RF Receive Coil Array for Parallel Transmission in MRI
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Solution Overview
Problem
Existing MRI systems face challenges in generating a uniform B1 field, particularly at higher magnetic field strengths, due to the limitations of traditional quadrature-driven volume coils, which require costly multi-element transmit array coils and associated components for parallel transmission.
Innovation Solution
The system dynamically operates an array of RF receive coils in a transmit mode by using a detuning circuit to control their resonance and impedance, allowing them to generate a local RF field that adds to the whole-body transmit coil's field, thereby achieving the desired amplitude and phase of transverse MR magnetization without the need for a multi-element transmit array coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a multi-element transmit array coil is used for parallel transmission to homogenize the B1 field, then the uniformity of the B1 field is improved, but the hardware cost and device complexity significantly increase
Solution Approach 1:
Instead of using transmit coils to create a uniform B1 field, the invention uses receive coils operated in transmit mode. The receive coils are normally used for signal reception but are inverted to perform transmission functions, eliminating the need for a separate multi-element transmit array coil and its associated expensive hardware
Solution Approach 2:
The receive coils are designed to perform dual functions: signal reception during the receive phase and B1 field generation during the transmit phase. This multi-functionality eliminates the need for dedicated transmit array coils, reducing hardware costs while maintaining B1 field uniformity through parallel transmission
2Adaptability or versatility
If a multi-element transmit array coil with individual exciter boxes and RF amplifiers is implemented, then the ability to control amplitude and phase of individual transmit elements is improved, but the device complexity and hardware cost increase
Solution Approach 1:
The receive coil array performs both reception and transmission functions. During transmission, the same coil array that receives signals is used to generate the B1 field, eliminating the need for separate transmit array coils with their associated exciter boxes and RF amplifiers, thereby reducing hardware complexity while maintaining control capabilities
Solution Approach 2:
The invention merges the transmit and receive coil functions into a single coil array. By combining these functions, the system eliminates redundant hardware components such as individual exciter boxes and RF amplifiers for each transmit element, reducing overall device complexity while preserving the ability to control amplitude and phase
3Device complexity
If traditional quadrature-driven volume coils are used for B1 field excitation, then the system simplicity is maintained, but the uniformity of the B1 field deteriorates, especially at higher field strengths
Solution Approach 1:
Instead of using a single volume coil for B1 field excitation, the invention segments the field generation into multiple receive coil elements that can be independently controlled. Each coil element contributes to the overall B1 field, allowing for spatially tailored RF pulses and gradient combinations that homogenize the field, particularly at higher field strengths like 3T and 7T
Solution Approach 2:
The invention changes the operational parameters of the coil array by switching receive coils into transmit mode using detuning circuits. This parameter change allows the system to achieve B1 field homogenization through parallel transmission while maintaining relative system simplicity, overcoming the limitations of traditional quadrature-driven volume coils
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 provides a cost-effective method to achieve a uniform B1 field, reducing hardware costs by eliminating the need for individual exciter boxes and independent RF amplifiers, while maintaining high fidelity in magnetization tipping and image quality.
Implementation Method 1
a detuning circuit coupled to each RF receive coil in the array of RF receive coils that is selectively switched between a disabled and an enabled state to control a resonance and impedance of the RF receive coil
Implementation Method 2
an RF transmit coil disposed within the bore of the main magnet and configured to generate an RF field, with the RF field exciting nuclei of a subject positioned within the bore to generate RF resonance signals
Data Source
AI summary
A system and method for selectively operating an array of RF receive coils in a transmit mode is disclosed. The system includes an RF transmit coil configured to generate an RF field that excites nuclei of a subject to generate RF resonance signals, an array of RF receive coils to receive the RF resonance signals, and a detuning circuit coupled to each RF receive coil in the array of RF receive coils that is selectively switched between a disabled and an enabled state to control a resonance and impedance of the RF receive coil. Each RF receive coil is caused to receive RF resonance signals when its respective detuning circuit is in the disabled state and is caused to modify an amplitude and phase of the RF field generated by the RF transmit coil when its respective detuning circuit is in the enabled state.