U-Shaped TEM RF Coil for MRI Noise Reduction
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Solution Overview
Problem
Conventional quadrature birdcage coils in MR systems face issues with RF power supply due to hot connections, unreliable EM simulation, and challenging SAR management, particularly with degenerate coils, leading to noise pickup and increased RF power requirements.
Innovation Solution
A transverse-electromagnetic (TEM) RF coil with elongate strip sections arranged in a U-shaped configuration, featuring lateral extensions that reduce sensitivity along the z-axis, providing a defined RF ground and simplified decoupling, which reduces noise pickup, SAR, and RF power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrature birdcage coils are used, then signal-to-noise ratio is improved and field of view in z-direction is reduced, but RF power supply becomes problematic due to hot connections and SAR management becomes difficult
Solution Approach 1:
The coil is divided into multiple independent TEM resonator elements arranged in an array, each element being independently fed through coaxial cables. This segmentation eliminates the hot connection problem by providing separate, well-defined RF feed points for each element, while maintaining the high SNR through coherent signal combination.
Solution Approach 2:
Coaxial cables are introduced as intermediary components to feed RF power to each TEM resonator element. These cables provide well-defined RF connections with controlled impedance, acting as intermediaries between the RF source and the coil elements, thereby eliminating hot connection issues while maintaining reliable power supply.
2Use of energy by moving object
If conventional TEM coils are used, then RF power requirements are reduced, but noise pickup from regions outside imaging field of view increases
Solution Approach 1:
Each TEM resonator element is designed with specific geometric characteristics (parallel strip sections with lateral extensions forming U-shapes) that create localized electromagnetic field confinement. This local quality optimization ensures that each element contributes to the desired imaging region while minimizing sensitivity to regions outside the field of view, thereby reducing noise pickup.
3Length of stationary object
If degenerate birdcage coils are used, then field of view in z-direction is reduced, but SAR management becomes problematic and RF cable connections are difficult to define for simulation
Solution Approach 1:
The complex RF cable connection definition problem is replaced by using standardized coaxial cable feeds with well-defined impedance characteristics. Each TEM resonator element has clearly defined RF input terminals that accept standard coaxial connectors, making the system straightforward to model in electromagnetic simulations and eliminating the complexity of defining degenerate birdcage coil cable connections.
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 TEM coil design reduces noise reception and SAR, lowers RF power requirements, and simplifies decoupling, offering a safer and more efficient MR system with improved signal transmission and reception characteristics.
Implementation Method 1
both of the opposite end regions of the strip section of each TEM coil element have a lateral extension transverse to the longitudinal extent of the strip section, thereby providing each TEM coil element with a generally U-shaped configuration... the elements of a conventional or classical TEM coil are modified in such a way, that the strip section of each TEM coil element is extended laterally (e.g. azimuthally or circumferentially) at both of its opposite ends before connection to an RF shield or screen. Each of these extensions or additional parts of the coil elements has been found to produce field contributions that lead to reduced sensitivity along the z-axis during signal transmission and therefore to less noise pickup from regions outside the imaging field of view during signal reception
Implementation Method 2
both of the opposite end regions of the strip section of each TEM coil element have a lateral extension transverse to the longitudinal extent of the strip section, thereby providing each TEM coil element with a generally U-shaped configuration... arranged within and encompassed by an RF shield or screen, which functions as an RF ground for the coil
Data Source
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AI summary
The present invention provides a transverse-electromagnetic (TEM) radio-frequency coil (1) for a magnetic resonance system, especially for a magnetic resonance imaging system.In particular, the inventive concept provides a coil (1) in which at least one of the opposite end regions of the elongate strip section (4) of each TEM coil element (2) has a lateral extension (6) transverse to a longitudinal extent of the strip section (4). These lateral extensions (6) combine with strip sections (4) to form L-or U-shaped TEM coil elements (2) and provide 'ring-like' current contributions resulting in a reduction of the z-sensitivity compared with a conventional TEM coil. The result is a coil array having TEM coil elements (2) that provide smaller sensitivity profiles in the z-direction, yet preserve the characteristics of a well-defined RF ground, e.g. via an RF shield or screen (3).The reduced field of view in z-direction not only reduces noise reception but also reduces the SAR generated in those regions during transmission.