Magnetic Resonance Imaging Magnetization Reset Sequence
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Solution Overview
Problem
Magnetic Resonance Fingerprinting (MRF) techniques face challenges in accurately estimating MR parameters like T1 and T2 due to difficulties in reproducing initial magnetization conditions, leading to increased imaging time and reduced throughput, as existing methods require long waiting times or incomplete magnetization reset.
Innovation Solution
The implementation of a zero-magnetization sequence that applies RF magnetic field pulses and spoiler gradient field pulses to reset longitudinal and transverse magnetization to zero, allowing for efficient initialization of magnetization without long waiting times, thereby enabling accurate MRF sequence execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long waiting times are used to reset magnetization, then magnetization initialization accuracy is improved, but imaging time increases
Solution Approach 1:
The patent applies preliminary action by implementing a magnetization reset sequence before the main MRF acquisition. This sequence uses RF pulses and gradient pulses to proactively reset longitudinal and transverse magnetization to known initial states, eliminating the need for long waiting periods and ensuring accurate initialization conditions for quantitative parameter estimation.
Solution Approach 2:
The patent utilizes parameter changes by varying RF pulse flip angles and gradient pulse parameters during the reset sequence. By dynamically adjusting these parameters, the system efficiently drives magnetization to the desired initial state (Mz=0, Mxy=0) much faster than natural relaxation, thereby reducing imaging time while maintaining initialization accuracy.
2Productivity
If magnetization is not fully reset, then imaging time is reduced, but estimation accuracy of MR parameters deteriorates
Solution Approach 1:
The patent implements feedback by using spoiler gradient pulses that actively dephase any remaining transverse magnetization. This feedback mechanism ensures that even if magnetization is not completely reset by the primary RF pulses, the gradient-induced dephasing provides an additional layer of assurance that initial conditions are properly established, maintaining estimation accuracy without sacrificing throughput.
3Measurement precision
If complex magnetization reset sequences are used, then initialization accuracy is improved, but sequence complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the magnetization reset process into distinct functional segments: (1) RF pulse segments that flip magnetization, (2) gradient pulse segments that dephase transverse components, and (3) combination segments that achieve complete reset. This modular segmentation makes the complex reset process more manageable and easier to implement while maintaining high initialization accuracy.
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 reduces imaging time, improves estimation accuracy of MR parameters, and enhances the efficiency of MRF by allowing for precise initialization of magnetization conditions, thus improving the overall throughput of MR imaging processes.
Implementation Method 1
a zero-magnetization sequence in which macroscopic longitudinal magnetization and transverse magnetization are reduced by applying a plurality of RF magnetic field pulses
Implementation Method 2
a plurality of spoiler gradient field pulses
Data Source
AI summary
A magnetic resonance imaging apparatus according to the present embodiment includes sequence control circuitry and processing circuitry. The sequence control circuitry controls execution of a pulse sequence which includes a first segment and a second segment being provided prior to the first segment. The first segment is where signal acquisition is performed. The second segment is where longitudinal magnetization and transverse magnetization are reduced by applying a plurality of RF magnetic field pulses while changing a magnitude and/or a phase thereof and a plurality of spoiler gradient field pulses.