Photon-Counting CT Pixel Screening for Intermittent Defect Detection
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Solution Overview
Problem
Existing photon-counting computed tomography (CT) systems face challenges in detecting and correcting defective pixels, particularly those with intermittent behavior, which can lead to image artifacts and degraded image quality due to issues like noisy counting, abnormal energy response, and non-linear energy response.
Innovation Solution
An on-the-fly defective pixel screening method is implemented using a photon-counting CT apparatus with processing circuitry to generate and update defective pixel maps based on calibration and object scans, employing criteria such as energy spectrum analysis and threshold comparisons to identify and correct defective pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photon-counting detectors are used to achieve spectral CT and higher resolution, then imaging capability and resolution are improved, but the complexity of detecting and correcting defective pixels increases
Solution Approach 1:
The system performs preliminary defective pixel detection during a calibration scan before the actual patient scan. This preliminary action identifies defective pixels in advance, allowing the system to flag and correct them during image reconstruction without interfering with the main imaging process.
Solution Approach 2:
The patent introduces an intermediary defective pixel map that stores identification information about defective pixels. This map acts as a mediator between the raw detector data and the image reconstruction process, enabling systematic handling of defective pixels through interpolation or weighting operations.
2Reliability
If conventional defective pixel screening methods are applied to photon-counting detectors, then some defective pixels can be detected, but intermittent defective pixels cannot be identified and cause ring artifacts
Solution Approach 1:
The system dynamically updates the defective pixel map by comparing data from multiple scans. Instead of relying on a static calibration, the system adapts to changing detector conditions by identifying pixels that consistently show abnormal behavior across multiple acquisitions, thereby detecting intermittent defects.
Solution Approach 2:
The patent implements a feedback mechanism where the defective pixel map is continuously refined based on scan results. The system uses scan data to update the defective pixel identification, which then feeds back into the next scan's processing, creating a closed-loop system that progressively improves detection accuracy.
3Reliability
If multiple scan acquisitions are performed to detect intermittent defective pixels, then detection accuracy is improved, but scan time increases
Solution Approach 1:
The system performs preliminary defective pixel detection during a calibration scan before the actual patient scan. This preliminary action identifies defective pixels in advance, allowing the system to flag and correct them during image reconstruction without interfering with the main imaging process.
Solution Approach 2:
The defective pixel detection process operates continuously across multiple scans without interrupting the imaging workflow. The system accumulates data from successive scans to refine the defective pixel map, ensuring that useful imaging action continues while detection accuracy improves over time.
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
The method effectively detects and corrects defective pixels, reducing image artifacts and ensuring high-quality image reconstruction by discarding or interpolating values from defective pixels, resulting in ring-free images.
Implementation Method 1
a semiconductor-based detector using direct conversion is employed to resolve the energy of the individual incoming photons
Implementation Method 2
When a photon deposits energy on the sensor materials (such as, for example, CdTe/CZT/Si) of a detector, a charge cloud is formed and drifts toward the anode under the applied electric field
Data Source
AI summary
An apparatus and a method for detection of defective pixels for a photon-counting detector-based computed tomography (CT) system is disclosed. In particular, the apparatus and the method disclosed herein, detect detector pixels that have intermittent behavior using on-the-fly defective pixel screening based on various criteria during an object scan. The defective pixels are discarded using a defective pixel map before image reconstruction.