MRI Phase Offset Determination Using Multi-Echo Subtraction
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Solution Overview
Problem
Current methods for determining phase offsets in Magnetic Resonance Imaging (MRI) are inefficient and inaccurate, often requiring additional volume coils or coarse estimations, which are not feasible in ultra-high field scanners and result in poor phase matching and high computational costs.
Innovation Solution
A method that involves acquiring two images at specific echo times with a chosen ratio, generating a phase evolution image, and subtracting an n-fold of this image from the first phase image to determine phase offsets without unwrapping, allowing for efficient and accurate phase offset correction without additional reference coils or complex computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional body coil or reference coil is used for phase offset determination, then phase offset measurement accuracy is improved, but device complexity and space requirements increase
Solution Approach 1:
The receiver coils in the array determine phase offsets using only their own acquired images and signals, without requiring external reference coils. Each coil independently calculates its phase offset by comparing images at different echo times, making the system self-sufficient and eliminating the need for additional hardware
Solution Approach 2:
The phase offset determination function is extracted from the traditional reference coil approach and integrated directly into the receiver coil signal processing. The unwanted reference coil hardware is removed while retaining the essential phase offset measurement capability through mathematical operations on existing signals
2Ease of manufacture
If traditional phase offset determination methods are used, then phase offset can be roughly estimated, but manufacturing precision and phase matching quality deteriorate
Solution Approach 1:
Images are acquired at multiple predetermined echo times before final phase image generation. This preliminary acquisition of multi-echo images enables accurate phase offset determination through subsequent calculation, ensuring high phase matching precision in the final combined phase image
Solution Approach 2:
The mechanical/physical reference coil system is replaced with a computational approach. Phase offsets are determined through mathematical operations on complex image data from multiple echo times, substituting hardware-based reference with software-based calculation to achieve superior precision
3Measurement precision
If additional reference coils are deployed, then phase offset determination is possible, but loss of time and acquisition duration increase
Solution Approach 1:
Phase offset determination is merged with the routine image acquisition process. The same receiver coils used for diagnostic imaging are utilized to determine phase offsets, and images at multiple echo times are acquired as part of the standard protocol, eliminating the need for separate reference coil measurements and reducing total acquisition time
Data Source
AI summary
The disclosed subject matter relates to a method for determining phase offsets in a complex-valued image in Magnetic Resonance Imaging, including the steps of,immobilising an object and acquiring a first image thereof at a predetermined first echo time and a second image thereof at a predetermined second echo time, the first and second images being separated into first and second magnitude images and first and second phase images, respectively, wherein a ratio between said first echo time and said second echo time is chosen to be n:(n+1), n being a positive integer;generating, pixel by pixel, a phase evolution image; andsubtracting, pixel by pixel, an n-fold of the phase evolution image from the first phase image to obtain a phase offset image containing said phase offsets.