T1 Mapping for Short-T2 Tissues in MRI
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRI techniques struggle to accurately and efficiently map T1 relaxation times in biological tissues with short-T2 relaxation times, particularly in clinically practical scan times, due to rapid signal decay and sensitivity to B1-inhomogeneity.
Innovation Solution
The method involves performing magnetization preparation radio frequency pulse sequences with repetition time intervals, acquiring MRI signals using 3D readout blocks sensitive to short-T2 signals at different recovery times, and reconstructing images to map T1 values from multiple reconstructed images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI techniques are used for T1 mapping in short-T2 tissues, then T1 relaxation times can be measured, but the rapid signal decay causes loss of information and inaccurate measurements
Solution Approach 1:
The patent applies preliminary action by performing magnetization preparation (inversion or saturation) before the readout sequence. This prepares the magnetization state in advance so that the signal evolution during the ultra-short echo time readout contains the necessary T1 information, allowing accurate T1 mapping despite the rapid signal decay of short-T2 tissues
Solution Approach 2:
The patent implements skipping by using an ultra-short echo time (UTE) readout sequence that rapidly acquires the signal before it decays. The echo time is minimized to capture the signal from short-T2 tissues before the rapid decay causes information loss, effectively rushing through the acquisition window to preserve signal integrity
2Measurement precision
If repeated inversion-recovery experiments with spin-echo sequence are performed for accurate T1 mapping, then measurement precision improves, but acquisition time increases to clinically impractical levels
Solution Approach 1:
The patent merges the T1 preparation (inversion-recovery) with the T2*-sensitive ultra-short echo time readout into a single integrated sequence. This combination allows T1 mapping to be performed in 3D with significantly reduced acquisition time compared to conventional repeated spin-echo experiments, making it clinically practical while maintaining accuracy
Solution Approach 2:
The patent changes the echo time parameter to ultra-short values in the readout sequence. This parameter change enables the capture of signal from short-T2 tissues that would otherwise decay before conventional readout can acquire it, allowing accurate T1 mapping in reduced time
3Reliability
If standard MRI sequences are used for imaging, then general imaging can be performed, but B1-inhomogeneity causes signal intensity variations and reduces measurement reliability
Solution Approach 1:
The patent uses feedback by acquiring signals at multiple inversion times and using this information to calculate T1 maps that are inherently corrected for B1-inhomogeneity. The multi-time-point acquisition provides feedback data that allows separation of T1 effects from B1 scaling effects, improving measurement reliability
Solution Approach 2:
The patent changes the timing parameters (inversion times) in the sequence to multiple values. This parameter variation allows the system to capture signal evolution that is sensitive to T1 but can be differentiated from B1-inhomogeneity effects, thereby correcting for this harmful factor
4Measurement precision
If multiple readout blocks at different recovery times are implemented for T1 mapping, then T1 mapping accuracy for short-T2 tissues improves, but sequence complexity increases
Solution Approach 1:
The patent segments the readout into multiple blocks, each acquired at a different recovery time after magnetization preparation. This segmentation allows T1 information to be captured at multiple time points without requiring a completely complex new sequence, as each block can use the same basic ultra-short echo time readout structure
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 accurate T1 mapping in tissues with short-T2 relaxation times, reducing scan times and minimizing the impact of B1-inhomogeneity, making it suitable for clinical applications.
Implementation Method 1
performing magnetization preparation radio frequency pulse sequences with two successive magnetization preparation radio frequency pulse sequences being separated by a repetition time interval TR
Implementation Method 2
The signal detected in medical MRI is proportional to the transversal 1H nuclear spin magnetization. Once generated, it decays approximately exponentially with time constants T2*
Implementation Method 3
acquiring an MRI signal generated by the part of the biological object in response to a number N of 3D readout blocks sensitive to short-T2 signal
Implementation Method 4
mapping T1 values for the part from two or more of the reconstructed images... The most basic and probably most accurate approach for quantitative T1 mapping are repeated inversion-recovery (IR) experiments... After an (adiabatic) inversion pulse, the longitudinal magnetization exponentially approaches the equilibrium magnetization with the time constant T1
Data Source
AI summary
An MRI method and system for mapping T1 relaxation times of a biological object with a part having a short-T2 relaxation time. The MRI system first performs one or several magnetization preparation radio frequency pulse sequences, with successive RF pulse sequences being separated by a repetition time interval TR. The MRI system acquires an MRI signal generated by the part of said biological object during each repetition time interval TR in response to a plurality of 3D readout blocks generated by the MRI system and applied to the part of the biological object. For each readout block, an MRI signal is acquired by the MRI system at a different recovery time. Each readout block is sensitive to short-T2 signal. An image of the part is reconstructed from each MRI signal and T1 values are mapped for the part from at least two of said reconstructed images.