MRI Center-Frequency Correction With Camera-Based Motion Tracking
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Solution Overview
Problem
Existing methods struggle to accurately separate phase changes caused by variations in the center frequency from those caused by body motion in magnetic resonance imaging, leading to misregistration in MRI images, especially when body motions are abrupt or periodic.
Innovation Solution
Combining navigator echoes with optical means, such as a surveillance camera, to detect body motion and use body motion information to determine the influence of body motion on phase changes, allowing for accurate separation and correction of center frequency variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If navigator echo is used to detect phase change for center frequency variation correction, then measurement precision of phase change is improved, but the presence of body motion makes it difficult to accurately separate phase change caused by center frequency variation from phase change caused by body motion
Solution Approach 1:
A camera is introduced as an intermediary device to detect body motion separately from the MRI scanner. The camera captures images of the subject's body, and the detected body motion information is fed back to the MRI system to compensate for the phase changes caused by body motion, thereby enabling accurate separation of center frequency variation from body motion effects
Solution Approach 2:
The patent replaces the reliance on purely MRI-based phase detection with a hybrid approach that uses optical detection (camera) to monitor body motion. This substitution of mechanical/optical detection for purely electromagnetic detection enables external monitoring of body motion that would otherwise be indistinguishable from center frequency variations in the MRI signal
2Measurement precision
If phase change is calculated from navigator echo, then center frequency variation can be detected, but abrupt or large body motion makes it difficult to calculate phase change accurately
Solution Approach 1:
The system continuously monitors body motion using the camera and feeds this information back to the MRI processing system. Based on this feedback, the system dynamically adjusts the phase change calculation by excluding time periods when abrupt body motion is detected, thereby maintaining reliable center frequency variation measurement even in the presence of motion
Solution Approach 2:
The system performs preliminary detection of body motion using the camera before and during the MRI scanning process. By identifying periods of abrupt body motion in advance, the system can preemptively exclude these periods from phase change calculations, preventing inaccurate measurements before they occur
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 precise correction of center frequency variations while accounting for body motion, resulting in high-quality MRI images by eliminating the influence of body motion and ensuring accurate frequency variation correction.
Implementation Method 1
generates nuclear magnetic resonance in the atomic nuclei of the atoms that constitute the tissue of an examination target (subject), collects nuclear magnetic resonance signals generated as a result
Implementation Method 2
generates a navigator echo for detecting a phase change separately from an echo for image formation (nuclear magnetic resonance signal) and calculates the phase change using the navigator echo
Data Source
AI summary
In a case where misregistration caused by variations in a center frequency is corrected using an amount of phase change calculated using a navigator echo, an influence of a body motion included in the amount of phase change is eliminated to improve accuracy of the correction.Calculation of a correction value for correcting variations in a center frequency is adjusted while referring to body motion information obtained by detecting a body motion of a subject during an examination. The adjustment is performed using methods such as performing only body motion correction without performing correction while a large body motion occurs, estimating the correction value from a change in a correction value calculated in a case where there is no body motion, or correcting the correction value based on the body motion information.