MR Data Acquisition With RF Pulse Correction for Short T2* Signals
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Solution Overview
Problem
Conventional magnetic resonance (MR) methods struggle to acquire data from substances with very short T2* times due to echo time limitations, leading to artifacts and restricted excitation possibilities, particularly in radial acquisition methods with interscan delay.
Innovation Solution
An optimized method for determining and adjusting RF excitation pulse parameters and imaging parameters to correct undesired slice selectivity, allowing for improved acquisition of data from substances with short T2* times, using a magnetic resonance system with an optimization unit to automatically adjust parameters based on desired imaging protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional (T) SE or GRE sequences are used, then the acquisition method is simple and well-established, but substances with T2* times below 500 μs cannot be acquired because the signal has already decayed by the time of acquisition
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the echo time parameter to achieve ultrashort echo times (TE < 500 μs). This is accomplished through a radial acquisition trajectory that passes through the k-space center, combined with specific gradient switching sequences that enable signal acquisition before T2* decay eliminates the signal. The parameter change from conventional Cartesian sampling to radial sampling is the key enabler for capturing signals from substances with very short T2* times.
2Reliability
If radial acquisition with interscan delay is used to achieve ultrashort echo times, then substances with short T2* times can be acquired, but undesired slice selectivity disturbances occur due to gradient switching during RF excitation pulses
Solution Approach 1:
The patent applies preliminary anti-action by implementing a correction mechanism that anticipates and compensates for slice selectivity disturbances before they manifest in the final image. The system calculates expected disturbance patterns based on the known gradient switching sequence and RF pulse characteristics, then applies pre-computed correction factors to the acquired k-space data. This preliminary correction approach prevents the harmful effects from appearing in the reconstructed image, while maintaining the ability to acquire signals from substances with very short T2* times.
3Productivity
If gradient strength is increased to improve spatial resolution and reduce echo time, then acquisition speed improves, but slice selectivity disturbances are amplified
Solution Approach 1:
The patent applies feedback by implementing a closed-loop system that monitors the relationship between gradient strength and resulting slice selectivity disturbances. The system uses the quantification value (calculated from desired imaging parameters including readout bandwidth, resolution, and matrix size) to determine the expected disturbance level, then adjusts the correction magnitude accordingly. This feedback mechanism allows the system to maintain high gradient strengths for fast acquisition while dynamically adjusting correction parameters to compensate for the amplified disturbances, thereby preserving both acquisition speed and image quality.
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
Enables artifact-free acquisition of MR data from substances with short T2* times by optimizing RF excitation pulses and imaging parameters, facilitating correction of slice selectivity issues without user complexity.
Implementation Method 1
to trigger nuclear spin resonances measurable as signals, radio-frequency excitation pulses (RF pulses) are irradiated into the object under examination
Implementation Method 2
For position encoding of the measured data, rapidly switched magnetic gradient fields, called gradients for short, are superimposed on the constant magnetic field
Implementation Method 3
The magnetic alternating field generated by the excitation pulses irradiated by means of at least one transmit coil is also referred to as a B1 field
Data Source
AI summary
Techniques are described for acquiring data of an examination object and imaging parameters for an acquisition of measured data via an acquisition method in which gradients to be switched for position encoding of the measured data have their full strength during an irradiation of the RF excitation pulses, and a desired flip angle are loaded. The feasibility of the correction, the acquisition method is selectively performed with the loaded imaging parameters and the loaded flip angle. If a feasibility check is negative, a pulse duration of the RF excitation pulses to be irradiated in the acquisition method and/or of the desired flip angle are adjusted into an adjusted flip angle and/or at least one of the desired imaging parameters into an adjusted imaging parameter, and the acquisition method is performed with an adjusted pulse duration and/or with an adjusted flip angle and/or with an adjusted imaging parameter.