Trigger Skew Correction in PET Detectors Using Temperature-Dependent Energy
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Solution Overview
Problem
Conventional PET imaging systems face challenges in accurately determining photon arrival times due to detector heterogeneities and temperature variations, leading to incorrect coincidence detection and image reconstruction, as they rely on costly hardware temperature sensors with latency and limited temperature detection accuracy.
Innovation Solution
A system that determines relationships between trigger time skew and event energy changes at different temperatures to correct trigger times, eliminating the need for hardware temperature sensors by using a lookup table and FPGA for real-time execution, thereby improving timing accuracy and reducing latency and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hardware temperature sensors are used to detect temperature and correct event signals, then temperature-based trigger skew can be corrected, but the system incurs high cost, significant latency, and fails to detect actual detector temperature due to mounting location limitations
Solution Approach 1:
The patent uses an intermediary approach by measuring the temperature of a reference component (the reference detector or its substrate) that is thermally coupled to the actual detector, rather than directly measuring the detector temperature. This reference temperature serves as a proxy to correct trigger skew without requiring direct temperature sensors on each detector, reducing complexity while maintaining correction accuracy
Solution Approach 2:
The patent creates a thermal model or lookup table that copies the relationship between temperature and trigger skew from calibration data. During operation, the system uses this pre-established model to determine trigger skew corrections based on measured reference temperatures, avoiding the need for complex real-time temperature compensation algorithms and hardware sensors on each detector
2Measurement precision
If individualized scaling factors are applied to each event signal to bring signals to a same target peak amplitude, then partial photon energy deposition effects are corrected, but trigger timing skew due to such effects is not determined
Solution Approach 1:
The patent implements a feedback mechanism where the measured trigger times and signal amplitudes are used to update the trigger skew correction values in the lookup table. The system continuously refines the relationship between signal amplitude, temperature, and trigger skew based on actual operating conditions, ensuring accurate timing correction while maintaining signal amplitude consistency
Solution Approach 2:
The patent changes the approach from merely scaling signal amplitudes to also adjusting trigger time parameters. By determining trigger skew as a function of both signal amplitude and temperature, the system recovers timing information that would otherwise be lost, using parameter transformations to map corrected trigger times across different operating conditions
3Productivity
If conventional coincidence time window detection is used without temperature and energy correction, then the system operates simply, but photons from single annihilation may be determined as arriving outside the coincidence window and two photons from different annihilations may be falsely identified as coincidences
Solution Approach 1:
The patent performs preliminary correction of trigger times using temperature and energy-dependent skew values before the coincidence detection process. By pre-adjusting all trigger times based on their respective temperature and amplitude conditions, the system ensures that subsequent coincidence window comparisons are performed on accurately aligned time stamps, improving both true coincidence detection and false coincidence rejection
Solution Approach 2:
The patent replaces the simple fixed-time-window coincidence detection mechanism with a corrected time-stamp comparison approach. Instead of relying on uncorrected trigger times and a fixed coincidence window, the system uses temperature and energy-compensated trigger times, allowing for more accurate physical coincidence determination that accounts for varying detector response conditions
Data Source
AI summary
Systems and methods include determination of a first relationship between change in photopeak energy and event time skew based on a first detection event signal acquired from a detector at a first temperature and a subsequent detection event signal acquired from the detector at a next temperature, acquisition of a subsequent detection event signal from the detector, determination of an event time associated with this detection event signal, determination of an event time skew based on an energy of this detection event signal and the first relationship, determination of a corrected event time based on the event time and the event time skew, and identification of a coincidence based on the corrected event time.