Hybrid Pixel-Waveform Readout for Gamma Ray Detectors
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Solution Overview
Problem
Small-pixel CZT and CdTe detectors for ultrahigh resolution gamma ray imaging face challenges such as charge collection efficiency degradation due to charge loss and charge sharing effects, and require complex readout circuitry for high spatial resolutions, limiting their accuracy and portability.
Innovation Solution
A hybrid pixel-waveform readout system that includes a pixel readout circuit for anode pixels and a waveform sampling circuit for cathodes to determine interaction location, energy, timing, and depth-of-interaction, using semiconductor materials like CdZnTe and CdTe, which simplifies the readout process and improves accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If small-pixel CZT and CdTe detectors are used for ultrahigh resolution gamma ray imaging, then spatial resolution is improved, but charge collection efficiency is degraded due to charge loss and charge sharing effects
Solution Approach 1:
The detector is divided into two independent readout systems: a pixel readout circuit for spatial positioning and a waveform sampling circuit for energy and timing measurement. This segmentation allows each system to optimize for its specific function, with the pixel circuit providing precise spatial resolution and the waveform circuit accurately measuring energy despite charge sharing effects
Solution Approach 2:
The patent transitions from a single-plane pixel readout to a dual-plane configuration with anode pixels and cathode waveforms. By reading out signals from both the anode side (for spatial information) and the cathode side (for energy and timing information), the system captures interaction information from multiple dimensions, enabling accurate energy measurement even when charge sharing occurs within small pixels
2Measurement precision
If small-pixel detectors are used for higher spatial resolutions, then imaging resolution is improved, but readout circuitry complexity increases
Solution Approach 1:
The readout system is segmented into two independent circuits: a simplified pixel readout circuit that only needs to identify which pixel fired (providing spatial information), and a waveform sampling circuit that handles the complex tasks of energy and timing measurement. This segmentation reduces the complexity burden on any single circuit while maintaining ultrahigh spatial resolution capability
Solution Approach 2:
The patent extracts the complex energy and timing measurement functions from the pixel readout circuit and places them in a separate waveform sampling circuit. The pixel readout circuit is simplified to only perform pixel identification and triggering, while the waveform circuit handles the computationally intensive energy calibration and timing extraction, thereby reducing overall system complexity
3Reliability
If scintillator detectors with PMTs are used for gamma ray detection, then detection capability is achieved, but device size and shielding requirements increase
Solution Approach 1:
The patent replaces the mechanical/optical PMT-based detection system with a solid-state semiconductor detector that directly converts gamma rays to electrical signals. This substitution eliminates the need for bulky PMT tubes and their associated optical coupling components, while also reducing shielding requirements due to the inherent compactness and efficiency of solid-state detection materials like CZT and CdTe
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 solution enhances the accuracy of energy, spatial, and timing information for gamma ray imaging, allowing for more precise localization of interactions and improved ultrahigh resolution imaging without the need for complex readout circuitry, making it suitable for portable and high-resolution applications.
Implementation Method 1
solid state detectors include a material that directly converts gamma rays to electrons
Implementation Method 2
one or more scintillator detectors that emit a flash of light in response to a gamma ray interaction with the detector
Data Source
AI summary
A gamma ray detector apparatus comprises a solid state detector that includes a plurality of anode pixels and at least one cathode. The solid state detector is configured for receiving gamma rays during an interaction and inducing a signal in an anode pixel and in a cathode. An anode pixel readout circuit is coupled to the plurality of anode pixels and is configured to read out and process the induced signal in the anode pixel and provide triggering and addressing information. A waveform sampling circuit is coupled to the at least one cathode and configured to read out and process the induced signal in the cathode and determine energy of the interaction, timing of the interaction, and depth of interaction.