Multi-Pinhole Coded Aperture for PET Imaging
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Solution Overview
Problem
Current PET systems face challenges in accurately determining the location of annihilation events due to limited spatial coverage and high costs associated with time coupling technology, which requires expensive detectors and fast-responsive electronic circuits, leading to low effective coupling ratios and errors in imaging.
Innovation Solution
A multi-pinhole plate design is introduced, allowing for collimation of gamma photons and enabling the detection of individual photons without time coupling, which reduces system costs and improves detection accuracy by allowing non-ring detector arrangements and the use of less expensive detector components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If time coupling technology is used to detect gamma photons, then the efficiency in counting individual gamma photons is improved, but the system cost increases due to expensive detectors and fast-responsive electronic circuits
Solution Approach 1:
The patent extracts the time coupling function from the detector system and replaces it with a coded aperture mask. This separates the collimation function (performed by the mask) from the detection function (performed by simpler detectors), thereby eliminating the need for expensive fast-responsive electronic circuits while maintaining gamma photon counting efficiency
Solution Approach 2:
The coded aperture mask acts as an intermediary device between the gamma photons and the detectors. It performs the collimation and spatial encoding function that would otherwise require complex time coupling electronics, allowing simpler detectors to achieve the same imaging capability
2Reliability
If time coupling technology is used to detect gamma photons, then the imaging capability is improved, but the effective coupling ratio decreases due to limited spatial coverage
Solution Approach 1:
The patent transitions from a ring-shaped detector arrangement (two-dimensional coverage) to a coded aperture mask with multiple pinholes that creates a three-dimensional detection geometry. This dimensional change allows detectors to capture gamma photons from multiple angles simultaneously, improving spatial coverage and the effective coupling ratio while maintaining imaging capability
3Productivity
If multiple annihilation events occur within a short time window, then the counting rate increases, but the system cannot determine the event location causing errors
Solution Approach 1:
The patent replaces the electronic time coupling system with a geometric coded aperture mask. Instead of using fast electronics to resolve temporal coincidences, the mask uses its physical structure to spatially separate and identify photon paths, thereby maintaining location determination accuracy even when multiple annihilation events occur within short time windows
4Device complexity
If only one gamma photon is detected, then the detection simplicity is improved, but there is no way to determine its traveling path
Solution Approach 1:
The coded aperture mask serves as an intermediary that encodes the traveling path information of individual gamma photons in the spatial pattern of detected photons. Even when only one photon is detected, the mask's structure provides the geometric information needed to determine the photon's origin, thereby preventing loss of path information while maintaining detection simplicity
Data Source
AI summary
The technical solution as put forth by the present invention comprises a computer imaging system and detectors arranged around the detected object for collecting gamma photons from positron annihilation events. The key is a multi-pinhole plate placed between the detected object and the detectors, and the multi-pinhole plate can be a coded aperture mask coded by using a function h(x,y). The gamma photons generated from the annihilation events inside the detected object are absorbed by the detector after being collimated by the multi-pinhole plate. Accordingly, after the detectors have performed detection at multiple angles, the result is transmitted to the computer imaging system, and quasi three-dimensional images are generated after being processed by the disclosed algorithm. Furthermore, the quasi three-dimensional images generate secondary projection images and, after adjustment, generate sinograms, and finally three-dimensional tomographic images are reconstructed from multiple sinograms.