Spectral CT Material Decomposition Path-Length Correction

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Solution Overview

Problem

Spectral computed tomography (CT) imaging systems face challenges in maintaining high spectral fidelity due to variations in detector efficiency, leading to reduced image quality and accuracy in material density estimation, especially with low signal-to-noise ratio (SNR) caused by underperforming detector elements.

Innovation Solution

The method involves identifying regions of low-performing detector pixels, enhancing their signal, and applying correction functions to improve spectral fidelity by generating corrected path-length measurements, which are then used for reconstructing material density images, incorporating dynamic or predetermined correction functions based on detector performance issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If spectral CT imaging is performed with standard detector arrays, then imaging capability is achieved, but spectral fidelity deteriorates due to detector efficiency variations

Engineering Contradiction:

Improvespectral fidelityVSAvoiddetector efficiency consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system performs preliminary calibration scans using phantoms with known material compositions before actual imaging. This preliminary action characterizes each detector element's spectral response and efficiency, storing this information for later correction during material decomposition, thereby compensating for detector variations and improving spectral fidelity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where measured projection data is compared against expected spectral responses from calibration data. Correction functions are dynamically adjusted based on this feedback to account for detector performance variations, ensuring accurate material density estimation despite detector inefficiencies

Inventive Principle:

Principle #23Feedback

2Measurement precision

If correction functions are applied to improve spectral fidelity, then measurement precision improves, but computational complexity increases

Engineering Contradiction:

Improvematerial density estimation accuracyVSAvoidcomputational processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Correction functions are pre-computed and stored during calibration phases based on phantom scans. These pre-computed correction lookup tables are then applied during actual imaging without requiring complex real-time calculations, reducing computational burden while maintaining accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system transforms the complex material decomposition problem into a parameter correction problem. Instead of solving full spectral decomposition with all detector variations, it applies targeted parameter corrections to path-length measurements based on calibration-derived correction functions, simplifying the computational task while preserving accuracy

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If photon-counting detectors are used to enhance spectral information, then imaging capability is improved, but sensitivity to detector element variations increases

Engineering Contradiction:

Improvespectral information retentionVSAvoidspectral fidelity

Core Design Contradiction:

Loss of informationVSMeasurement precision

Solution Approach 1:

The system applies individualized correction functions to each detector element based on its specific calibration characteristics. Instead of treating all detectors uniformly, it accounts for local variations in quantum efficiency and spectral response of each detector element, thereby maintaining spectral fidelity across the entire detector array

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Comprehensive calibration scans are performed preliminarily to characterize each photon-counting detector element's spectral response across multiple energy bins. This preliminary characterization enables the system to compensate for the high sensitivity of photon-counting detectors to efficiency variations, preserving spectral information accuracy

Inventive Principle:

Principle #10Preliminary action

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 enhances the spatial and contrast resolution, reduces image artifacts, and improves the accuracy of material density estimation, leading to improved spectral fidelity and image quality in CT imaging systems.

Implementation Method 1

detector array comprising a plurality of detector elements... to acquire projection data of the subject

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11337671B2Methods and systems for improved spectral fidelity for material decomposition

Publication Date: 2022.05.24 GE PRECISION HEALTHCARE LLC

AI summary

Various methods and systems are provided for spectral computed tomography (CT) imaging. In one embodiment, a method comprises performing a scan of a subject to acquire, with a detector array comprising a plurality of detector elements, projection data of the subject, generating corrected path-length estimates based on the projection data and one or more selected correction functions, and reconstructing at least one material density image based on the corrected path-length estimates. In this way, the fidelity of spectral information is improved, thereby increasing image quality for spectral computed tomography (CT) imaging systems, especially those configured with photon-counting detectors.