Optical Surface Detection for X-Ray Truncation Correction
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Solution Overview
Problem
X-ray computed tomography systems, particularly C-arm systems, face challenges in reconstructing three-dimensional images due to truncated projection images caused by parts of the object not being within the field of view, leading to image artifacts that existing correction methods cannot optimally address.
Innovation Solution
The method involves using an optical sensor to detect the surface of the object, creating a surface model to supplement missing image data, and applying assumptions about x-ray absorption properties to refine the reconstruction of truncated parts, allowing for improved truncation correction during image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a small x-ray detector is used in C-arm systems, then good access to the patient is achieved, but parts of the object are truncated in projection images causing image artifacts
Solution Approach 1:
An optical sensor is introduced as an intermediary device to detect the patient's surface geometry. This optical information serves as a mediator between the truncated x-ray projection images and the complete three-dimensional reconstruction, allowing the system to compensate for the limited detector size without compromising patient accessibility
Solution Approach 2:
The optical surface detection is performed before the x-ray reconstruction process to preliminarily capture the complete geometry of the patient's surface. This preliminary geometric information is then integrated during the reconstruction phase to supplement the truncated projection data, enabling accurate reconstruction despite the small detector size
2Reliability
If linear extrapolation is used to supplement truncated projection images, then image artifacts are reduced, but optimal correction is not achieved
Solution Approach 1:
The invention changes the parameter used for supplementation from simple intensity-based linear extrapolation to geometry-based optical surface detection. By using optical sensor data that captures actual surface geometry, the system transforms the supplementation approach from a mathematical approximation to a physically informed correction, achieving optimal artifact reduction
Solution Approach 2:
The invention substitutes the mechanical/mathematical approach of linear extrapolation with an optical detection system. Instead of relying on mathematical assumptions about intensity gradients, the system uses optical sensors to directly measure the patient's surface geometry, providing more accurate information for correcting truncated projections
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 effectively minimizes image artifacts by accurately determining the size and shape of truncated object parts and their x-ray absorption properties, enabling a more precise and efficient reconstruction of three-dimensional tomography images.
Implementation Method 1
the surface of the examined object, e.g. of the patient, is detected with the aid of an optical sensor
Implementation Method 2
standard x-ray images, which contain no depth information since they display a projection of a three-dimensional object on a two-dimensional plane
Implementation Method 3
the x-ray absorption properties of this part of the object
Data Source
AI summary
The invention relates to a method for “truncation correction” in an x-ray system, i.e. a correction method during the reconstruction of projection images of an object recorded from different projection angles, if parts of the object do not lie in the field of view of each projection image. The surface of the object is thereby optically detected and used during the reconstruction of projection images to supplement the missing image data.