Photon Counting Detector Hybrid Pixel Pattern Design
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Solution Overview
Problem
Photon-counting CT detectors face challenges in high-flux and low-flux scanning environments due to pulse pileup and charge sharing issues, with smaller pixels alleviating pileup but increasing charge sharing, and larger pixels reducing charge sharing but exacerbating pileup, making it difficult to maintain effective detector response across varying flux conditions.
Innovation Solution
A hybrid pixel pattern design is implemented, where macro-pixels consist of a combination of small and large micro-pixels, allowing the detector to be relatively immune to pulse pileup and charge sharing in both high-flux and low-flux environments by dynamically switching between micro-pixel sizes based on scanning conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If smaller pixel size is used for photon counting detector, then pulse pileup is reduced and detector is more immune to saturation, but charge sharing and signal cross talk between neighboring pixels increase
Solution Approach 1:
Each macro-pixel is divided into multiple micro-pixels of different sizes (small, medium, and large micro-pixels). This segmentation allows the detector to handle high-flux conditions by using smaller micro-pixels that are less prone to pulse pileup, while larger micro-pixels can be used when charge sharing is less problematic, thus resolving the contradiction between pulse pileup resistance and charge sharing effects.
Solution Approach 2:
Different regions within each macro-pixel have different micro-pixel sizes tailored to local requirements. Small micro-pixels are positioned where high count rates are expected to minimize pulse pileup, while larger micro-pixels are placed where charge sharing is less of an issue. This local optimization resolves the contradiction by adapting pixel size to local flux conditions.
2Measurement precision
If larger pixel size is used for photon counting detector, then charge sharing and cross talk effects are reduced, but pulse pileup becomes more severe in high-flux environments
Solution Approach 1:
The macro-pixel is segmented into multiple micro-pixels with different sizes. This allows the system to use larger micro-pixels when charge sharing is the primary concern, while smaller micro-pixels within the same macro-pixel can handle high-flux conditions, thus resolving the contradiction between charge sharing reduction and pulse pileup prevention.
Solution Approach 2:
The system dynamically selects which micro-pixel to use based on the actual flux conditions. When flux is high, smaller micro-pixels are activated to avoid pulse pileup; when flux is low, larger micro-pixels can be used to minimize charge sharing. This dynamic adaptation resolves the contradiction by adjusting effective pixel size based on operating conditions.
3Productivity
If uniform small pixel design is used, then high-flux performance is improved, but performance in low-flux scenarios deteriorates due to increased charge sharing
Solution Approach 1:
Each macro-pixel contains multiple micro-pixels of different sizes, making the detector universally applicable to both high-flux and low-flux scanning scenarios. The system can select the appropriate micro-pixel size based on the scanning conditions, thus achieving both high-flux performance and low-flux material decomposition accuracy within the same detector design.
4Measurement precision
If uniform large pixel design is used, then low-flux performance is improved, but high-flux performance deteriorates due to severe pulse pileup
Solution Approach 1:
The macro-pixel design with multiple micro-pixel sizes provides universal functionality across different flux conditions. Larger micro-pixels improve low-flux material decomposition accuracy, while smaller micro-pixels within the same macro-pixel handle high-flux scenarios, making the detector universally effective for both applications.
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 hybrid pixel pattern design enables the photon-counting detector to maintain adequate detector response and minimize pulse pileup and charge sharing across dynamic flux changes, improving material decomposition and reducing noise in both high-flux and low-flux scanning environments.
Implementation Method 1
A photon-counting detector (PCD) includes a semiconductor crystal
Data Source
AI summary
According to one embodiment, a photon-counting detector (PCD) includes a plurality of macro-pixels. The plurality of macro-pixels arranged on a semiconductor crystal has a first face and a second face. The first face and the second face are parallel. Each macro-pixel from the plurality of macro-pixels is configured to acquire projection data for generating a reconstructed image. The plurality of macro-pixels each includes at least one large micro-pixel is disposed within the each macro-pixel and at least two small micro-pixels is disposed within the each macro-pixel. Each of the at least two small micro-pixels has a surface area that is less than a surface area of the at least one large micro-pixel.