Color-Coded Position Sensing for MRI-Compatible Imaging Tables
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Solution Overview
Problem
Existing encoders for medical imaging systems, particularly those combining PET and MRI, face challenges in achieving high accuracy, MRI compatibility, and cost-effectiveness for PET signal attenuation correction, with issues such as contamination, mechanical slip, and interference from magnetic fields.
Innovation Solution
A position determination system using a reference arrangement with color-coded bands and a sensor unit to detect absolute positions, employing color sensors and a microcontroller for precise, MRI-compatible, and cost-effective position, speed, and direction measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical encoders with glass rod and LED are used to achieve high position accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical encoders (optical or magnetic) with a camera-based vision system that uses image processing to determine the position of the support table. Instead of using physical scales, LEDs, or magnetic bands, the system captures images with a camera and calculates position from the image data, thereby eliminating complex mechanical components while maintaining measurement capability.
Solution Approach 2:
The patent uses an optical copy (image) of the support table's position markers as detected by the camera to determine actual position. Rather than directly measuring position through physical contact or proximity sensors, the system creates an optical replica of the position information through imaging and processes this copy to extract position data.
2Ease of manufacture
If incremental encoders are used for position detection, then ease of implementation is improved, but reliability deteriorates due to need for zero-point calibration
Solution Approach 1:
The patent incorporates position markers that are pre-defined and pre-calibrated in the system design. The support table has markers at known positions, and the camera system is configured to recognize these markers and their expected locations. This preliminary setup eliminates the need for runtime zero-point calibration, as the reference positions are established beforehand through the marker design.
Solution Approach 2:
The system uses the support table's own markers as reference points for position determination. The markers are attached to or integrated with the support table itself, allowing the table to serve as its own reference standard. This self-referencing approach eliminates dependency on external calibration systems or zero-point references, improving reliability while maintaining simplicity.
3Measurement precision
If magnetic encoders are used to achieve high position accuracy, then measurement precision is improved, but adaptability deteriorates due to MRI field interference
Solution Approach 1:
The patent replaces magnetic field-based sensing with optical field-based sensing (camera imaging). Since optical fields are not affected by magnetic fields, the system can operate in MRI environments without interference. The camera captures images using visible or near-visible light, which passes through or around the MRI magnet bore without being distorted by the strong magnetic field.
Solution Approach 2:
The patent introduces optical elements (camera, lenses, position markers with high-contrast patterns) as intermediaries to transfer position information from the support table to the control system. These optical intermediaries are immune to magnetic field interference, allowing position data to be transmitted accurately through the MRI environment without direct magnetic sensing.
4Ease of manufacture
If OLM encoders are used for position detection, then ease of manufacture is improved, but reliability deteriorates due to contamination
Solution Approach 1:
The patent replaces contact-based or proximity-based optical sensing (OLM encoders requiring close spacing) with a vision system that can detect position markers from a distance. The camera-based system does not require the sensor to be in close proximity to the measurement target, eliminating the risk of contamination from mechanical contact or close spacing, while maintaining ease of implementation through standard camera technology.
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 accurate, long-lasting, and inexpensive position determination suitable for PET attenuation correction, with no need for a zero-point calibration and resistance to electromagnetic interference, suitable for PET/MRI systems.
Implementation Method 1
a light source (53), which is embodied to illuminate reference colors of the reference arrangement arranged at the position of the sensor head
Data Source
AI summary
A position determination system for detecting a position of an object, wherein the position determination system comprises: a reference arrangement with reference colors with a first color code extending in a direction of a path of movement of the object, wherein along the path of movement, the first color code has color-differentiated and non-repeating discrete color sections as reference colors; a sensor unit with a sensor head, the sensor unit configured to read out the reference colors of the reference arrangement arranged at a position of the sensor head and to forward the read out reference colors to an evaluation unit; and at least one light source configured to illuminate the reference colors of the reference arrangement arranged at the position of the sensor head.