MRI T1 Mapping Using Multiple Flip Angles
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Solution Overview
Problem
Existing MRI systems face challenges in generating a single T1 mapping that incorporates data from both inversion recovery (IR) and saturation recovery (SR) techniques, as they typically use limited flip angles such as 180° and 90°, making it difficult to combine data effectively.
Innovation Solution
The method involves transmitting preparation pulses with multiple flip angles into an object, receiving corresponding MR signals, and generating a T1 mapping using a combination of these signals, allowing for the integration of data from both IR and SR techniques by using different flip angles, such as 180° and 90°, to create a more comprehensive mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If only inversion recovery (IR) or saturation recovery (SR) is used with fixed flip angles of 180° or 90°, then the preparation pulse sequence is simple, but it is difficult to generate a single T1 mapping that incorporates data from both IR and SR techniques
Solution Approach 1:
The patent implements a universal T1 mapping method that can handle multiple recovery techniques (both IR and SR) within a single framework. The system uses a lookup table that stores pre-calculated signal intensity values for various flip angles and delay times, allowing the same T1 mapping algorithm to process data from different preparation pulse sequences. This multi-functional approach enables the system to incorporate data from both IR (180° flip angle) and SR (90° flip angle) techniques into a unified T1 mapping, resolving the contradiction between versatility and complexity.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing signal intensity values in a lookup table before actual T1 mapping is performed. The lookup table contains pre-computed values for various flip angles and delay time combinations, which are generated using the T1 mapping model equation. During actual operation, the system simply queries this pre-prepared table rather than performing complex real-time calculations, thereby reducing the computational complexity while maintaining the ability to handle multiple flip angles and recovery techniques.
2Measurement precision
If multiple flip angles are used to generate comprehensive T1 mapping, then the dynamic range and accuracy are improved, but the data processing complexity increases
Solution Approach 1:
The patent pre-calculates signal intensity values for multiple flip angles and delay times and stores them in a lookup table before actual T1 mapping is performed. This preliminary computation phase separates the complex mathematical operations from the real-time measurement process. During actual T1 mapping, the system only needs to query the pre-computed table and compare measured signals with stored values, dramatically reducing processing complexity while maintaining high measurement precision through the use of multiple flip angles.
Solution Approach 2:
The patent creates a virtual model of the MR signal behavior through the lookup table, which contains copied and stored signal intensity values for various flip angles and delay times. Instead of performing complex forward calculations during T1 mapping, the system copies relevant pre-computed values from the lookup table that match the actual measurement conditions. This copying approach simplifies the measurement process while preserving the accuracy benefits of using multiple flip angles.
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 the generation of T1 mappings that leverage the strengths of both IR and SR techniques, providing a greater dynamic range and improved accuracy by utilizing a plurality of flip angles, thereby overcoming the limitations of traditional methods.
Implementation Method 1
MRI is a widely accepted and commercially available technique for obtaining digitized visual images representing the internal structure of objects having substantial populations of atomic nuclei that are susceptible to nuclear magnetic resonance ('NMR')
Implementation Method 2
The nuclei are excited by a radio frequency ('RF') signal/pulse transmitted by a RF coil at characteristics NMR (Larmor) frequencies
Data Source
AI summary
A method of magnetic resonance imaging an object utilizing a plurality of flip angles is provided. The method includes transmitting a first preparation pulse corresponding to a first flip angle of the plurality into the object, and receiving a first MR signal from the object based at least in part on the first preparation pulse. The method further includes transmitting a second preparation pulse corresponding to a second flip angle of the plurality into the object, receiving a second MR signal from the object based at least in part on the second preparation pulse, and generating a T1 mapping of the object based at least in part on the first MR signal and the second MR signal. The second flip angle is different than the first flip angle.