MRI Frequency Drift Correction via Embedded Volumetric Navigators
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in accurately measuring resonance frequency drifts caused by high gradient duty cycles and subject motion without increasing scan time, as existing methods require additional scan time for frequency and shim correction.
Innovation Solution
A method that estimates frequency-drift errors by acquiring multiple echo signals during each repetition time period, using echo-planar imaging (EPI) pulse sequences with embedded volumetric navigators, and computing phase offset values to determine frequency drift, allowing for real-time correction without extending scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If paired volumetric navigators with shifted echo times are used for frequency and shim correction, then frequency drift measurement accuracy is improved, but scan time increases
Solution Approach 1:
The patent extracts the frequency drift measurement function from the traditional paired vNav approach and implements it within a single vNav acquisition. By selecting reference data from the first TR period and comparing subsequent TR data against this reference, the system obtains frequency drift information without requiring additional navigator acquisitions, thus eliminating the time penalty of paired vNavs.
Solution Approach 2:
The patent makes the single volumetric navigator serve multiple functions: it simultaneously performs motion tracking and frequency drift measurement. By computing phase offset values from the navigator data across different TR periods, the system extracts both motion information and frequency drift information from the same data acquisition, eliminating the need for separate frequency correction scans.
2Measurement precision
If additional frequency correction sequences are implemented, then frequency drift correction accuracy is improved, but productivity decreases
Solution Approach 1:
The patent merges frequency drift measurement and correction functionality into the existing single vNav acquisition sequence. By computing phase offset values from the navigator data and using these to correct frequency drift in the main imaging data, the system combines multiple correction functions into one integrated process, maintaining accuracy while improving scan efficiency.
Solution Approach 2:
The system uses its own navigator data to perform frequency drift correction. The phase offset values computed from the vNav signals are directly applied to correct frequency drift in the imaging data, making the system self-correcting without requiring external reference scans or additional correction sequences.
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 enables efficient and accurate real-time frequency drift correction, improving motion correction quality and reducing artificial motion artifacts in MRI scans.
Implementation Method 1
a method for estimating frequency drifts in a magnetic resonance signal acquired with a magnetic resonance imaging (MRI) system
Data Source
AI summary
Systems and methods for estimating frequency drifts in magnetic resonance signals acquired with a magnetic resonance imaging (“MRI”) system are provided. In one example, the frequency drifts are estimated from phase-correction data that are obtained during an echo-planar imaging (“EPI”), or other multiecho imaging, scan. The systems and methods of the present invention provide for efficiently and accurately computing frequency drift values that can be used for real-time, prospective frequency drift correction.