Multi-Nuclei RF Antenna Arrangement for Parallel MRI
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Solution Overview
Problem
Simultaneous magnetic resonance imaging of nuclei with different gyromagnetic ratios introduces severe back-folding artifacts due to differing fields of view, especially when using the same gradient magnet fields for all nuclei.
Innovation Solution
A multi-nuclei RF antenna arrangement with separate antennas for each species of nuclei, each with a distinct number of antenna elements resonant to their respective Larmor frequencies, and using Parallel Imaging techniques to extend the field of view and prevent back-folding artifacts, allowing for simultaneous imaging without disturbing the common MR image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same gradient magnet fields are used for all nuclei species, then imaging efficiency is improved, but back-folding artifacts occur due to differing fields of view
Solution Approach 1:
The patent divides the imaging system into separate antennas for different nuclei species (e.g., 31P antenna and 1H antenna), each with its own signal processing chain. This segmentation allows independent field of view adjustment for each nucleus type while maintaining efficient simultaneous imaging, resolving the contradiction between imaging efficiency and artifact prevention.
2Object-affected harmful factors
If separate antennas are used for different nuclei species, then back-folding artifacts are prevented, but device complexity increases
Solution Approach 1:
The patent employs a universal imaging framework where multiple antennas (31P, 1H, etc.) share common gradient magnet fields and imaging protocols. This multi-functionality approach allows the system to handle different nuclei species with a unified architecture, reducing complexity compared to completely separate imaging systems while still preventing back-folding artifacts through species-specific field of view management.
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
Enables simultaneous MR imaging of nuclei with different gyromagnetic ratios using the same gradient magnet fields, preventing back-folding artifacts and enhancing spatial sensitivity, thereby generating accurate and undisturbed MR images for all species.
Implementation Method 1
the magnetic moments of the nuclei within the examination object tend to rotate around the axis of the applied B0 field (Larmor precession) with a certain net magnetization of all nuclei parallel to the B0 field. The rate of precession is called Larmor frequency which is dependent on the specific physical characteristics of the involved nuclei, namely their gyromagnetic ratio
Implementation Method 2
By transmitting an RF excitation pulse (B1 field) which is orthogonal to the B0 field, generated by means of an RF transmit antenna, and matching the Larmor frequency of the nuclei of interest, the spins of the nuclei are excited and brought into phase
Implementation Method 3
After termination of the RF excitation pulse, the relaxation processes of the longitudinal and transversal components of the net magnetization begin, until the net magnetization has returned to its equilibrium state. MR relaxation signals which are emitted by the transversal relaxation process, are detected by means of an MR/RF receive antenna
Data Source
Figure 1~2
AI summary
A multi nuclei RF antenna arrangement for use in a multi nuclei MRI system or an MR scanner, for transmitting RF excitation signals (B1 field) for exciting nuclear magnetic resonances (NMR), and/or for receiving NMR relaxation signals for multi nuclei MR (magnetic resonance) image reconstruction is disclosed, wherein the RF antenna arrangement is tuned to the Larmor frequencies of at least two different species of nuclei having at least two different gyromagnetic rations like 1H, 14N, 31P, 13C, 23Na, 39K, 17O and hyperpolarized gases like 129Xe or other isotopes having a nuclear spin. Further, a method for reconstructing a multi nuclei MR image especially by means of the above RF antenna arrangement is disclosed. The method involves reducing back-folding artifacts of the species having the higher gyromagnetic ration by parallel MRI reconstruction.