Spatial Registration for Imaging Devices Without Fiducial Markers
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Solution Overview
Problem
Existing medical imaging systems face challenges in precisely registering the location and orientation of a sensor with respect to the image plane of an imaging transducer, particularly in tracking instruments like needles during procedures, due to the arbitrary spatial position and orientation of the imaging position sensor relative to the image plane.
Innovation Solution
A method is developed to register the position and orientation of a tracking device on an imaging transducer using image processing techniques, involving the acquisition of images, identification of shapes and dimensions, calculation of spatial orientations, and transformation matrices to establish a constant spatial relation between the tracking device and the image plane, allowing precise registration without relying on internal or external fiducial markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is attached to the imaging transducer at an arbitrary location, then the device complexity is reduced and ease of operation is improved, but the measurement precision of the spatial position and orientation of the image plane deteriorates
Solution Approach 1:
The patent introduces a fiducial marker as an intermediary object that is attached to the imaging transducer. This marker serves as a mediator between the arbitrary position sensor location and the image plane, enabling precise spatial registration through image processing of the marker's known geometry without requiring complex direct sensor-to-image-plane calibration
Solution Approach 2:
The patent creates a virtual copy or representation of the fiducial marker's physical geometry in the digital image space. By processing the image of the marker and comparing it with its known physical dimensions and orientation, the system establishes the spatial transformation without requiring physical measurement instruments, thus reducing device complexity while maintaining precision
2Measurement precision
If fiducial markers are used for image registration, then the measurement precision of spatial registration is improved, but the ease of operation deteriorates due to the requirement of attaching and managing markers
Solution Approach 1:
The fiducial marker is designed to be self-identifiable through its unique geometric pattern. The image processing algorithm automatically detects and recognizes the marker's features (such as corners, lines, or specific shapes) without requiring manual intervention for marker identification or positioning, thereby maintaining ease of operation while achieving precise registration
Solution Approach 2:
The fiducial marker utilizes distinct visual characteristics (such as high-contrast patterns, specific colors, or geometric shapes) that make it easily distinguishable from the surrounding environment and patient anatomy. This visual distinctiveness enables automatic detection and robust recognition by the image processing system, simplifying the registration process while ensuring accurate spatial measurement
3Reliability
If the position sensor is placed away from the image plane for convenience, then the ease of operation is improved, but the reliability of tracking instruments relative to the image plane deteriorates
Solution Approach 1:
The patent replaces direct mechanical attachment of the position sensor to the image plane with an optical/image-based reference system. The fiducial marker attached near the sensor creates a visual reference that is captured by the imaging system, allowing the calculation of spatial relationships through image processing rather than direct mechanical coupling, thus maintaining reliability while improving ease of operation
Data Source
AI summary
A method is provided for registration of images obtained of a patient in real time with respect to a tracking device. The method is not based on internal or external fiducial markers attached to the patient, but rather the registration is done relative to a reference plate of a guiding system affixed to a table that supports the patient.