MRI Apparatus Dynamic Flip Angle Sweep for Multi-Contrast Imaging
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Solution Overview
Problem
The Variable Flip Angle (VFA) method for MRI is inefficient in acquiring MR images with different contrasts in a shorter imaging time, leading to prolonged imaging sessions due to the need for multiple sweep patterns of flip angles, which increases the overall imaging time.
Innovation Solution
A magnetic resonance imaging apparatus and method that utilizes a data acquiring unit to acquire signal trains with changing flip angles following an excitation pulse, and an image generating unit to generate frames of image data with different contrasts based on optimized sweep patterns of flip angles, allowing for the acquisition of images with varying contrasts in a single scan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple sweep patterns of flip angles are used to acquire images with different contrasts, then image quality is improved, but imaging time becomes longer
Solution Approach 1:
The patent combines multiple sweep patterns of flip angles into a single integrated sequence. The system performs T1-weighted imaging and T2-weighted imaging within one scan by varying the flip angle according to a predetermined pattern that includes both T1-appropriate angles (10-30 degrees) and T2-appropriate angles (60-90 degrees), thereby acquiring multiple contrast images simultaneously without requiring separate scans for each contrast type.
Solution Approach 2:
The patent employs dynamic variation of the flip angle during the imaging sequence. Instead of using a fixed flip angle, the system dynamically adjusts the flip angle according to a predetermined sweep pattern that changes over time, allowing optimization for different tissue contrasts (T1 and T2 weighting) within a single sequence. This dynamic adjustment enables the system to adaptively optimize image contrast while maintaining efficient imaging timing.
2Manufacturing precision
If the number of slices is increased to achieve isotropic pixels, then image resolution is improved, but imaging time becomes longer
Solution Approach 1:
The patent changes the flip angle parameter dynamically during the imaging sequence to optimize signal characteristics for different slice positions and contrasts. By varying the flip angle according to a predetermined sweep pattern, the system maintains signal intensity and image quality across multiple slices without requiring an excessive number of slices, thereby achieving isotropic or near-isotropic resolution more efficiently.
Solution Approach 2:
The patent implements continuous signal acquisition throughout the imaging sequence by maintaining coherent echo train formation. The system continuously collects MR signals across all slices throughout the duration of the sequence, rather than sequentially acquiring each slice separately. This continuous acquisition approach maintains high spatial resolution across multiple slices while minimizing the total imaging time.
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 the acquisition of MR images with improved image qualities and reduced imaging time by optimizing the sweep pattern of flip angles, allowing for the generation of frames with different contrasts efficiently, thus shortening the overall imaging process.
Implementation Method 1
a static magnetic field magnet 21 for generating a static magnetic field
Implementation Method 2
an RF coil 24 for transmitting and receiving a RF signal
Implementation Method 3
a gradient coil 23 for generating gradient magnetic fields
Implementation Method 4
magnetic resonance imaging (MRI) which magnetically excites nuclear spin of an object set in a static magnetic field with a RF (radio frequency) signal having the Larmor frequency and reconstructs an image based on MR (magnetic resonance) signals generated due to the excitation
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes a data acquiring unit and an image generating unit. The data acquiring unit is configured to acquire a signal train of magnetic resonance signals from an object by a spin echo method for applying a refocus pulse repeatedly following an excitation pulse with changing a flip angle of the refocus pulse. The image generating unit is configured to generate frames of image data having different contrasts, based on different portions of the signal train of the magnetic resonance signals.