Accelerated MR Imaging via Under-Sampled Echo-Planar Trajectory
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Solution Overview
Problem
The time resolution in M-mode MRI is limited by the extensive duration of 2D excitation pulses, and while parallel excitation can address this, it requires extensive setup and is only available on a few scanners, necessitating a method to reduce pulse duration without this approach.
Innovation Solution
An MRI system using an under-sampled echo-planar excitation trajectory to excite multiple pencil regions simultaneously with multiple coils, and employing parallel imaging reconstruction to separate contributions from these regions, thereby reducing the duration of 2D excitation pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 2D excitation pulses are used in M-mode MRI, then spatial encoding is achieved, but time resolution is limited due to extensive pulse duration
Solution Approach 1:
The imaging space is segmented into multiple pencil regions that are excited simultaneously using an under-sampled echo-planar excitation trajectory. This segmentation allows the total imaging task to be divided into multiple smaller regions, each contributing to the overall image data, thereby reducing the time required for each individual excitation pulse while maintaining complete spatial coverage through the multi-region approach
Solution Approach 2:
The patent transitions from conventional single-region excitation to multi-region simultaneous excitation by introducing an additional spatial dimension in the excitation pattern. The under-sampled echo-planar trajectory excites multiple pencil regions along the phase-encoding direction at the same time, effectively adding a temporal dimension to the excitation process and reducing overall scan time while maintaining image quality through parallel imaging reconstruction
2Measurement precision
If parallel excitation architecture is used to reduce pulse duration, then time resolution improves, but device complexity increases due to extensive setup requirements
Solution Approach 1:
The patent makes a single transmit coil perform multiple functions by using it to simultaneously excite multiple pencil regions through the under-sampled echo-planar trajectory. This multi-functional approach eliminates the need for multiple independent transmit elements and drivers, achieving the benefits of parallel excitation with a single coil system, thereby reducing device complexity while maintaining improved time resolution
Solution Approach 2:
Instead of using multiple physical transmit coils, the patent creates virtual copies of the excitation process by applying the under-sampled echo-planar trajectory to a single coil. This copying approach generates multiple excited regions from one physical coil, achieving parallel excitation effects without the hardware complexity of true parallel excitation systems
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 method significantly reduces the duration of 2D excitation pulses, improving time resolution and enabling simultaneous imaging from multiple regions, which aids in applications like respiratory navigation and velocity-encoded M-mode MRI without the need for parallel excitation.
Implementation Method 1
an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly comprising at least one RF transmit coil
Implementation Method 2
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field
Implementation Method 3
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used
Implementation Method 4
A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image
Data Source
AI summary
A system and method for accelerated MR imaging includes a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly comprising at least one RF transmit coil and comprising multiple coils to acquire MR images. The MRI apparatus also has a computer programmed to excite multiple pencil regions by use of an under-sampled echo-planar excitation trajectory and acquire MR signals simultaneously on multiple channels of the RF coil assembly. The computer is also programmed to separate contributions from the various multiple pencil regions by use of parallel imaging reconstruction.