TEM Resonator System with Intermediate RF Shield for MRI Homogeneity
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Solution Overview
Problem
The profile of RF field strength and homogeneity is adversely affected by the division of birdcage coils into separate parts, and there is a need for an RF resonator system that can maintain homogeneity while allowing supplementary elements like PET detectors to be positioned close by without compromising the RF field profile.
Innovation Solution
A system comprising multiple TEM cylindrical volume resonators arranged along a common longitudinal axis with intermediate RF shields to prevent electromagnetic energy from radiating outward, allowing a supplementary element to be placed between them, and providing electromagnetic decoupling to maintain field homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If birdcage coils are divided into separate parts to allow supplementary elements like PET detectors to be positioned close by, then adaptability and accessibility are improved, but RF field homogeneity deteriorates
Solution Approach 1:
The RF resonator system is divided into multiple independent TEM resonator units arranged along the longitudinal axis. Each unit can be independently controlled and positioned, allowing supplementary elements to be placed between units while maintaining overall system functionality and RF field homogeneity through coordinated operation of the segmented units.
Solution Approach 2:
Intermediate structures or coupling mechanisms are introduced between adjacent TEM resonator units to maintain electromagnetic coupling and field continuity. These intermediaries ensure that the division into separate parts does not compromise RF field homogeneity, as they mediate the electromagnetic interaction between segmented units.
2Manufacturing precision
If multiple TEM resonators are arranged along a common longitudinal axis to maintain field homogeneity, then RF field homogeneity is improved, but device complexity increases
Solution Approach 1:
Each TEM resonator unit is designed as a universal module that can serve multiple functions: generating RF fields, providing electromagnetic shielding, and acting as a structural support. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while maintaining RF field homogeneity across the extended longitudinal arrangement.
Solution Approach 2:
Adjacent TEM resonator units are electromagnetically coupled to function as an integrated system. By merging their electromagnetic fields through controlled coupling, the system achieves homogeneous RF field distribution across the entire longitudinal axis, effectively managing complexity through functional integration rather than physical consolidation.
3Object-affected harmful factors
If intermediate RF shields are added to prevent electromagnetic energy from radiating outward, then RF field containment is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
RF shielding structures are pre-integrated into the design of each TEM resonator unit and intermediate sections during manufacturing. This preliminary incorporation of shielding measures simplifies final assembly, as the shielding functionality is already built-in rather than requiring separate installation steps, thereby improving ease of manufacture while maintaining effective electromagnetic containment.
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 achieves a more homogeneous RF field profile and enables the placement of supplementary elements like PET detectors in close proximity without degrading the RF field homogeneity, supporting multi-element transmit/receive imaging with independent control of RF currents.
Implementation Method 1
TEM resonators which are electromagnetically decoupled from each other by means of intermediate RF shields
Implementation Method 2
transmitting an RF excitation pulse (Bi field) which is orthogonal to the Bo field, generated by means of an RF transmit antenna or coil
Implementation Method 3
electromagnetically decoupled from each other by means of intermediate RF shields arranged in the intermediate section
Implementation Method 4
The shapes and dimensions in cross sections of the first and of the second RF shield and their axial lengths are selected such that a homogeneous RF field distribution is obtained
Data Source
Figure 1
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AI summary
A TEM resonator system is disclosed comprising at least two TEM resonators (21,31; 22, 32), especially in the form of TEM volume coils, and especially for use in an MR imaging system or apparatus for transmitting RF excitation signals and/or for receiving MR signals into/from an examination object or a part thereof, respectively, wherein the TEM resonators are arranged and displaced along a common longitudinal axis and wherein an intermediate RF shield (4) is positioned in longitudinal direction between the two TEM resonators for at least substantially preventing electromagnetic radiation from emanating from between the first TEM resonator and the second TEM resonator into the surroundings. A PET detector and/or another supplementary element can be placed in the volume between the two TEM resonators.