MRI Apparatus Fat Signal Extraction via PASTA Sequence
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Solution Overview
Problem
Current magnetic resonance imaging techniques face challenges in effectively separating and quantifying signals of different types of fat, particularly olefinic fat, using single-voxel imaging and methods like IDEAL, which assume a single type of fat and struggle with high-resolution imaging in the presence of water signal absence or BO non-uniformity.
Innovation Solution
A magnetic resonance imaging apparatus employing a sequence controlling circuitry that executes a pulse sequence combining a Dixon-type preparation module with a Polarity Altered Spectral and Spatial Selective Acquisition (PASTA) scheme for 2D or 3D Fast Spin Echo, allowing for the extraction of multiple types of fat signals without complex algorithms, and enabling flexible adjustment of imaging parameters to stabilize image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IDEAL method is used to extract fat signals, then water and fat separation is achieved, but the method assumes only one type of fat and cannot quantify multiple fat types simultaneously
Solution Approach 1:
The patent segments the fat signal extraction process by performing separate acquisitions with different echo times (TE1 and TE2) and different frequency offsets (Δf1 and Δf2). This segmentation allows the system to isolate and quantify different fat types (saturated fat and olefinic fat) independently, resolving the limitation of IDEAL which can only handle one fat type at a time.
Solution Approach 2:
The patent adds temporal dimension by performing multiple acquisitions at different echo times and frequency offsets. This dimensional expansion transforms the single-point measurement limitation into a multi-dimensional data acquisition approach, enabling simultaneous quantification of multiple fat types through spectral decomposition.
2Measurement precision
If single-voxel MRS is used to quantify fat signals, then fat quantification is achieved, but 2D or 3D imaging capability is lost
Solution Approach 1:
The patent merges the advantages of single-voxel MRS (accurate fat quantification) with 2D/3D imaging capabilities by combining spectral selection with spatial encoding. The PASTA sequence integrates frequency-selective pulses for fat signal isolation with gradient echo train for spatial imaging, producing both quantitative fat maps and anatomical images simultaneously.
Solution Approach 2:
The patent creates a universal imaging method that performs multiple functions: it provides 2D/3D anatomical imaging, quantifies multiple fat types, and maintains water suppression capability. The PASTA sequence serves as a multi-functional tool that combines spectral imaging, chemical shift encoding, and spatial encoding in a single protocol.
3Measurement precision
If Dixon-type preparation is used for water-fat separation, then separation is achieved, but complex algorithms are required for multi-fat type extraction
Solution Approach 1:
The patent extracts the water and fat signals separately through frequency-selective acquisition. By using different frequency offsets (Δf1 for water, Δf2 for fat) in the two acquisitions, the system directly isolates the fat signal component without requiring complex iterative decomposition algorithms. This extraction approach simplifies the processing while maintaining separation quality.
Solution Approach 2:
The patent changes the frequency offset parameter between acquisitions to selectively capture water and fat signals. By setting Δf1 to center on water frequency and Δf2 to center on fat frequency, the system achieves water-fat separation through parameter variation rather than complex algorithmic decomposition, reducing computational complexity.
4Measurement precision
If receiver gain is adjusted for each acquisition, then signal optimization is achieved, but image quality consistency deteriorates
Solution Approach 1:
The patent performs preliminary optimization of receiver gain settings before the actual imaging acquisition. By pre-determining the optimal gain values for both acquisitions based on expected signal intensities, the system ensures consistent image quality across multiple acquisitions without requiring post-processing adjustment. This preliminary action prevents quality variations that would otherwise require complex normalization.
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 the extraction of multiple types of fat signals, achieving high-quality 2D or 3D images by maintaining consistent receiver gain and adjusting imaging parameters, thereby overcoming limitations of existing methods in resolving fat signals and water suppression.
Implementation Method 1
magnetic resonance imaging apparatus performs a first acquisition and a second acquisition by executing a pulse sequence
Implementation Method 2
applying an RF excitation pulse in presence of a gradient magnetic field, and subsequently applying an RF re-focusing pulse in presence of another gradient magnetic field
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes sequence controlling circuitry and processing circuitry. The sequence controlling circuitry performs a first acquisition and a second acquisition, the first acquisition including executing a preparation module corresponding to a first Echo Time (TE) value and subsequently performing an acquisition sequence, the second acquisition including executing the preparation module corresponding to a second TE value different from the first TE value and subsequently performing the acquisition sequence, the acquisition sequence being a pulse sequence including applying an RF excitation pulse in presence of a gradient magnetic field, and subsequently applying an RF re-focusing pulse in presence of another gradient magnetic field having an opposite polarity to that of the gradient magnetic field. The processing circuitry extracts at least one of a signal related to a first fat and a signal related to a second fat.