MRI Birdcage Coil Distributed RF Amplification
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Solution Overview
Problem
Conventional magnetic resonance radio frequency transmission devices for birdcage coils require bulky, expensive, and heavy radio frequency amplifiers and circulators, leading to a trade-off between cost, weight, and power loss, and are not flexible in generating radio frequency excitation fields, especially for high-field strength applications.
Innovation Solution
A magnetic resonance radio frequency transmission device with a birdcage coil that includes a pair of conductive loop members and conductive segments interconnected by activation ports, utilizing multiple radio frequency amplifier units that provide adjustable power and phase settings, allowing for operation at multiple resonance frequencies and reducing the need for bulky components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional high-power radio frequency amplifiers and circulators are used to generate radio frequency excitation fields for birdcage coils, then the required power and field strength are achieved, but the device becomes bulky, expensive, and heavy
Solution Approach 1:
The invention divides the single high-power radio frequency source into multiple lower-power radio frequency amplifier units (e.g., 4 units instead of 1), where each unit provides power to a specific activation port on the birdcage coil. This segmentation allows the system to achieve the required total power while using smaller, lighter amplifier units that can be strategically positioned near the coil rather than requiring one large centralized power source
Solution Approach 2:
The invention transitions from a centralized power delivery architecture to a distributed multi-port architecture. By adding the spatial dimension of multiple activation ports around the birdcage coil and multiple amplifier units positioned at different locations, the system achieves power delivery without requiring long power cables and bulky centralized components
2Power
If conventional radio frequency transmission devices use long power cables and circulators, then power delivery is achieved, but power loss increases and device complexity increases
Solution Approach 1:
The radio frequency amplifier units are positioned in close proximity to the birdcage coil activation ports before power delivery occurs. This preliminary positioning eliminates the need for long power cables that would otherwise transmit power over extended distances, thereby minimizing resistive power losses in the transmission path
Solution Approach 2:
The invention extracts and eliminates the circulator component from the conventional radio frequency transmission architecture. By using multiple independent amplifier units directly connected to activation ports, the system achieves power delivery and impedance matching without requiring circulators, thereby reducing both device complexity and associated power losses
3Device complexity
If conventional birdcage coils use fixed excitation modes, then simple hardware configuration is maintained, but flexibility in generating radio frequency excitation fields is limited
Solution Approach 1:
The invention introduces dynamic controllability to the birdcage coil system by enabling independent amplitude and phase adjustment of each radio frequency amplifier unit. This allows the system to dynamically switch between different excitation modes (quadrature mode, dual radio frequency channel modes, etc.) and adapt to different application requirements without changing the physical hardware configuration
Solution Approach 2:
The multiple activation ports and independently controllable amplifier units create a universal platform that can perform multiple functions: quadrature excitation, dual radio frequency channel operation, radio frequency shimming, and operation at multiple resonance frequencies. This multi-functionality is achieved within the same hardware architecture, enhancing versatility without proportionally increasing complexity
4Adaptability or versatility
If birdcage coils operate at multiple resonance frequencies with distributed excitation, then flexibility and field homogeneity are improved, but the number of activation ports and amplifier units increases
Solution Approach 1:
The invention applies local quality by positioning each radio frequency amplifier unit in close proximity to its corresponding activation port on the birdcage coil. This local arrangement allows the system to utilize multiple activation ports and amplifier units for operation at multiple resonance frequencies and different excitation modes, while minimizing the overall complexity by eliminating the need for long interconnections and centralized power distribution infrastructure
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 configuration reduces the requirement for high-power radio frequency components, eliminates the need for circulators and long power cables, and enables flexible operation in quadrature mode or dual radio frequency channel modes, optimizing the homogeneity of the radio frequency excitation field while minimizing hardware complexity.
Implementation Method 1
the birdcage resonator, also known as birdcage coil, is a well-known volume radio frequency coil design for generating a radio frequency magnetic excitation field B1 to be applied to nuclei of or within a subject of interest
Implementation Method 2
They are usually operated in resonance at a radio frequency corresponding to the Larmor frequency, which depends on the strength of the static magnetic field B0 in the gyromagnetic magnetic ratio of the species of nuclei under consideration
Implementation Method 3
a static, homogeneous magnetic field B0 arranged substantially perpendicular to the radio frequency magnetic excitation field B1
Data Source
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AI summary
A magnetic resonance radio frequency transmission device (140) for generating and applying a radio frequency excitation field B1 for the purpose of magnetic resonance examination comprises a birdcage coil (144) and a plurality of M radio frequency amplifier units for providing radio frequency power at a magnetic resonance frequency to the birdcage coil (144) via a plurality of M activation ports (158) selected out of the plurality of N activation ports (158). In an operational state of the birdcage coil (144) each radio frequency amplifier unit (142) is electrically connected and is arranged in close proximity to an activation port (158). Among the plurality of M radio frequency amplifier units (142), there is established a fixed relationship of adjustable phase angles (φ) of the magnetic resonance radio frequency power provided by the plurality of M radio frequency amplifier units (142); a method of generating and applying a radio frequency excitation field B for the purpose of magnetic resonance examination, using such magnetic resonance radio frequency transmission device (140); and a magnetic resonance imaging system (110) configured for acquiring magnetic resonance images of at least a portion of a subject of interest (120), comprising such magnetic resonance radio frequency transmission device (140).