Low-field Magnetic Resonance Fingerprinting Dictionary Optimization
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Solution Overview
Problem
Current magnetic resonance fingerprinting (MRF) methods are not optimized for low-field magnetic resonance systems, which have magnetic field strengths less than 1.5 tesla, leading to inefficiencies in determining parameter values due to the complexity of signal characteristics and long scanning times.
Innovation Solution
An MRF method adapted for low-field systems that reduces the size of the comparison signal characteristics dictionary by omitting or minimizing the dimensions of the constant magnetic field B0 and transmit field B1, using a balanced steady-state free precession (bSSFP) pulse sequence, and optimizing repetition times to avoid stopbands and artifacts, allowing for efficient determination of parameter values with high signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRF methods are used on low-field systems, then parameter determination can be performed, but computing effort and scanning time increase significantly
Solution Approach 1:
The patent changes the parameters of the comparison signal characteristics dictionary by omitting or minimizing dimensions related to constant magnetic field B0 and transmit field B1, which are less critical in low-field systems. This parameter reduction directly decreases computing effort while maintaining adequate measurement precision for low-field applications
Solution Approach 2:
The patent applies local quality optimization by tailoring the dictionary construction specifically for low-field conditions (B0 < 1.5 Tesla). Instead of using a universal high-field optimized dictionary, the solution creates a specialized dictionary that matches the local characteristics of low-field systems, improving efficiency without sacrificing accuracy
2Measurement precision
If conventional MRF methods are used on low-field systems, then parameter determination can be performed, but computing complexity increases
Solution Approach 1:
The patent reduces computing complexity by changing the dimensional parameters of the comparison signal characteristics dictionary. Specifically, it omits or minimizes the dimensions of constant magnetic field B0 and transmit field B1, which significantly reduces the dictionary size and associated computational burden while maintaining sufficient accuracy for low-field parameter determination
3Illumination intensity
If standard pulse sequences are used, then signal excitation can be achieved, but stopbands and banding artifacts occur due to off-resonance effects
Solution Approach 1:
The patent employs periodic action through carefully designed pulse sequences with specific repetition times (TR) that are optimized for low-field conditions. By setting TR such that the excitation frequency and its harmonics fall within passbands rather than stopbands, the method periodically excites spins in a manner that avoids off-resonance banding artifacts while maintaining strong signal intensity
Solution Approach 2:
The patent uses dynamic adjustment of pulse sequence parameters, particularly repetition time TR and flip angles, to adapt to the specific resonance conditions of low-field systems. This dynamic optimization ensures that excitation pulses consistently target on-resonance spins while avoiding the creation of stopbands that would generate banding artifacts
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 significantly reduces computing effort and scanning time while maintaining high-quality parameter determination, leveraging the homogeneity of low-field systems to achieve efficient and precise measurements of tissue-specific parameters.
Implementation Method 1
the examination object is positioned in a magnetic resonance device in a comparatively strong static, homogeneous constant magnetic field, also called a B0 field... such that the nuclear spins thereof are aligned along the constant magnetic field. Radio-frequency excitation pulses (RF pulses) are irradiated into the examination object to trigger nuclear spin resonances
Implementation Method 2
using a balanced steady-state free precession (bSSFP) pulse sequence
Data Source
AI summary
A magnetic resonance fingerprinting (MRF) method for determining parameter values in pixels of an examination object can use a magnetic resonance system with, for example, a constant magnetic field strength (e.g. of less than 1.5 tesla or a constant magnetic field strength of less than 0.5 tesla). The MRF method can be adapted for conditions that prevail with such low-field magnetic resonance systems, thus enabling the parameter values to be advantageously determined efficiently while simultaneously maintaining a high degree of quality.