X-ray Phantom Calibration Using Planar Mirror and Single Camera
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Solution Overview
Problem
Current calibration methods for X-ray diagnostic systems using position detection systems and phantoms suffer from inaccuracies due to the need for multiple measurements, which increase errors as the angle between the phantom and cameras decreases or the distance between the acquisition unit and phantom increases.
Innovation Solution
A calibration system where the X-ray phantom is positioned and oriented relative to the acquisition unit of the position detection system, allowing for minimal X-ray projection images to be taken, and using a single camera with a planar mirror to detect the marker configuration, reducing the need for multiple measurements and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are taken to determine the position of the X-ray phantom and X-ray beam receiver, then the coordinate transformation can be calculated, but the measurement accuracy decreases due to accumulated errors
Solution Approach 1:
The patent combines the X-ray phantom and position detection system into a single integrated calibration device. The phantom is rigidly connected to the acquisition unit, eliminating the need for separate position measurements of both components. This merging reduces the number of measurements from multiple separate measurements to a single coordinated measurement, thereby reducing accumulated errors and improving coordinate transformation accuracy.
Solution Approach 2:
The patent introduces a planar mirror as an intermediary element in the optical path of the position detection system. The mirror enables a single camera to capture marker positions from multiple angles or positions, effectively replacing the need for multiple cameras or repeated measurements. This intermediary allows the system to obtain sufficient calibration data with fewer measurements, reducing error accumulation.
2Measurement precision
If the angle between the X-ray phantom and camera entrance pupils is small, then the device can be more compact, but the coordinate system error increases
Solution Approach 1:
The patent uses a planar mirror to redirect the optical path, effectively adding a spatial dimension to the measurement geometry. By reflecting light at specific angles, the mirror enables the camera to view markers from optimized angles without requiring the camera to be physically positioned at large distances or angles. This dimensional manipulation of the optical path maintains accurate coordinate measurement while allowing for a more compact physical device layout.
3Measurement precision
If the distance between the acquisition unit and X-ray phantom is large, then the field of view is improved, but the coordinate system error increases
Solution Approach 1:
The planar mirror creates a virtual image (optical copy) of the marker configuration at a different apparent position and orientation. This virtual copy allows the camera to measure marker positions as if they were at an optimal distance and angle, without requiring the physical phantom to be positioned far from the acquisition unit. The mirror effectively copies the spatial relationships needed for accurate calibration while maintaining a compact physical configuration.
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 approach improves the accuracy of the calibration by allowing the X-ray phantom to be reproducibly positioned and reducing errors in coordinate transformation calculations, enhancing the precision of the X-ray diagnostic system's navigation.
Implementation Method 1
a single camera with a planar mirror to detect the marker configuration
Implementation Method 2
an X-ray source and an X-ray beam receiver... When the X-ray source is actuated, X-rays are emitted from a focal spot and propagate to an entrance window of the X-ray beam receiver
Data Source
AI summary
The subject matter of the present application relates to methods for calibrating an X-ray diagnostic system and apparatus for use in the calibration methods. In one embodiment, the apparatus includes a position detection system having an acquisition unit. An X-ray phantom is disposed near the acquisition unit in a known position and/or orientation relative to a coordinate system of the position detection system. The X-ray phantom may be detachably mounted on the acquisition unit.