Transient MRI Signal Analysis Using Damped Oscillator Model
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Solution Overview
Problem
Current Magnetic Resonance Imaging (MRI) techniques face inefficiencies due to the slow establishment of a steady-state magnetization, leading to image artifacts and prolonged scan times, particularly during the transient phase of Steady-State MRI sequences.
Innovation Solution
The method treats the spin system as a linear and dissipative system, optimizing MRI sequences by analyzing the evolution of immediate responses rather than waiting for system equilibration, using a mathematical description equivalent to a 3D damped harmonic oscillator to derive optimal probing parameters and separate time-scales for TR, T2, and T1, allowing for faster image acquisition and improved contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steady-state MRI sequences are used to achieve stable magnetization, then image quality is improved, but scan time is prolonged due to slow establishment of steady-state
Solution Approach 1:
The patent applies preliminary action by using a catalyzing sequence before the main imaging sequence to pre-establish the steady-state magnetization. This preliminary action prepares the spin system in advance, so that when the imaging sequence begins, the steady-state is already established, eliminating the need to wait during the imaging acquisition and thus reducing total scan time while maintaining image quality.
Solution Approach 2:
The patent implements continuity of useful action by designing the catalyzing sequence to continuously drive the magnetization toward steady-state using repeated RF pulses with specific flip angles and timing. This continuous action efficiently establishes the steady-state condition without interruption, maximizing the rate at which useful magnetization is built up before imaging begins.
2Reliability
If waiting for magnetization to reach steady-state is implemented, then image artifacts are reduced, but productivity is decreased
Solution Approach 1:
The patent resolves this contradiction by performing the steady-state establishment action in advance through a dedicated catalyzing sequence. This separates the steady-state preparation from the imaging acquisition, ensuring that by the time imaging begins, the magnetization is already in steady-state, thereby eliminating artifacts during imaging while minimizing the time penalty to only the catalyzing sequence duration.
3Productivity
If transient phase imaging is performed to reduce scan time, then productivity is improved, but image artifacts increase
Solution Approach 1:
The patent eliminates transient phase artifacts by implementing preliminary action - the catalyzing sequence prepares the magnetization in advance to reach steady-state before the imaging sequence starts. This ensures that all imaging acquisitions occur during the steady-state phase, completely avoiding the oscillatory transient behavior that causes artifacts, while the total time penalty is limited to the catalyzing sequence itself.
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 enables faster and more efficient MRI imaging by optimizing the sequence design, providing better separation of time-scales and allowing for the derivation of intrinsic parameters, resulting in improved image quality and reduced scan time.
Implementation Method 1
the spin system may exhibit an evolution of responses similar to a damped oscillator... T1 (intrinsic parameter of the spin system, typically on the scale of 600-1200 ms)
Implementation Method 2
T2 (intrinsic parameter of the spin system, typically on the scale of 50-100 ms)
Implementation Method 3
the immediate response of the system (state of magnetization in the whole object) may in principle contain sufficient information to characterize the system
Data Source
AI summary
A method for magnetic resonance imaging (MRI) comprises applying a consecutive series of MRI sequences to a target volume (V) according to experimental settings (TR, α, β). A discrete sequence of transient response signals (Sn, Sn+1, Sn+2) is measured and fitted to a fit function (F) that is continuously dependent on a sequence number (n) of the respective MRI sequence (Pn) and corresponding response signal (Sn). A shape of the fit function is determined according to an analytically modelled evolution by the experimental parameters (TR, α, β) as well as variable intrinsic parameters (r, λ3, φ, δ) to be fitted. For example, the model is based on an equivalent harmonic oscillator. The intrinsic parameters of the fit function can be related to the intrinsic properties (PD, T1, T2) of the spin systems and used for imaging the target volume (V). Various optimizations of contrast can be achieved by tuning the experimental settings according to the model.