SPACE MRI Pulse Sequence for Aliasing-Free 3D Imaging
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Solution Overview
Problem
In magnetic resonance imaging, three-dimensional acquisition techniques face challenges with reduced flexibility and increased measurement time due to the need for complete data acquisition in all phase coding directions, often leading to aliasing artifacts and high specific absorption rate (SAR) issues.
Innovation Solution
A method using a spatially selective excitation pulse followed by a series of refocusing pulses with variable flip angles to acquire magnetic resonance data, limiting the excited region and reducing the need for extensive data acquisition, employing a SPACE sequence that allows for high-resolution 3D imaging in a shorter time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three-dimensional acquisition techniques are used to acquire magnetic resonance data in all phase coding directions, then aliasing artifacts are avoided, but measurement time is increased
Solution Approach 1:
The invention extracts and removes the aliased signal components from the image reconstruction process. By detecting aliasing artifacts and selectively eliminating them during image reconstruction, the method achieves high-quality images without requiring complete data acquisition in all phase coding directions, thereby reducing measurement time while maintaining image quality.
Solution Approach 2:
The invention changes the approach from acquiring complete data in all directions to acquiring reduced data and compensating through parameter adjustments in the reconstruction process. By modifying reconstruction parameters and using aliasing detection algorithms, the system achieves acceptable image quality with shorter measurement times.
2Reliability
If three-dimensional acquisition techniques are used to acquire magnetic resonance data in all phase coding directions, then aliasing artifacts are avoided, but flexibility in parameter adjustment is reduced
Solution Approach 1:
The invention introduces dynamic adaptability by detecting aliasing artifacts and adjusting reconstruction parameters accordingly. The system dynamically determines whether aliasing is present and adapts the reconstruction process to handle reduced data acquisition, thereby maintaining parameter flexibility while ensuring image quality.
3Reliability
If oversampling techniques are used to acquire additional data in phase coding direction, then aliasing artifacts are avoided, but measurement time is drastically increased and SAR limits are exceeded
Solution Approach 1:
The invention converts the harmful aliasing artifacts into useful information for reconstruction. Instead of avoiding aliasing through oversampling, the method deliberately allows aliasing to occur and then uses detection algorithms to identify and remove the aliased components, transforming a harmful effect into a manageable aspect of the acquisition process that enables faster scanning.
4Reliability
If oversampling techniques are used to acquire additional data in phase coding direction, then aliasing artifacts are avoided, but SAR limits are exceeded
Solution Approach 1:
The invention applies partial action by acquiring only the necessary minimum data required for image reconstruction rather than performing excessive oversampling. This selective data acquisition approach maintains image quality while staying within SAR limits by avoiding redundant measurements.
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 effectively avoids aliasing artifacts while reducing measurement time and SAR, enabling efficient acquisition of high-quality magnetic resonance data without the need for extensive data collection.
Implementation Method 1
the examination subject in a magnetic resonance apparatus is positioned in a strong, static, homogeneous basic magnetic field (called a B0 field) with a field strength of 0.2 to 7 Tesla or more, such that nuclear spins in the subject orient along the basic magnetic field. Radio-frequency excitation pulses (RF pulses) are radiated into the examination subject to trigger nuclear magnetic resonance signals
Implementation Method 2
After radiating the excitation pulse, a series of at least two refocusing pulses is radiated into the examination subject, which generate variable flip angles adapted to a predetermined signal curve
Implementation Method 3
Rapidly switched magnetic gradient fields are superimposed on the basic magnetic field for spatial coding of the measurement data
Data Source
AI summary
In a method and apparatus to acquire magnetic resonance data in a selected region of an examination subject without aliasing artifacts and with a reduced acquisition time, a spatially selective excitation pulse is radiated into the examination subject to excite nuclear spins in at least the selected region, and after radiating the excitation pulse, a series of at least two refocusing pulses is radiated into the examination subject, which generate variable flip angles adapted to a predetermined signal curve. At least the second refocusing pulse, and possibly every additional one of the refocusing pulses of this series, is a non-selective pulse. The spin echo signals generated by the refocusing pulses are acquired as magnetic resonance data. Gradients for spatial coding are activated before and after the spatially selective excitation pulse, the refocusing pulses and during the data acquisition. The acquired magnetic resonance data are stored and/or converted into image data for display.