Adaptive Timing Window for PET Image Reconstruction
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Solution Overview
Problem
Current PET systems produce relatively low-quality images compared to MR and CT images due to limitations in detecting gamma ray photons, particularly in tailoring the timing window for accurate detection event pairs.
Innovation Solution
A PET system with a reconstruction apparatus that includes a position providing unit, timing window determination unit, and detection event pairs generation unit to tailor the timing window based on the position and orientation of the inner detector relative to the outer detector, generating improved detection event pairs for enhanced image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed time coincidence window is used for detecting gamma ray photons, then the detection process is simple, but the PET image quality is low due to inclusion of random coincident events
Solution Approach 1:
The patent applies dynamics by making the time coincidence window adaptive rather than fixed. The window width is dynamically adjusted based on the distance between detector pairs, with closer detectors using narrower windows and farther detectors using wider windows. This dynamic adaptation resolves the contradiction by improving image quality through reduced random coincidents while maintaining detection efficiency across different spatial configurations.
Solution Approach 2:
The patent changes the parameter of time coincidence window width based on spatial parameters (detector distance). By varying the temporal parameter (window width) according to the spatial parameter (detector separation distance), the system optimizes the balance between accepting true coincident events and rejecting random coincidents, thereby improving PET image quality without excessive complexity.
2Measurement precision
If a narrow time coincidence window is used, then random coincident events are reduced, but true coincident events may be missed
Solution Approach 1:
The system dynamically adjusts the time coincidence window width based on detector pair distance. For close detector pairs, a narrow window reduces random coincidents while still capturing true coincidents due to their short flight path. For distant detector pairs, a wider window compensates for the longer photon flight time, ensuring true coincidents are not missed. This dynamic approach resolves the contradiction between detection accuracy and efficiency.
Solution Approach 2:
The patent applies local quality by tailoring the time coincidence window parameter to each specific detector pair's spatial characteristics. Instead of using a uniform window width, each detector pair receives a customized window width appropriate to its distance from the radiation source, optimizing the local detection conditions for both accuracy and efficiency.
3Measurement precision
If position-based timing window tailoring is implemented, then detection event pair accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent changes the timing window parameter based on position parameters (detector coordinates and distances). The reconstruction apparatus calculates the optimal window width for each detector pair using their spatial positions, improving detection event pair accuracy. While this increases computational requirements, the principle of parameter changes provides a systematic approach that balances accuracy improvement with manageable computational complexity.
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 leads to improved PET image quality by accurately tailoring the timing window, reducing random coincident detection events, and enhancing the accuracy of detection event pairs, resulting in higher image fidelity.
Implementation Method 1
radioisotopes decay by positron emission. When a positron is emitted by a nucleus, it almost instantly finds an electron, and the pair annihilates, converting all the mass energy of the two particles into gamma ray photons
Implementation Method 2
a first detector with first detector elements for detecting photons emitted by a radiation source located within the object and for generating first detection events
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A reconstruction apparatus (9) reconstructs a PET image. A first detector (3) generates first detection events and detection times assigned to the first detection events and a second detector (6) generates second detection events and detection times assigned to the second detection events. A timing window determination unit (11) provides a first-second timing window by providing a first-second upper threshold based on the position of the second detector relative to the first detector and a detection event pairs generation unit (12) generates first-second detection event pairs based on the provided first-second timing window. The first-second detection event pairs are used for reconstructing the PET image. The first-second timing window depends on the position of the second detector leads to an improved generation of first-second detection event pairs, which in turn can lead to an improved PET image.