X-ray Calibration Using Geometric Feature Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for determining calibration information for X-ray devices in image-guided surgery are time-consuming and require complex setups, including visible markers and precise calibration objects, which are costly and not always necessary for accurate 3D X-ray scans.
Innovation Solution
A method that uses a 3D calibration data set created by scanning a calibration object with X-rays, allowing for the determination of calibration information through a calibration transformation between the X-ray device reference system and the 3D scan reference system, without the need for visible markers or precise calibration object shapes, using mathematical transformations and data processing to achieve accurate spatial relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If markers and precise calibration objects are used for calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the essential calibration function from complex marker-based systems. Instead of requiring markers on calibration objects, the system uses the natural geometric features detectable in X-ray images (edges, contours, spatial relationships) to perform calibration. This removes the unnecessary complexity of markers while maintaining calibration accuracy through mathematical transformation of detected geometric features.
Solution Approach 2:
The patent replaces expensive, precisely manufactured calibration objects with simple, cost-effective alternatives. The calibration object needs only to have detectable geometric features in X-ray images, not precise manufacturing tolerances or special markers. This dramatically reduces cost while maintaining sufficient calibration accuracy through computational methods.
2Measurement precision
If markers are required for calibration, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent removes the requirement for markers from calibration objects. Instead of manufacturing objects with attached markers, the system uses naturally detectable geometric features (edges, corners, contours) that any simple object with sufficient contrast will have in X-ray images. This makes manufacturing trivial while maintaining calibration capability through feature detection algorithms.
Solution Approach 2:
The patent changes the calibration approach from marker-based physical parameters to geometric feature-based parameters. Instead of relying on marker positions, the system detects edges, contours, and spatial relationships of geometric features in X-ray images, transforming the calibration problem into one that depends on image processing capabilities rather than manufacturing precision.
3Measurement precision
If pointers and markers are used for data entry, then navigation accuracy is improved, but time consumption increases
Solution Approach 1:
The patent implements self-service calibration where the system automatically detects geometric features of the calibration object in X-ray images and computes calibration parameters without manual intervention. The navigation system automatically identifies edges, contours, and spatial relationships, eliminating the need for operators to manually enter data with pointers while maintaining high accuracy through automated image processing.
Solution Approach 2:
The patent replaces manual mechanical pointer operations with automated optical/image-based detection. Instead of using physical pointers to input coordinates, the system uses X-ray image processing to automatically detect geometric features and compute positions, substituting mechanical data entry with computational image analysis that is both faster and equally accurate.
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
This method reduces the need for time-consuming data entry with pointers and allows for cost-effective calibration of X-ray devices, enabling precise spatial relationships for navigation in image-guided surgery without requiring visible markers or complex calibration object designs.
Implementation Method 1
A three-dimensional calibration data set is provided which describes a calibration object and is created by a three-dimensional scan with X-rays
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a method for determining calibration information, which includes information about a spatial relationship between an X-ray device reference system and a 3D scan reference system, wherein the determined calibration information can be used in particular for image-guided navigation, comprising the following steps: a 3D calibration data set is provided, which represents a three-dimensional calibration model of a calibration object in the 3D scan reference system, wherein the calibration model was determined from scan data generated by a calibration 3D X-ray scan, wherein in the calibration 3D X-ray scan an X-ray unit is moved along a 3D scan path relative to the calibration object, wherein at least a section of the 3D scan path is at rest in the X-ray device reference system;X-ray source relative position data are provided, which includes information about the relative position of an X-ray source relative to an X-ray unit marker device attached to the X-ray unit when producing real two-dimensional X-ray images; a 2D calibration dataset is provided, which describes a first of the real two-dimensional X-ray images produced by irradiating at least the calibration object at a first position (Fig. 1) of the X-ray source in the X-ray unit reference system, and which further a) describes a second of the real two-dimensional X-ray images produced by irradiating at least the calibration object, which is stationary relative to the first two-dimensional X-ray image, at a second position (Fig. 2) of the X-ray source in the X-ray unit reference system, and/or b) describes the dimensions of the calibration object;An X-ray unit dataset is provided that describes the position of the X-ray unit marker device during the generation of at least one real two-dimensional X-ray image; based on the X-ray source relative position data, the X-ray unit dataset, and the 2D calibration dataset, the calibration information is determined using an adjustment procedure.