CT Gain Calibration via Projection Data Segmentation
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Solution Overview
Problem
Computed tomography (CT) systems face challenges in accurately calibrating measurements when the field of view is partially obstructed by objects, making it difficult to achieve uniform radiation exposure for detector arrays, which leads to errors in measurement correction.
Innovation Solution
A method and system for computing gain corrections using calibration procedures performed while the field of view is partially obstructed, separating calibration projection data from object projection data to correct for non-uniform exposure, allowing for accurate measurement correction during examinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed with clear line-of-sight (air scan), then measurement precision is improved, but device complexity and operation time increase due to requiring removal of all objects
Solution Approach 1:
The system performs calibration using the existing objects in the field of view rather than requiring removal of objects. The calibration procedure utilizes the actual examination conditions, allowing the system to self-calibrate without external intervention to clear the field of view.
Solution Approach 2:
The patent applies partial calibration action by performing calibration with objects present rather than requiring complete clearance. This partial approach (calibrating with objects in place) is sufficient to achieve acceptable measurement precision without the excessive action of removing all objects and performing full air scans.
2Ease of operation
If calibration is performed with objects in field of view, then ease of operation is improved, but measurement precision deteriorates due to non-uniform radiation exposure
Solution Approach 1:
The patent segments the projection data into two distinct components: calibration projection data (representing uniform radiation exposure) and object projection data (representing attenuation by objects). This segmentation allows separate processing of calibration information from object information, enabling accurate gain correction even when objects are present during calibration.
Solution Approach 2:
The patent introduces an intermediary processing step that identifies and separates calibration projection data from object projection data. This intermediary data separation acts as a mediator that allows calibration to be performed with objects present while still achieving uniform exposure correction, bridging the gap between ease of operation and measurement precision.
3Measurement precision
If air scan calibration is performed, then measurement precision is improved, but loss of time occurs due to requiring field of view clearance
Solution Approach 1:
The system performs calibration as a preliminary action that can be executed with objects already in place, eliminating the time-consuming step of removing objects before calibration. The calibration is performed in advance using the actual examination configuration, so no additional time is lost for field of view clearance.
4Measurement precision
If objects are removed for calibration, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The calibration system uses the objects already present in the field of view during normal operation. Rather than requiring external intervention to remove objects, the system self-calibrates using the existing configuration, making operation easier while maintaining measurement precision through data segmentation.
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
Enables accurate correction of measurements by computing gain corrections from calibration data, reducing errors caused by partial obstructions, and improving the reliability of CT system outputs even when objects are present in the field of view.
Implementation Method 1
measuring attenuation by the subject (e.g., which may be indicative of the density of the subject and/or aspects thereof). In some embodiments, an image(s) is formed based upon the radiation absorbed and/or attenuated by interior aspects of the subject, or rather an amount of photons that is able to pass through the subject
Implementation Method 2
the subject is exposed to radiation comprising photons (e.g., such as x-ray photons, gamma ray photons, etc.) to measure attenuation by the subject
Data Source
AI summary
Among other things, one or more techniques and/or systems for calibration of a radiation system to compute a gain correction(s) are provided. A calibration procedure is performed during which a portion of the detector array is shadowed by an object, causing the detector array to be non-uniformly exposed to radiation. A portion of a projection generated from the calibration procedure and indicative of radiation that did not traverse the object is separated from a portion of the projection indicative of radiation that did traverse the object, and a gain correction(s) is computed from the portion of the projection indicative of radiation that did not traverse the object (e.g., and is thus indicative of radiation that merely traversed air).