Birdcage RF Coil Gradient Protrusion Homogeneity
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Solution Overview
Problem
Birdcage type RF coils face challenges in maintaining homogeneous sensitivity distribution along the z-axis direction when the rung length is shortened, limiting their use in higher magnetic field intensity MRI systems, and require complex adjustments and increased costs for larger coils.
Innovation Solution
A birdcage type RF coil configuration with a gradient coil that protrudes inward and an RF shield with varying diameters, allowing for a concave shape that increases magnetic field efficiency and reduces the rung length while maintaining homogeneous sensitivity, and the use of RF coil/RF shield connecting parts via capacitors to improve sensitivity distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rung length of a birdcage type RF coil is shortened, then the magnetic field generating efficiency is improved and the coil size is reduced, but the sensitivity distribution homogeneity along the z-axis direction deteriorates
Solution Approach 1:
The RF coil is divided into multiple independent resonant elements (rungs) that can be independently controlled. Each rung acts as an independent resonant circuit, allowing individual adjustment of current distribution to compensate for the shortened length and maintain homogeneous sensitivity across the imaging region.
Solution Approach 2:
The patent changes the electrical parameters (resonant frequency, Q-value, current distribution) of the RF coil by adjusting the capacitor values and driving frequencies of the multiple rungs. This allows optimization of the sensitivity distribution even with shorter rung lengths, resolving the contradiction between compact size and uniform sensitivity.
2Device complexity
If the number of electric power supply ports is reduced, then the device complexity and cost are reduced, but the adjustment flexibility and sensitivity optimization capability deteriorate
Solution Approach 1:
The patent makes the RF coil structure universal by designing it with multiple rungs that can serve dual purposes: as resonant elements for sensitivity optimization and as independent adjustable elements for tuning. This multi-functionality allows a single coil structure to handle various imaging requirements without needing multiple separate coils or complex adjustment mechanisms.
Solution Approach 2:
The patent introduces dynamic adjustability through independent capacitor control and frequency tuning of each rung. This dynamic capability allows the system to adapt to different imaging scenarios and optimize sensitivity distribution in real-time, compensating for the reduced number of fixed power supply ports through flexible electronic control.
3Area of stationary object
If larger RF coils are used for higher magnetic field intensity systems, then the sensitivity coverage is improved, but the Q values decrease and the coil size exceeds the wavelength
Solution Approach 1:
The patent segments the large RF coil into multiple smaller resonant elements (rungs) that operate independently. This segmentation allows the overall coil to cover a large area while each individual rung maintains a compact size that preserves high Q values, even when used in high magnetic field intensity systems.
Solution Approach 2:
The patent transitions from a single large planar coil to a three-dimensional structure with multiple rungs arranged in space. This spatial arrangement allows the coil to achieve large sensitivity coverage area while maintaining compact electrical dimensions for each resonant element, thereby preserving high Q values at high frequencies.
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
Enables a larger homogeneous sensitivity region along the axial direction with shortened rung lengths, improving magnetic field generating efficiency and reducing costs by simplifying adjustments and reducing the number of electric power supply ports, while maintaining sensitivity homogeneity.
Implementation Method 1
An MRI system irradiates electromagnetic waves on a subject stayed in a uniform static magnetic field generated by a magnet to excite nuclear spins in the subject
Implementation Method 2
receives nuclear magnetic resonance signals which are electromagnetic waves generated by the nuclear spins
Implementation Method 3
In the case of high pass RF coil, capacitors are disposed in the aforementioned rings. It is tuned by attaching electrical components such as capacitors and diodes to constitute an RF transmitting coil
Data Source
AI summary
A coil unit comprises a gradient coil which is disposed along a static magnetic field generating source, and a radio frequency coil which is disposed along the gradient coil in a test region at a position closer to the center of the test region compared with the gradient coil, and a conductor part which is disposed between the gradient coil and the radio frequency coil, and covers periphery of the radio frequency coil. The radio frequency coil comprises a first loop coil and a second loop coil locating in planes substantially perpendicular to direction of the static magnetic field, a plurality of linear conductors connecting the first loop coil and the second loop coil and substantially parallel to the direction of the static magnetic field, and a plurality of first capacitors disposed in the first loop coil and the second loop coil.