Hybrid 3D TSE MRI Acquisition for Time Utilization
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Solution Overview
Problem
In 3D turbo spin echo MRI sequences, the long repetition time (TR) results in significant waiting time due to spin magnetization saturation, leading to low time utilization and inefficiency in data acquisition, with existing methods failing to effectively utilize this waiting period without interfering with T1-recovery.
Innovation Solution
The proposed method incorporates two sub-echo-trains within each TR, where the first sub-echo-train is a turbo spin echo train with varied phase encoding and the second sub-echo-train is a gradient echo train, allowing simultaneous acquisition of two contrasts without interfering with T1-recovery, using low flip angle FLASH or trueFISP sequences to fill the waiting time with data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long repetition time (TR) is used in 3D turbo spin echo sequences to allow T1-recovery, then signal recovery is sufficient, but time utilization ratio becomes low due to significant waiting time
Solution Approach 1:
The patent applies continuous useful action by filling the waiting time between turbo spin echo trains with gradient echo data acquisition. Instead of leaving the system idle during the waiting period, gradient echo sequences are continuously acquired using low flip angles that do not significantly interfere with T1-recovery, thereby converting previously wasted time into productive data acquisition time and improving overall time utilization ratio
Solution Approach 2:
The patent segments the repetition time (TR) into two distinct parts: the first portion dedicated to turbo spin echo data acquisition with refocusing pulses, and the second portion (waiting time) utilized for gradient echo data acquisition. This segmentation allows both sequences to operate in parallel without significant interference, enabling efficient use of the entire TR period while maintaining signal recovery quality
2Productivity
If multiple refocusing RF pulses are applied to acquire multiple echoes, then more data can be acquired per excitation, but spin magnetization saturation occurs requiring longer TR
Solution Approach 1:
The patent applies partial action by using low flip angles (typically 10-30 degrees) for gradient echo excitation during the waiting time, which is insufficient to cause significant magnetization saturation. This partial excitation allows data acquisition without fully depleting the available magnetization, preserving the integrity of the T1-recovery process for the subsequent turbo spin echo train
3Manufacturing precision
If short echo train length is used to reduce image blurring, then signal decay is minimized, but time utilization ratio becomes low
Solution Approach 1:
The patent merges two different imaging sequences (turbo spin echo and gradient echo) into a single hybrid acquisition protocol. The turbo spin echo provides high-quality images with reduced blurring by using appropriate echo train lengths, while the gradient echo sequence fills the remaining time, combining the advantages of both sequences to achieve both high image quality and efficient time utilization
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 significantly increases the time utilization ratio by filling the waiting time with data acquisition, enabling simultaneous acquisition of two contrasts such as water and fat images, or turbo spin echo and susceptibility weighted images, while minimizing artifacts and maximizing signal-to-noise ratio.
Implementation Method 1
Magnetic resonance imaging employs temporally and spatially variable magnetic fields to encode position by affecting the local Larmor frequency of spins
Implementation Method 2
An MRI system typically establishes a homogenous magnetic field, generally along a central axis of a subject undergoing an MRI procedure
Implementation Method 3
Radio frequency fields are used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner
Implementation Method 4
the nuclei precess about the direction of the main magnetic field and emit electromagnetic signals that may be detected by one or more RF detector coils
Implementation Method 5
Gradient coils typically used for that purpose generate spatial encoding magnetic fields (=SEMs) which are superimposed on the main magnetic field
Implementation Method 6
If the orientation of the nuclear spins is perturbed out of alignment, the nuclei attempt to realign their spins with the field. During the realignment process, the nuclei precess about the direction of the main magnetic field
Data Source
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Figure 2a~3b
AI summary
A method for accelerating magnetic resonance imaging is suggested. In 3D MRI, it comprises two sub-echo-trains in each repetition time for the simultaneous acquisition of two contrasts. The first sub-echo-train is turbo spin echo train. The second sub-echo-train is gradient echo train. The invented method acquires two different contrasts simultaneously in a single acquisition, for example one water image plus one fat image, or one turbo spin echo image plus one susceptibility weighted image.