Retro-Grate Reflector Motion Tracking for MRI
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current medical imaging techniques, such as MRI, face challenges in accurately correcting for patient movement during long-duration scans due to limitations in motion tracking systems, particularly in maintaining calibration and accurately tracking motion in confined spaces like MR scanners, leading to motion artifacts and reduced image quality.
Innovation Solution
A motion tracking system using Retro-Grate Reflectors (RGRs) with a camera and mirrors to detect and correct for patient motion in real-time, allowing dynamic adjustment of scan parameters and incorporating motion filtering and prediction to enhance accuracy, while also enabling self-calibration and reducing the need for specialized calibration tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cameras are mounted outside the MR scanner bore using mirrors, then magnetic field interference is reduced, but the system complexity and calibration difficulty increase
Solution Approach 1:
The patent introduces mirrors as intermediary components that redirect light paths, allowing cameras to be positioned outside the MR scanner bore while maintaining line-of-sight to markers on the patient. This mediator approach enables magnetic field isolation while preserving optical tracking functionality.
Solution Approach 2:
The system transitions from direct linear camera-to-patient positioning to a multi-dimensional optical path using mirrors. By adding spatial dimensions through reflected light paths, the camera can be positioned in locations that would otherwise be inaccessible, reducing magnetic interference while maintaining tracking capability.
2Manufacturing precision
If scan duration is extended to increase resolution, then imaging detail improves, but patient motion artifacts increase
Solution Approach 1:
The system continuously monitors patient position using optical markers and cameras, providing real-time feedback about patient motion. This feedback loop enables dynamic adjustment of scan parameters or retrospective correction of motion artifacts, allowing long scans to maintain high resolution without compromising image accuracy.
Solution Approach 2:
The motion tracking system operates continuously throughout the scan, detecting patient position in advance of image acquisition. This preliminary detection of motion allows the system to predict and compensate for motion artifacts before they degrade image quality, preserving both resolution and accuracy.
3Measurement precision
If specialized calibration tools are used for motion tracking, then measurement accuracy improves, but the need for frequent recalibration increases
Solution Approach 1:
The system uses markers attached directly to the patient as self-calibrating reference points. These patient-specific markers automatically define the coordinate system, eliminating the need for external calibration tools and frequent recalibration procedures. The system calibrates itself using the patient's own anatomy as the reference.
Solution Approach 2:
The patent extracts the calibration function from separate specialized tools and integrates it directly into the patient setup process. By using markers attached to the patient rather than external calibration phantoms, the calibration process is embedded in the normal scanning procedure, eliminating dedicated recalibration steps.
4Measurement precision
If markers are placed on the patient for motion tracking, then motion detection accuracy improves, but the complexity of marker placement and attachment increases
Solution Approach 1:
The system uses visually distinct markers with high contrast against the patient's skin, making them easily detectable by the camera system. The markers' distinctive appearance simplifies automatic detection and tracking algorithms, reducing the complexity of processing despite the physical presence of multiple markers.
Solution Approach 2:
The patent transforms the marker placement process from a complex procedural task to a standardized parameter-based system. By defining specific anatomical locations for marker placement and using consistent marker designs, the system converts variable placement complexity into fixed, repeatable parameters that simplify both placement and processing.
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
The system provides high-accuracy, real-time motion correction with a potential time resolution in the millisecond range, significantly reducing motion artifacts and improving image quality, capable of correcting fast movements and maintaining accuracy over time without the need for frequent recalibration.
Implementation Method 1
an object orientation marker which is a Retro-Grate Reflector (RGR) that reflects light back toward the camera
Implementation Method 2
a mirror in a fixed position with respect to the scanner positioned so that the camera records repeated reflected images of the orientation marker in the mirror
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This invention relates to a system that adaptively compensates for subject motion in real-time in an imaging system. An object orientation marker (30), preferably a retro-grate reflector (RGR), is placed on the head or other body organ of interest of a patient (P) during a scan, such as an MRI scan. The marker (30) makes it possible to measure the six degrees of freedom (x, y, and z-translations, and pitch, yaw, and roll), or 'pose', required to track motion of the organ of interest. A detector, preferably a camera (40), observes the marker (30) and continuously extracts its pose. The pose from the camera (40) is sent to the scanner (120) via an RGR processing computer (50) and a scanner control and processing computer (100), allowing for continuous correction of scan planes and position (in real-time) for motion of the patient (P). This invention also provides for internal calibration and for co-registration over time of the scanner's and tracking system's reference frames to compensate for drift and other inaccuracies that may arise over time.