PET Scanner Calibration Using Centralized Radiation Source
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Solution Overview
Problem
Current PET scanner calibration methods using phantoms are complex and time-consuming due to the need for precise adjustment of detector units' time offsets, which affects the accuracy of time-of-flight (TOF) measurements for image reconstruction.
Innovation Solution
A method and system for calibrating PET scanners by determining the time offset between detector units based on calculated first and second TOFs, using a filter window and sinogram analysis to adjust the position of the radiation source and calibrate detector units, thereby improving the accuracy of TOF measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom is used to calibrate the PET scanner, then the accuracy of time offset calibration is improved, but the calibration process becomes more complex and time-consuming
Solution Approach 1:
The patent extracts the essential calibration function from the complex phantom-based method by using a simplified radiation source positioned at the center of the FOV. This removes the need for complex phantom structures while retaining the core calibration capability through direct measurement of time offsets from the centralized source.
Solution Approach 2:
The method performs preliminary positioning of the radiation source at the center of the FOV before calibration begins. This preliminary action establishes a known reference point that simplifies subsequent time offset measurements, eliminating the need for complex real-time adjustments during calibration.
2Measurement precision
If a device to adjust the position of the phantom is used, then the calibration accuracy is improved, but the calibration process becomes more complex
Solution Approach 1:
The patent removes the position adjustment device entirely by using a fixed centralized radiation source. The calibration accuracy is maintained not through mechanical adjustment but through the mathematical relationship between the known source position and detector response, extracting the essential measurement function without the complex positioning mechanism.
Solution Approach 2:
The patent replaces the mechanical position adjustment system with a computational approach. Instead of physically moving the source or phantom to achieve precise positioning, the system calculates time offsets based on the known geometric relationship between the centralized source and detectors, substituting mechanical complexity with mathematical processing.
3Reliability
If traditional phantom imaging method is used, then comprehensive calibration data is obtained, but the calibration time is increased
Solution Approach 1:
The patent segments the calibration process into essential measurements only, focusing on time offset calibration from the centralized radiation source. By dividing the calibration task into this focused component rather than attempting comprehensive phantom imaging, the system obtains sufficient calibration data in reduced time.
Solution Approach 2:
The method skips the time-consuming aspects of traditional phantom imaging by using the centralized source to directly measure time offsets. This allows the calibration process to rush through to the essential result without performing unnecessary intermediate steps required by conventional phantom-based methods.
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 simplifies the calibration process, enhances the accuracy of TOF measurements, and reduces the complexity of phantom imaging, leading to improved PET image reconstruction and scanner performance.
Implementation Method 1
coincidence events resulting from annihilation of positrons emitted by a radiation source
Implementation Method 2
Time-of-flight (TOF) information is generally used for PET image reconstruction. For an annihilation event, the time that each of the coincident photons is detected at two detector units
Data Source
AI summary
A method and system for calibrating a PET scanner are described. The PET scanner may have a field of view (FOV) and multiple detector rings. A detector ring may have multiple detector units. A line of response (LOR) connecting a first detector unit and a second detector unit of the PET scanner may be determined. The LOR may correlate to coincidence events resulting from annihilation of positrons emitted by a radiation source. A first time of flight (TOF) of the LOR may be calculated based on the coincidence events. The position of the radiation source may be determined. A second TOF of the LOR may be calculated based on the position of the radiation source. A time offset may be calculated based on the first TOF and the second TOF. The first detector unit and the second detector unit may be calibrated based on the time offset.