3D bSSFP Pulse Sequence for Arterial Spin Labeling MRI
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in acquiring high-definition arterial spin labeling (ASL) images in a short period of time, particularly due to limitations in pulse sequence design which affect image quality and acquisition time.
Innovation Solution
A magnetic resonance imaging apparatus utilizing a 3D balanced steady-state free precession (bSSFP) sequence to generate ASL images by applying RF pulses and gradient magnetic fields, with subsampling during transient and steady-state periods, and employing parallel imaging to process the data efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional pulse sequences are used for ASL imaging, then image quality can be maintained, but acquisition time becomes excessively long
Solution Approach 1:
The patent changes the fundamental parameters of the pulse sequence by using 3D bSSFP instead of conventional 2D sequences, modifying the imaging approach from slice-by-slice to volumetric acquisition. This parameter change enables simultaneous acquisition of multiple slices, dramatically reducing acquisition time while maintaining image quality through the inherent high signal-to-noise ratio of 3D bSSFP
Solution Approach 2:
The patent transitions from 2D slice-based imaging to 3D volumetric imaging by applying RF pulses and gradient fields in three dimensions. This dimensional change allows parallel acquisition of data from multiple slices simultaneously, resolving the contradiction between fast acquisition and image quality by acquiring the entire volume in a single sequence
2Productivity
If 3D bSSFP sequence is used to reduce acquisition time, then productivity improves, but device complexity increases
Solution Approach 1:
The patent employs periodic RF pulsing with specific timing patterns characteristic of bSSFP sequences, where RF pulses are applied periodically to maintain steady-state magnetization. This periodic action enables rapid data acquisition while the balanced gradient design simplifies the overall sequence structure, offsetting the inherent complexity of 3D imaging
Solution Approach 2:
The bSSFP sequence maintains continuous signal acquisition throughout the imaging process without repeated excitation cycles required by conventional sequences. This continuity of useful action eliminates idle time between excitations and allows uninterrupted data collection, improving productivity while the steady-state nature of the sequence actually reduces computational complexity compared to repeated excitations
3Productivity
If subsampling is applied during transient and steady-state periods, then data acquisition efficiency improves, but measurement precision may be affected
Solution Approach 1:
The patent applies subsampling during the transient period before the steady-state is fully established, capturing data when the magnetization is already evolving toward the steady-state value. This preliminary action allows efficient data acquisition with reduced measurements while the subsequent steady-state data provides the accurate reference values, resolving the contradiction between efficiency and precision
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 rapid acquisition of high-definition ASL images by optimizing the pulse sequence and data processing, thereby improving image quality and reducing acquisition time.
Implementation Method 1
Magnetic resonance imaging apparatus configured to generate an arterial spin labeling (ASL) image, using a 3D balanced steady-state free precession (bSSFP) sequence
Data Source
AI summary
A magnetic resonance imaging apparatus includes a signal transceiver, and a sequence controller configured to control the signal transceiver to apply an RF pulse and a gradient magnetic field to a first portion of an object, wait for blood to flow from the first portion of the object to which the RF pulse and the gradient magnetic field are applied, to a second portion of the object, and apply the RF pulse and the gradient magnetic field to the second portion of the object to which the blood flows, using a 3D balanced steady-state free precession (bSSFP), and subsample first magnetic resonance data from the second portion of the object to which the RF pulse and the gradient magnetic field are applied. The apparatus further includes an image processor configured to generate label image data based on the first magnetic resonance data.