MRI T1 Mapping Pulse Sequence Combining Inversion and Saturation
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Solution Overview
Problem
Current magnetic resonance imaging techniques for creating T1 maps either require long waiting periods due to reliance on inversion pulses or compromise on signal-to-noise ratio when using saturation pulses alone, leading to inefficient measurement times and reduced accuracy in determining T1 relaxation times.
Innovation Solution
A pulse sequence that combines inversion and saturation pulses, where the saturation pulses follow the inversion pulse to rapidly sample the relaxation curve, allowing for shorter measurement times and improved signal-to-noise ratio by coordinating the pulses to cover a broader range of T1 relaxation times without waiting for full relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only inversion pulses are used for preparation of longitudinal magnetization, then measurement accuracy is improved, but measurement time increases due to long waiting periods required for full relaxation
Solution Approach 1:
The patent combines inversion pulses and saturation pulses in a single exposure cycle. The inversion pulse is applied first to invert the longitudinal magnetization, followed by saturation pulses that rapidly dephase the magnetization. This merging of two preparation techniques allows the system to benefit from both the accuracy of inversion pulses and the time efficiency of saturation pulses, resolving the contradiction between measurement accuracy and measurement time.
Solution Approach 2:
The inversion pulse is applied in advance at the beginning of the exposure cycle, initiating the relaxation process early. Subsequent saturation pulses then sample the relaxation curve at multiple time points without requiring waiting for complete relaxation. This preliminary action of inverting the magnetization early allows for accelerated sampling and reduces the total measurement time while maintaining accuracy.
2Loss of time
If only saturation pulses are used for preparation of longitudinal magnetization, then measurement time is reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent merges inversion pulses and saturation pulses to combine their advantages. The inversion pulse provides strong initial magnetization inversion that improves signal strength and noise ratio, while the subsequent saturation pulses maintain short measurement time by rapidly sampling the relaxation curve. This combination resolves the contradiction between measurement time and signal-to-noise ratio.
Solution Approach 2:
The pulse sequence creates a composite preparation scheme that integrates two different pulse types (inversion and saturation) into a unified sequence. This composite approach leverages the complementary strengths of both pulse types: inversion pulses for signal strength and saturation pulses for time efficiency, thereby achieving both high signal-to-noise ratio and short measurement time.
3Productivity
If saturation pulses are applied before inversion pulses, then rapid sampling is achieved, but longitudinal magnetization history is not properly reset leading to measurement errors
Solution Approach 1:
The patent inverts the conventional order of operations by applying the inversion pulse first, then followed by saturation pulses. This reversal ensures that the longitudinal magnetization is properly inverted and reset before saturation occurs, eliminating measurement errors while maintaining rapid sampling efficiency. The inversion pulse establishes a clean starting point that the subsequent saturation pulses can then efficiently sample.
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 more accurate and efficient determination of T1 relaxation times by maximizing signal efficiency and reducing measurement time, while maintaining a high signal-to-noise ratio, allowing for precise T1 mapping.
Implementation Method 1
In magnetic resonance imaging, frequently T1 relaxation times are quantitatively determined and spatially resolved as a T1 map. The T1 relaxation time, also called spin-lattice relaxation time, is the time that the longitudinal magnetization of the nuclear spins requires in order to return to approximately 63% of its initial value after an excitation from the state of equilibrium.
Implementation Method 2
The T1 relaxation time, also called spin-lattice relaxation time, is the time that the longitudinal magnetization of the nuclear spins requires in order to return to approximately 63% of its initial value after an excitation from the state of equilibrium.
Data Source
AI summary
In a method and apparatus for magnetic resonance imaging, in order to create a T1 map, an pulse sequence is used that includes at least one exposure cycle, wherein the exposure cycle includes an inversion pulse, a saturation pulse quantity of one or more saturation pulses and a readout step quantity of one or more readout steps. Within the exposure cycle, at least one saturation pulse of the saturation pulse quantity follows the inversion pulse and at least one readout step of the readout step quantity follows the at least one saturation pulse.