Pixelated Gamma Detector Depth Measurement via Photon Timing
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Solution Overview
Problem
Conventional PET detectors face challenges in determining the depth of interaction (DOI) due to geometric parallax and uncertainty in photon flight time, leading to complex processing and degradation of energy measurement, especially with Compton scattering, which is exacerbated by the use of expensive LSO scintillators and requires multiple electronic channels.
Innovation Solution
A method that measures the arrival time of first photons on a central pixel and an adjacent pixel, using a precision ASIC component to estimate interaction depth and integrate energy emission, reducing ambiguity through differential light propagation speeds and semi-transparent diffusing media, allowing for precise measurement of unscattered photons and energy determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual detector layers are used to determine depth of interaction, then measurement precision is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical/optical dual-layer detector system with an electronic time-measurement system. By measuring the arrival time of photons with high-precision timing electronics (sub-100ps resolution), the system determines depth of interaction without requiring complex dual-detector geometries, thus reducing device complexity while maintaining measurement precision
Solution Approach 2:
The invention changes the measurement parameter from spatial arrangement (dual layers) to temporal measurement (photon arrival time). This parameter transformation allows depth determination through time differences caused by light propagation speed variations, eliminating the need for complex mechanical detector structures
2Measurement precision
If dual detector layers are used to determine depth of interaction, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive dual-layer detector manufacturing with a single-layer detector combined with precision timing electronics. This substitution dramatically simplifies the manufacturing process, reduces material requirements, and lowers production costs while achieving the same depth measurement capability through temporal rather than spatial differentiation
3Speed
If LSO scintillators are used to improve detection speed, then measurement precision is improved, but cost increases
Solution Approach 1:
The invention changes the approach to achieving fast detection from material selection (expensive LSO) to timing measurement capability (electronic precision). By using high-resolution timing electronics, the system can achieve sub-100ps resolution with cheaper scintillator materials, thereby reducing material costs while maintaining fast detection speed through parameter transformation
4Measurement precision
If multiple electronic channels are used to read dual detector layers, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces the need for multiple electronic channels reading dual detector layers with a single electronic channel that performs time-correlated single photon counting. This substitution reduces the electronic channel count from multiple to one, significantly simplifying the electronic architecture while maintaining depth measurement precision through temporal resolution
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 spatial resolution, reduces ambiguity in Compton events, and decreases system costs by eliminating the need for dual detector layers, making it suitable for industrial implementation with Lanthanum halide scintillators, which are cheaper and faster than LSO.
Implementation Method 1
The invention relates to a method for determining the depth of an interaction in a pixelated detector of gamma radiation by scintillation
Implementation Method 2
coupled to a silicon photodiode on one side and, on the opposite side, coupled to a photomultiplier tube
Implementation Method 3
measuring the arrival time (Tpc) of said first photons on the detector for a central pixel; this time is equal to Ti + Z / (c/n)
Implementation Method 4
c/2n corresponds to the speed of propagation of the radiation in said pixel adjacent to the central pixel
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention concerns a method for determining the depth of an interaction in a pixellated gamma radiation detector characterised in that it comprises the following steps: - detecting first photons on the detector (10); - measuring the arrival time (Tpc) of said first photons on the detector (10) for a central pixel; - measuring the arrival time (Tpa) of the first photons in a pixel adjacent to said central pixel; - comparing the time (Tpa) with the time (Tpc) in order to estimate the interaction depth (Z) owing to the different light propagation speeds in adjacent pixels; - integrating the radiation emitted over the whole of the emission of a crystal of the detector in order to determine the energy of the interaction; and - recording the integral of the energy emitted by this detection. The invention further concerns a pixellated gamma radiation detector for implementing the above method. The invention further concerns a method of time calibration of pixellated detectors between same and the application of said pixellated detector in PET imaging.