Magnetic Resonance Fingerprinting with Gradient and Spin Echo Acquisition
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) methods for estimating T1, T2, and T2* parameters are limited by long acquisition times, making them unsuitable for routine clinical practice, and existing magnetic resonance fingerprinting (MRF) approaches struggle to accurately include T2* due to longer echo times and error propagation.
Innovation Solution
A method using a combined gradient echo and spin echo acquisition with integrated B1 correction, employing a series of variable sequence blocks with EPI readouts to simultaneously estimate T1, T2, and T2* parameters, reducing dictionary size and error propagation, and enabling faster acquisitions with higher SNR and fewer artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional qMRI methods are used to estimate T1, T2, and T2* parameters, then measurement precision is improved, but acquisition time increases significantly making them unfeasible for routine clinical practice
Solution Approach 1:
The patent divides the parameter estimation process into two separate segments: a first segment using gradient echo data for T1 and T2* estimation, and a second segment using spin echo data for T2 estimation. This segmentation allows each segment to be optimized independently and processed more efficiently, reducing overall acquisition time while maintaining measurement precision for all three parameters
Solution Approach 2:
The patent employs dynamic sequence blocks with varying parameters (TR, TE, FA) that change over time within each segment. This dynamic approach allows the sequence to adapt and optimize signal characteristics for different tissue types and parameter ranges, improving estimation accuracy while maintaining fast acquisition through efficient use of available time
2Adaptability or versatility
If T2* is included in MRF framework with longer TE, then T2* quantification capability is improved, but dictionary size increases and error propagation occurs
Solution Approach 1:
The patent separates T2* estimation (performed in the first segment using gradient echo data) from T2 estimation (performed in the second segment using spin echo data). This segmentation allows T2* to be quantified with appropriate longer TE values without requiring the dictionary to account for all possible T2 and T2* combinations, thereby reducing dictionary size and preventing error propagation between the two parameter estimations
Solution Approach 2:
The patent extracts T2* estimation from the traditional T2 estimation process by using separate gradient echo data in the first segment. This extraction allows T2* to be measured independently with optimized parameters, reducing the complexity and size of the dictionary required for simultaneous multi-parameter estimation
3Productivity
If gradient echo sequence is used for fast acquisition, then productivity is improved, but T2 estimation accuracy deteriorates
Solution Approach 1:
The patent merges gradient echo acquisition (first segment for fast T1 and T2* estimation) with spin echo acquisition (second segment for accurate T2 estimation) into a single unified sequence. This combination allows the benefits of fast gradient echo imaging to be paired with the superior T2 estimation capabilities of spin echo, achieving both high productivity and accurate T2 measurement
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 allows for faster and more accurate estimation of T1, T2, and T2* parameters, reducing acquisition time and dictionary size, while minimizing error propagation and image artifacts, facilitating more straightforward implementation and higher image quality.
Implementation Method 1
Magnetic resonance data are acquired from a subject by operating an MRI system to acquire the magnetic resonance data in a series of variable sequence blocks to cause one or more resonant species in the subject to simultaneously produce individual magnetic resonance signals
Implementation Method 2
data are acquired by sampling gradient echoes
Implementation Method 3
data are acquired by sampling spin echoes
Data Source
AI summary
Magnetic resonance fingerprinting (“MRF”) techniques in which T1, T2, and T2* are simultaneously quantified using a combined gradient echo and spin echo acquisition with integrated B1 correction are described. The values for T2 and T2* can be estimated separately, but using the same underlying dictionary. This approach enables a smaller dictionary size that is easily manageable, and also reduced error propagation. Moreover, by using echo planar imaging (“EPI”) readouts, the raw MRF images will have higher signal-to-noise ratio (“SNR”) relative images acquired using spiral-based MRF techniques. The EPI-based images are also relatively free of artifacts. Together, these advantages lead to the need for far fewer frames, thereby enabling much faster acquisitions. Moreover, offline reconstruction is not needed, allowing for a more straightforward implementation of MRF.