MRI Multi-Parameter Mapping Using Material-Specific RF Pulse Sequences
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Solution Overview
Problem
Current MRI technologies face challenges in reducing scan time and accurately distinguishing and quantifying signals from different materials, particularly fat and those with large off-resonance, leading to signal-to-noise ratio loss and reduced reliability in parameter quantification.
Innovation Solution
The method involves applying RF pulses with specific repetition times determined based on the materials to increase orthogonality between signals, allowing for undersampling and effective matching with a signal model for multi-parameter mapping, thereby enhancing the separation and quantification of MR signals from different materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If pseudorandomized flip angle and repetition time are used to enable multi-parameter mapping, then scan time is reduced and parameter quantification is enabled, but signal-to-noise ratio is lost and parameter quantification reliability is reduced
Solution Approach 1:
The patent applies parameter changes by systematically varying flip angles and repetition times in a controlled manner to generate unique signal evolutions for different materials. This allows multi-parameter mapping to be performed while maintaining signal quality and quantification reliability, resolving the contradiction between scan time reduction and reliability maintenance.
Solution Approach 2:
The patent uses periodic RF pulse sequences with specific repetition times to generate characteristic signal evolutions. By employing periodic actions with optimized parameters, the method achieves both rapid data acquisition and reliable parameter quantification through pattern recognition and matching.
2Loss of time
If pseudorandomized acquisition technique is used for multi-parameter mapping, then scan time is shortened, but MR signals from different materials cannot be clearly distinguished
Solution Approach 1:
The patent applies local quality by tailoring the RF pulse sequence parameters (flip angles, repetition times) to the specific magnetic properties of different materials being imaged. This material-specific optimization enables clear distinction of signals from different materials while maintaining rapid acquisition through efficient sampling strategies.
Solution Approach 2:
The patent employs feedback mechanisms where the acquired MR signals are compared against a library of simulated signal evolutions. This pattern matching process provides feedback that enables accurate material identification and parameter quantification even with accelerated acquisition, resolving the contradiction between speed and precision.
3Measurement precision
If fat signal or signal with large off-resonance is quantified using traditional techniques, then parameter quantification is attempted, but signal-to-noise ratio loss occurs and quantification accuracy is reduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing a comprehensive library of simulated signal evolutions for various materials with different magnetic properties including fat and off-resonance signals. This pre-prepared reference library enables accurate matching and quantification of challenging signals without requiring repeated measurements, thus maintaining both accuracy and signal-to-noise ratio.
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 effectively suppresses signal-to-noise ratio loss, improves the separation of MR signals from different materials, and reduces the probability of errors in parameter quantification, enabling more reliable and efficient MRI scans.
Implementation Method 1
An MRI apparatus uses a magnetic field to capture an image of a subject
Implementation Method 2
by using a pulse sequence for generating RF signals, RF signals may be applied to an object via the RF multi-coil
Data Source
AI summary
Provided are a method and apparatus for processing a magnetic resonance (MR) image of an object including first and second materials on a magnetic resonance imaging (MRI) apparatus by using multi-parameter mapping including applying to the object a plurality of radio frequency (RF) pulses separated by a first repetition time and a second repetition time, the first repetition time and the second repetition time being determined based on the first material and the second material; undersampling first MR signals corresponding to the first material and second MR signals corresponding to the second material in a K-space; and performing matching between the undersampled first and the undersampled second MR signals and a signal model for the multi-parameter mapping to determine attribute values corresponding to the first and the second materials at at least one point in an MR image of the object.