PET Scanner Calibration via Time Offset Calculation
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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 and radiation source positioning, which complicates the determination of accurate time offsets for accurate TOF-based 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 times of flight (TOFs) of coincidence events, using a filter window and sinogram analysis to adjust the position of the radiation source and calibrate detector units, thereby simplifying the calibration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom is used to calibrate the PET scanner with precise detector unit adjustment and radiation source positioning, then the measurement precision of time offset is improved, but the device complexity and operation complexity increase
Solution Approach 1:
The patent extracts the essential calibration function from the complex phantom-based system by using a simplified radiation source positioned at the center of the field of view. This removes the need for complex phantom structures and positioning mechanisms while retaining the core calibration capability through direct TOF measurement of coincidence events.
Solution Approach 2:
The calibration process utilizes the PET scanner's own detection capabilities and coincidence event data to automatically determine time offsets. The system self-calibrates by processing its detected coincidence events without requiring external phantom objects or complex positioning devices, making the calibration process simpler and more integrated.
2Measurement precision
If traditional phantom-based calibration methods are used with precise positioning requirements, then the measurement precision is improved, but the loss of time increases
Solution Approach 1:
The system performs calibration using its own operational data (coincidence events from normal scanning) rather than requiring separate phantom-based calibration procedures. This integrates calibration into the regular operation, eliminating the need for dedicated calibration time and allowing continuous operation without interruption.
Solution Approach 2:
The calibration data is collected and processed during normal scanning operations before formal image reconstruction begins. By preparing calibration information in advance during routine operations, the system avoids time-consuming separate calibration sessions while maintaining accurate time offset values.
3Measurement precision
If complex phantom adjustment procedures are used, then the measurement precision of detector calibration is improved, but the ease of operation deteriorates
Solution Approach 1:
The patent removes the phantom from the calibration process entirely, replacing it with a simple centralized radiation source. This extraction eliminates the need for complex phantom positioning and adjustment operations, making the calibration process much simpler to execute while maintaining calibration accuracy through direct TOF measurement.
Solution Approach 2:
The system automatically processes coincidence events to determine time offsets without requiring manual phantom positioning or adjustment. The automated processing of detection data simplifies operator tasks to merely initiating the calibration routine, dramatically improving ease of operation while preserving measurement precision.
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 the accuracy and efficiency of PET scanner calibration, reducing the complexity and time required for phantom imaging and detector unit calibration, leading to improved TOF-based image reconstruction and scanner performance.
Implementation Method 1
detecting coincidence events resulting from annihilation of positrons emitted by a radiation source
Implementation Method 2
calculate a first time of flight (TOF) of the LOR based on the plurality of coincidence events
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.