Multi-slice T2 Mapping Interleaved Acquisition
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Solution Overview
Problem
Current T2-weighted MRI techniques require long scan times due to the need for rest periods between data acquisitions to allow for full signal recovery, resulting in inefficient data acquisition and longer scan times, especially for multi-slice and 3D T2 mapping sequences.
Innovation Solution
The implementation of a free-breathing multi-slice T2 mapping method that interleaves data acquisition of different slices during the recovery of specific slices, using slice-selective T2-preparation pulses to generate images with varying T2 weightings, allowing for simultaneous acquisition of multiple slices without waiting for magnetization recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rest periods are inserted between data acquisitions to allow for full signal recovery, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The imaging volume is divided into multiple slices that are acquired in an interleaved manner. While one slice is undergoing magnetization recovery, other slices are being imaged. This segmentation allows the system to maintain measurement precision for T2 mapping while eliminating idle rest periods, as different slices are processed in parallel during what would otherwise be waiting time.
Solution Approach 2:
The patent implements continuous data acquisition across multiple slices without inserting rest periods between acquisitions. By interleaving the imaging of different slices, the system ensures that useful action (data acquisition) continues uninterrupted, eliminating the time loss associated with traditional rest periods while maintaining the necessary magnetization recovery through parallel slice processing.
2Measurement precision
If multiple T2Prep samples are acquired for more precise T2 maps, then measurement precision is improved, but loss of time increases
Solution Approach 1:
Multiple T2Prep samples are acquired across different slices rather than sequentially in a single slice. The interleaved multi-slice approach allows the system to collect multiple T2-prepared images with different T2 values across multiple slices simultaneously, maintaining measurement precision and reproducibility while reducing the total acquisition time by parallelizing the sampling process.
3Measurement precision
If multi-slice imaging is performed with rest periods between acquisitions, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent eliminates rest periods between multi-slice acquisitions by implementing continuous interleaved imaging. Different slices are imaged in sequence without idle time, as each slice benefits from magnetization recovery occurring during the acquisition of other slices. This maintains T2-weighted image quality while dramatically improving data acquisition efficiency, achieving near 100% productivity compared to the 25% efficiency of traditional methods.
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 reduces scan time by eliminating the need for rest periods, improving data acquisition efficiency and enabling accurate, reproducible T2 mapping with a 20-heartbeat acquisition time for five left ventricular slices, comparable to single-slice sequences.
Implementation Method 1
When a substance such as human tissue is subjected to a uniform magnetic field, i.e., a static magnetic field B0, the individual magnetic moments of the excited nuclei in the tissue attempt to align with the static magnetic field B0, but precess about it in random order at their characteristic Larmor frequency. If the substance is subjected to a magnetic excitation field B1 that is in the x-y plane and that is near the Larmor frequency, the net magnetization aligned moment Mz may be rotated, i.e., tipped, into the x-y plane to generate a net transverse magnetic moment Mt. An MR signal is emitted by the excited nuclei, i.e., spins, after the excitation magnetic field B1 is terminated
Implementation Method 2
The T2 time constant is referred to as the spin-spin relaxation constant, or the transverse relaxation constant, and is characterized by a spin-spin relaxation time characterizing the signal decay. The T2 constant is inversely proportional to the exponential rate at which the aligned precession of the spins would dephase after removal of the excitation magnetic field B1 in a perfectly homogeneous magnetic field
Implementation Method 3
using slice-selective T2-preparation pulses to generate images with varying T2 weightings
Data Source
AI summary
An MRI method includes performing a first image acquisition module of a pulse sequence to acquire a first MR data from slices disposed at different locations in a region of interest (ROI) of an object; performing a second image acquisition module of the pulse sequence, to acquire a second MR data from the slices disposed at the different locations of the ROI, with a T2 preparation time different than that of the first image acquisition module; and generating a T2 map based on the acquired first MR data and the acquired second MR data.