Multiple-Echo MRI Pulse Sequence for Simultaneous T2* and Diffusion Measurement
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Solution Overview
Problem
Current methods for measuring T*2 and diffusion of hyperpolarized gas contrast agents in MRI require multiple breath-holds and are sensitive to lung inflation volume, limiting their repeatability and efficiency.
Innovation Solution
A multiple-echo projection acquisition based pulse sequence is employed to simultaneously measure T*2 and apparent diffusion coefficient (ADC) in a single breath-hold using a hyperpolarized gas contrast agent, allowing for isotropic resolution and reliable image registration by varying inter-echo spacing and diffusion weighting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple breath-holds are used to measure T*2 and diffusion, then measurement accuracy is improved, but examination time and complexity increase
Solution Approach 1:
The patent combines T*2 mapping and diffusion weighting into a single pulse sequence acquisition. By integrating both measurement capabilities into one breath-hold experiment, the method eliminates the need for multiple separate breath-holds while maintaining measurement accuracy through simultaneous acquisition of both parameters.
Solution Approach 2:
The pulse sequence is designed to perform multiple functions within a single acquisition: it simultaneously obtains T*2 information and diffusion-weighted signals. This multi-functional approach allows one breath-hold to serve multiple measurement purposes, reducing examination time without sacrificing precision.
2Reliability
If multiple breath-holds are used for measurement, then repeatability is improved, but device complexity and operational difficulty increase
Solution Approach 1:
By merging T*2 and diffusion measurements into a single pulse sequence execution, the method reduces operational complexity while maintaining repeatability. The unified sequence handles both measurements systematically in one breath-hold, eliminating the complexity of coordinating multiple separate acquisitions.
3Ease of operation
If conventional pulse sequences are used, then ease of operation is maintained, but measurement precision for simultaneous T*2 and diffusion is insufficient
Solution Approach 1:
The patent modifies pulse sequence parameters including variable echo times (TE) and diffusion weighting factors (b-values) to enable simultaneous T*2 and diffusion measurement. These parameter adjustments allow the sequence to distinguish between T*2 decay and diffusion effects while maintaining operational feasibility through systematic variation of acquisition parameters.
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 accurate and reliable simultaneous measurement of T*2 and ADC in a single breath-hold with a single dose of hyperpolarized gas, improving image quality and repeatability by separating diffusion and T*2 decay effects.
Implementation Method 1
the individual magnetic moments of the nuclei in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
The spin-warp scan technique employs a variable amplitude phase encoding magnetic field gradient pulse prior to the acquisition of MR spin-echo signals to phase encode spatial information in the direction of this gradient
Implementation Method 3
the sensitivity of MRI to the diffusion ofhyperpolarized gases within the lung microstructure provides a mechanism for assessing the viability of lung tissue
Data Source
AI summary
A method for measuring the apparent transverse relaxation time (“T*2”) and apparent diffusion coefficient (“ADC”) of a hyperpolarized gas in a single breath-hold and consequently, with a single dose of the hyperpolarized gas contrast agent, is provided. The method employs a multiple-echo projection acquisition based pulse sequence. Individual images are reconstructed from data acquired during each of the individual echo times. Subsequently, T*2 and ADC are calculated using these reconstructed images. Furthermore, the method produces images indicative of ADC that have isotropic resolution, allowing for more reliable image registration. The inter-echo spacing and diffusion weighting b-value are varied during the pulse sequence employed when practicing the present invention; thus, a significant separation between the effects of diffusion and T*2 decay on the detected MR signals is possible. This separation allows for reliable measurements of these two parameters from a single echo-train.