Switchable RF Shield for MRI Coil Decoupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems face challenges with coupling between antenna elements, leading to radiative losses and reduced sensitivity, especially in high-field applications, which affects image quality and patient safety due to unwanted radiation exposure.
Innovation Solution
A switchable radio-frequency (RF) shield is employed to decouple transmit/receive coil elements by switching between blocking and transparent states using PIN-diodes, reducing coupling and enhancing sensitivity during receive phases while minimizing radiation during transmit phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multichannel receive array is employed for improved signal reception, then signal reception sensitivity is improved, but coupling between antenna elements occurs leading to radiative losses
Solution Approach 1:
A radio frequency shield is introduced as an intermediary element positioned between adjacent antenna elements. The shield comprises multiple conductive elements connected by RF switches that can be configured in different states. During transmit mode, the shields are connected to block RF energy and prevent coupling between elements. During receive mode, the shields are disconnected to allow RF energy passage while maintaining decoupling through the shield structure itself, thereby reducing radiative losses while preserving signal reception sensitivity.
2Loss of energy
If the RF shield is in blocking state to prevent radiation losses, then radiative losses are reduced, but receive sensitivity deteriorates
Solution Approach 1:
The RF shield system employs dynamic switching capability through RF switches (such as PIN diodes) that can change the electrical connection state of conductive elements based on operational mode. During transmit mode, switches connect conductive elements to form a continuous shield that blocks RF energy and prevents radiative losses. During receive mode, switches disconnect conductive elements to create gaps that allow RF energy passage while the shield structure maintains decoupling between antenna elements, thus preserving receive sensitivity.
3Productivity
If coil elements are used for parallel transmission to improve productivity, then imaging speed is improved, but coupling between coil elements increases causing safety issues
Solution Approach 1:
The RF shield acts as an intermediary barrier between adjacent coil elements used for parallel transmission. The shield's conductive elements, when connected during transmit mode, block RF energy from leaking between elements, preventing unwanted radiation exposure to patients outside the field of view. This allows multiple coil elements to operate simultaneously for accelerated imaging while maintaining safety through the shielding effect.
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 effectively reduces coupling between coil elements, improves receive sensitivity, and confines electromagnetic radiation within the Field of View (FOV), leading to better image quality and reduced Specific Absorption Rate (SAR) performance, especially in high-field applications.
Implementation Method 1
a radio-frequency shield switchable between a blocking state and a transparent state... During the transmit phase the RF-screen is switched to a conventional, RF-blocking mode, thus preventing the coil element from radiating a significant amount of its driving RF power
Implementation Method 2
The conductive elements and the at least one radio-frequency switch form the radio-frequency shield... the switches connect the pieces of the RF-screen such that an RF-blocking behavior is achieved
Implementation Method 3
During the receive phase, suitable switches (e.g. PIN-diodes) open the RF-screen improving the receive sensitivity of each element
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention provides for a magnetic resonance imaging system (300, 400) for acquiring magnetic resonance data (342). The magnetic resonance imaging system comprises a coil assembly (319) configured for radiating and/or receiving radio frequency energy from an imaging zone. The coil assembly has a first surface (315) configured for being directed towards the imaging zone and comprises at least one coil element (317). The coil assembly further comprises a radio frequency shield (319) switchable between an RF blocking state (804) and an RF transparent state (802). The at least one coil element is between the first surface and the radio frequency shield. The switchable radio frequency shield comprises at least two conductive elements (322). The radio frequency shield comprises at least one radio frequency switch (324) configured for electrically connecting the at least two conductive elements in the blocking state and disconnecting the at least two conductive elements in the transparent state.