Liver MRI Multi-Parameter Mapping Using Joint Reconstruction
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Solution Overview
Problem
Conventional quantitative magnetic resonance imaging (MRI) methods for multi-parameter mapping of the liver are time-consuming and require multiple breath holds, limiting their use in clinical settings due to patient fatigue and potential position mismatch between quantitative parameters.
Innovation Solution
A modified echo-planar-imaging (EPI) sequence is used to acquire raw k-space data within one breath hold, processed using parallel imaging methods to estimate the inhomogeneous main magnetic field B0 map, and a joint reconstruction model is applied to obtain reconstructed images for simultaneous multi-parameter mapping of the liver, including T2 and T2* maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional quantitative imaging methods are used to acquire multiple different imaging sequences with different settings to estimate multiple quantitative parameters, then measurement precision is improved, but examination time increases significantly
Solution Approach 1:
The patent combines multiple imaging sequences (spin-echo and gradient-echo) into a single multi-echo EPI sequence that acquires all necessary signal types simultaneously at different echo times, eliminating the need for separate scans and reducing examination time while maintaining quantitative parameter accuracy
Solution Approach 2:
The multi-echo EPI sequence serves multiple functions by simultaneously acquiring T2-weighted signals, T2*-weighted signals, and phase information in a single scan, allowing estimation of multiple quantitative parameters (T2, T2*, B0 map) without requiring multiple dedicated sequences
2Measurement precision
If multiple separate scans are performed to acquire different quantitative parameters, then measurement precision is improved, but patient fatigue increases and position mismatch occurs
Solution Approach 1:
By merging multiple imaging sequences into a single multi-echo EPI acquisition, the patent eliminates repeated patient positioning and breath-holding requirements, reducing fatigue and preventing position mismatch between different quantitative parameter measurements
Solution Approach 2:
The patent performs all necessary signal acquisitions and quantitative parameter estimations during a single breath-hold period, completing the entire quantitative imaging protocol before the patient would experience fatigue or position changes that would occur with multiple separate scans
3Loss of time
If magnetic resonance fingerprinting is used to simultaneously quantify multiple MR parameters of one slice within a single breath hold, then examination time is reduced, but whole liver coverage requires multiple breath holds
Solution Approach 1:
The patent extends the single-breath-hold MRF approach from 2D slice-based acquisition to 3D whole-liver coverage by using multi-echo EPI with extended readout, allowing simultaneous quantification of multiple parameters across the entire liver in one breath-hold without requiring multiple separate breath-hold acquisitions
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 allows for rapid acquisition of comparable quantitative images within one breath hold, improving diagnostic efficiency and practical application value for evaluating liver damage and iron levels, while maintaining accuracy and robustness comparable to conventional methods.
Implementation Method 1
quantitative magnetic resonance imaging (MRI)
Implementation Method 2
modifying the echo-planar-imaging (EPI) sequence
Implementation Method 3
processing the raw k-space data by a parallel imaging method (such as SENSE or MUSSELS) to obtain images
Implementation Method 4
using the Bloch equation to form a dictionary that stores information about echo signals over time
Data Source
AI summary
The disclosure provides a modified EPI sequence for acquiring multi-shot and multi-echo images with interleaved blip-up and blip-down phase encoding; the blip-up and blip-down images are processed by topup in FSL to estimate the inhomogeneous main magnetic field B0 map that causes image distortions; the B0 map is then incorporated into the encoding matrix with a low rank constraint to form a joint reconstruction model; the joint reconstruction model is solved to obtain multiple distortion-free images; and the multiple distortion-free images are matched to dictionary to simultaneous acquire the quantitative T2(=1/R2) and T2*(=1/R2*) maps. In the phantom and in-vivo measurements, the disclosed method rapidly acquires the comparable quantitative images within one hold-breath (for 20 s) to the conventional mapping method, thus providing important practical application value for evaluation of liver damage, iron level and cancer lesion.