Fluoroscopic Registration Fixture for Flexible 2D-3D Navigation
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Solution Overview
Problem
The process of co-registering two-dimensional medical images with a three-dimensional tracking space is challenging due to the difficulty in constructing an accurate image volume from fluoroscopic images, especially with imaging artifacts, and planning trajectories differs from three-dimensional medical image volumes like CT scans.
Innovation Solution
A registration fixture is used with a surgical navigation system that includes a first and second ring with tracking markers, mounted to a fluoroscope, to facilitate co-registration by eliminating the need for fluoroscopic images at exactly 90 degrees and providing distortion correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluoroscopic images are used to construct a three-dimensional image volume for co-registration, then the process can be performed with available imaging equipment, but imaging artifacts and distortion reduce the accuracy of the constructed volume
Solution Approach 1:
A registration fixture with known geometry (rings with markers) is introduced as an intermediary object that appears in both the fluoroscopic images and the tracking space. This fixture serves as a mediator to establish the transformation between coordinate systems, allowing accurate co-registration despite the presence of imaging artifacts in the fluoroscopic images.
Solution Approach 2:
The system changes the approach from directly using distorted fluoroscopic image coordinates to using the known geometric parameters of the registration fixture. By relying on the pre-calibrated dimensions and marker positions of the fixture rather than the distorted image coordinates, the system achieves accurate co-registration.
2Measurement precision
If fluoroscopic images at exactly 90 degrees are required for accurate co-registration, then the registration accuracy is improved, but the operational flexibility and ease of positioning is reduced
Solution Approach 1:
The system transitions from a static requirement of exactly 90-degree imaging angles to a dynamic solution where the registration fixture can be viewed from any angle. The known geometry of the fixture allows the system to calculate the correct transformation parameters regardless of the fluoroscope's orientation, enabling flexible positioning during surgery.
Solution Approach 2:
The registration fixture serves multiple functions: it provides known geometric references for co-registration, works at various imaging angles, and can be used with different fluoroscope positions. This universal applicability eliminates the need for precise 90-degree positioning while maintaining registration accuracy.
3Measurement precision
If a registration fixture with spherical fiducials is used, then the fiducials are easily detectable, but the fixture design becomes more complex compared to simpler marker arrangements
Solution Approach 1:
Spherical fiducials are used on the registration fixture because their curved surfaces provide distinctive, easily detectable features in fluoroscopic images. The spherical shape creates characteristic projection patterns that simplify automated detection and reduce ambiguity in identifying fiducial positions, justifying the increased fixture complexity.
Data Source
AI summary
A registration fixture for use with a surgical navigation system for registration of a medical image or images to a three-dimensional tracking space that includes a first ring having at least one tracking marker, a second ring coupled to the first ring having at least one tracking marker and wherein the first ring and the second ring are spaced apart from one another and further include optical markers.