PET Scintillator Time Calibration Using LOR Statistics
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Solution Overview
Problem
Current PET systems face challenges in achieving universal and efficient time calibration for scintillator bars due to varying methods required for different target objects, leading to time-consuming processes and inaccurate results, especially when dealing with non-uniformly shaped targets.
Innovation Solution
A method involving determining lines of response (LOR) passing through a target object, calculating pixel value-time difference and coincidence event-time difference statistical distributions, and using an inner product to determine time offset differences for each LOR, allowing for standardized time calibration without Gaussian fitting or high drug activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional time calibration methods using Gaussian fitting are employed, then measurement precision can be achieved, but calibration time becomes excessively long (at least 1 hour)
Solution Approach 1:
The patent replaces the traditional Gaussian fitting mathematical method with a statistical distribution method based on coincidence events. Instead of using complex curve fitting algorithms that require extensive data collection and computation, the invention uses direct statistical analysis of time difference distributions from coincidence events, significantly reducing calibration time while maintaining precision.
Solution Approach 2:
The patent changes the approach from fitting entire Gaussian curves to analyzing specific statistical parameters (mean and standard deviation) of time difference distributions. By focusing on key statistical characteristics rather than complete curve fitting, the method achieves comparable precision with much faster computation and shorter calibration time.
2Measurement precision
If high drug activity is used to improve signal strength for calibration, then measurement precision improves, but safety risks and measurement errors from random events increase
Solution Approach 1:
The patent extracts and utilizes only the relevant statistical information (time difference distributions) from coincidence events, discarding unnecessary data. By focusing specifically on the statistical characteristics of coincident gamma photon pairs, the method achieves accurate calibration without requiring high drug activity that would generate excessive random events and safety concerns.
Solution Approach 2:
The calibration method uses the natural coincidence events that occur during normal PET operation to perform self-calibration. The system leverages its own operational data rather than requiring separate high-activity calibration procedures, enabling accurate time offset determination while maintaining safety by using常规 drug activities.
3Adaptability or versatility
If different calibration methods are used for different target objects, then adaptability is reduced, but the process becomes more complex and time-consuming
Solution Approach 1:
The patent develops a universal calibration method that works for all target objects regardless of shape or activity distribution. By using statistical analysis of coincidence events from any target configuration, the single method can determine time offsets for all scintillator bars universally, eliminating the need for multiple specialized procedures and reducing overall 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 enables efficient and accurate time calibration applicable to any target shape, reducing calibration time and eliminating the need for high drug activity, thereby improving PET system precision.
Implementation Method 1
the detection principle of PET system is that positron nuclide decay produces a positron, the positron annihilates with surrounding electrons, producing a pair of gamma photons with opposite directions and energy of 511 keV each, and if two gamma photons are respectively detected by two scintillation crystal bars of the PET detector
Data Source
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AI summary
In the disclosure disclosed are a time calibration method, device, apparatus, and computer-readable storage medium. The time calibration method comprises determining lines of response passing through a target object and coincidence events on each line of response based on sampling data of the target object, acquiring an activity image, and determining pixel points where the respective lines of response passing through the target object intersect with the activity image, and determining a pixel value-time difference statistical distribution corresponding to each line of response based on the pixel points respectively; determining a coincidence event-time difference statistical distribution corresponding to each line of response based on the coincidence events on each line of response; calculating a maximum value of inner product of the pixel value-time difference statistical distribution and the coincidence event-time difference statistical distribution and determining a time offset difference value corresponding to the maximum value Yi for each line of response; and determining a time calibration value based on the offset difference value. The disclosure is widely applicable, does not require prolonged sampling, thereby saving time and enhancing the efficiency of time calibration.