Segmented MR Body Coil for Homogeneous RF Field Generation
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Solution Overview
Problem
Magnetic resonance apparatuses face challenges with timing inefficiencies and increased specific absorption rate (SAR) due to the need for additional saturation pulses, which also lead to image artifacts from rephased magnetization.
Innovation Solution
The apparatus generates a homogeneous radio-frequency magnetic field only in specific sub-volumes of the examination area, eliminating the need for saturation pulses by activating resonator segments to create a tailored excitation field that avoids unnecessary RF exposure, thereby reducing SAR and preventing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If saturation pulses are used to suppress specific body regions, then motion artifacts are reduced, but the imaging time is doubled and SAR increases
Solution Approach 1:
The body coil is divided into multiple resonator segments that can be independently controlled and activated. This segmentation allows the RF field to be applied only to specific regions of interest, eliminating the need for separate saturation pulses and reducing total imaging time while maintaining image quality.
Solution Approach 2:
Different regions of the examination volume are treated differently by activating only the resonator segments corresponding to the region of interest. This local control enables selective excitation without requiring global saturation pulses, thereby reducing imaging time and SAR while preserving diagnostic image quality in the target region.
2Reliability
If saturation pulses are applied to dephase magnetization in specific regions, then artifacts from those regions are suppressed, but additional energy is radiated increasing SAR
Solution Approach 1:
The harmful effect of unnecessary RF exposure is eliminated by extracting or removing the saturation pulse step from the imaging sequence. Instead of applying RF energy to suppress artifacts, the system simply does not activate resonator segments in regions that would cause artifacts, thereby reducing SAR while maintaining image quality.
Solution Approach 2:
RF energy is applied locally only to regions requiring imaging, with resonator segments selectively activated based on the examination protocol. This localized energy application eliminates the need for additional saturation pulses, reducing overall SAR while preserving diagnostic image quality in the target region.
3Area of stationary object
If the entire examination volume is excited by RF field, then complete coverage is achieved, but time is lost due to sequential saturation and excitation sequences
Solution Approach 1:
The body coil is segmented into multiple independently controllable resonator segments, allowing simultaneous or selective excitation of different regions. This enables complete examination volume coverage to be achieved through parallel or optimized sequential activation of segments, eliminating the time penalty of separate saturation and excitation sequences.
Solution Approach 2:
The system pre-selects which resonator segments to activate based on the desired examination region and protocol. By determining the optimal segment activation pattern in advance, the system eliminates the need for time-consuming saturation pulses and achieves both complete coverage and high imaging speed.
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 accelerates the imaging sequence, reduces SAR exposure, and enhances image quality by ensuring that the RF field is only generated where needed, minimizing artifacts and optimizing field homogeneity for improved diagnostic information.
Implementation Method 1
a control device for separate activation of the individual resonator segments (the resonator segments being electromagnetically decoupled from one another) so as to generate a radio-frequency field inside the coil for magnetic resonance (MR) spin excitation
Implementation Method 2
the resonator segments being electromagnetically decoupled from one another such that each resonator segment can be separately activated by a control device
Data Source
AI summary
A magnetic resonance apparatus has a cylindrical body coil composed of a number of resonator segments distributed around the circumference and a control device for separate activation of the individual resonator segments. The resonator segments are electromagnetically decoupled from one another. The activation generates a radio-frequency magnetic field inside the coil for spin excitation in an examination volume. The resonator segments are activated such that the excitation field is generated only in at least one first sub-volume forming the examination volume, and at least one second sub-volume, that is not to be excited, is essentially free of the excitation field.