor frequency to maximize sensitivity. This dynamic frequency control allows the coil to optimize performance for each operational mode.
Solution Approach 2:
The coil alternates between detuned and tuned states in periodic correspondence with the MRI sequence timing. The conducting trace enables rapid frequency switching that synchronizes with the transmit-receive cycles, ensuring protection during high-power transmit while maintaining full sensitivity during receive windows.
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 solution reduces receive |B1|-field distortion and enhances SNR by optimizing |B1|-field uniformity, improving the performance of MR scanners.
Implementation Method 1
a conducting loop that is resonant at a Larmor frequency of a design-basis B0 magnetic field of at least 3 Tesla
Implementation Method 2
Larmor frequency of a design-basis B0 magnetic field
Implementation Method 3
a conducting trace configured to detune the conducting loop from the Larmor frequency in response to a DC current flowing through the conducting trace
Implementation Method 4
a receive |B1|-field uniformity-enhancing inductor positioned at an intermediate point along the conducting trace
Implementation Method 5
receive |B1|-field uniformity-enhancing inductor positioned on a portion of the conductive trace oriented parallel with the design-basis Bo magnetic field
Data Source
AI summary
A magnetic resonance (MR) receive coil (18) includes a conducting loop (20) that is resonant at a Larmor frequency of a design-basis B0 magnetic field of at least 3 Tesla; and a conducting trace (22) configured to detune the conducting loop from the Larmor frequency in response to a DC current flowing through the conducting trace. The conducting trace further includes a receive |B1|-field uniformity-enhancing inductor (L3) positioned at an intermediate point along the conducting trace.