Computed Tomography Scanner Self-Calibration via Projection Data Analysis

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Solution Overview

Problem

Computed tomography systems face challenges in accurately interpreting data due to non-uniform detector arrays and calibration issues, which can lead to unreliable scanning results and inefficient calibration processes.

Innovation Solution

The method involves determining scanning geometry parameters using object projection data to adjust for physical anomalies, allowing for on-the-fly calibration and data correction without the need for a separate calibration step, using relative movement between the energy source/detector array and the object to identify parameters such as the axis of rotation and sample pitch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional calibration objects are used, then calibration accuracy can be achieved, but calibration time and system downtime increase

Engineering Contradiction:

Improvecalibration accuracyVSAvoidcalibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs self-calibration by automatically determining geometric parameters (detector element spacing, rotation axis position, fan angle) through analysis of projection data from the object being scanned. This eliminates the need for separate calibration objects and dedicated calibration time, allowing the system to calibrate itself during normal operation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The calibration parameters are determined before the actual scanning of the object of interest. By pre-determining the geometric parameters from projection data, the system prepares the necessary calibration information in advance, which then can be used for accurate reconstruction without requiring additional calibration time during the scanning process.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If calibration objects are used, then scanning geometry can be calibrated, but the form factor and weight differences affect calibration reliability

Engineering Contradiction:

Improvescanning geometry calibrationVSAvoidcalibration reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Instead of using a physical calibration object with specific form factors and weights, the system creates a virtual calibration model by extracting geometric parameters from projection data. This digital copy of the calibration information eliminates the physical limitations and measurement errors associated with actual calibration objects, improving reliability.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical calibration process (using physical calibration objects with known dimensions) with a computational approach. Geometric parameters are determined through mathematical analysis of projection data, substituting physical measurement and mechanical calibration procedures with digital signal processing and parameter estimation algorithms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If separate calibration step is performed, then scanning accuracy can be ensured, but productivity decreases due to downtime

Engineering Contradiction:

Improvescanning accuracyVSAvoidsystem productivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent merges the calibration process with the normal scanning operation. The same projection data collected during routine scanning of the object of interest is used to determine calibration parameters, combining what were previously separate steps (calibration then scanning) into a single integrated process, thereby maintaining productivity while ensuring accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system maintains continuous useful action by performing calibration during the scanning process rather than stopping for separate calibration. The projection data is continuously processed to determine geometric parameters, ensuring that the system remains operational and productive throughout the entire scanning sequence without interruption.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS9052265B2Method and apparatus to facilitate determination of a parameter that corresponds to a scanning geometry characteristic

Publication Date: 2015.06.09 VAREX IMAGING CORP

AI summary

Relative movement about an axis of rotation is caused as between an energy source/detector array with respect to an object (where the object can comprise either an object to be projected to facilitate a study of the object or a calibration object to be projected as part of calibrating usage of the energy source/detector array). The energy source/detector array are used during this relative movement to scan the object and to obtain corresponding object project data. That object projection data is then used to determine a parameter as corresponds to at least one scanning geometry characteristic as corresponds to using the energy source and the corresponding detector array while causing the aforementioned relative movement to scan the object.