Magnetic Resonance Gradient Modulation for Ultra-Short Echo Times
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Solution Overview
Problem
Existing magnetic resonance (MR) methods, such as zTE and PETRA, are unable to record measurement data with different echo times of less than 500 μs in a short time, which limits the determination of decay constants shorter than 500 μs.
Innovation Solution
A method that involves increasing a gradient to a first strength, irradiating an RF excitation pulse, reducing the gradient strength, and then increasing it again to a desired strength for recording MR signals, allowing for adjustable echo times, including those less than 500 μs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sequences (SE or GRE) are used, then standard imaging is achieved, but substances with T2* time significantly shorter than echo times cannot be represented as signal decayed before recording
Solution Approach 1:
The gradient is increased to a first strength before the RF excitation pulse is irradiated, so that the encoding field is already prepared and optimized for ultra-short echo time measurement. This preliminary gradient preparation allows the measurement to start immediately after excitation without waiting for gradient ramp-up, enabling capture of signals from substances with T2* times shorter than conventional echo times.
2Loss of time
If zTE or PETRA sequences with radial spokes are used, then very short echo times are achieved, but an area in the center of k-space cannot be scanned by radial spokes
Solution Approach 1:
The gradient strength is dynamically adjusted during the measurement sequence. The gradient is increased to a first strength before excitation, then reduced after excitation, and finally increased to a second strength for data recording. This dynamic gradient modulation enables flexible control of the k-space trajectory, allowing both ultra-short echo time measurement and complete coverage of the central k-space area.
3Adaptability or versatility
If gradient strength is reduced after RF excitation pulse, then adjustable echo times including less than 500 μs are achieved, but additional gradient switching is required
Solution Approach 1:
The gradient strength parameter is changed at different stages of the measurement sequence. By increasing the gradient to a first strength before excitation, reducing it after excitation, and then increasing it to a second strength for recording, the echo time can be precisely controlled. This parameter modulation enables adjustable echo times including ultra-short times less than 500 μs while maintaining systematic control over the measurement process.
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 method enables the recording of measurement data with different but very short echo times, making the data comparable and allowing for the determination of decay constants shorter than 500 μs.
Implementation Method 1
For the local encoding of the measurement data, fast-acting magnetic gradient fields, referred to as gradients for short, are usually superimposed on the basic magnetic field
Implementation Method 2
To trigger nuclear magnetic resonances that can be measured as signals, radio-frequency excitation pulses (RF pulses) are irradiated into the object for examination
Implementation Method 3
as their T2* time, the effective decay of the transverse magnetization of this substance or tissue, is significantly shorter than the shortest possible echo times
Data Source
AI summary
A method for creating measurement data of an object for examination located in a measurement volume of a magnetic resonance system, including: a) increasing a gradient until it has reached a first strength in an encoding direction; b) irradiating an RF excitation pulse while the gradient has the first strength; c) after the end of the RF excitation pulse, reducing the strength of the gradient; d) increasing the gradient again until it has reached a desired strength in the encoding direction; and e) recording MR signals generated by the RF excitation pulse as measurement data along a k-space trajectory specified by the gradient present during the recording and storing this measurement data in a measurement data set, the gradient having the desired strength during the recording of the measurement data.