Timing Trigger Circuit for Gamma Event Detection Under Noise
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Solution Overview
Problem
Conventional nuclear medical imaging systems face challenges in accurately determining timing triggers for gamma events due to false triggers caused by dark events and noise, leading to detector dead time and reduced timing resolution.
Innovation Solution
A system and method that utilize a timing trigger circuit with a receiver, comparators, and a timing trigger generator to analyze pulse signatures from photomultiplier sensors, identifying true gamma events by setting a predetermined number of triggers within a time interval and comparing a delayed pulse signature to a timing trigger level, thereby reducing false triggers and dead time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the trigger level is set very low to trigger on the first few photons received from the scintillator emission, then timing resolution is improved, but false triggers occur due to random dark events of the SiPM microcells and other noise sources
Solution Approach 1:
The patent applies preliminary action by implementing a verification scheme that checks the pulse height of triggers before accepting them for data acquisition. The system pre-establishes a minimum pulse height threshold and verifies each trigger against this threshold before proceeding, thereby preventing false triggers from dark events while maintaining low trigger levels for good timing resolution
Solution Approach 2:
The patent uses feedback by implementing a verification scheme where the output of the trigger is fed back through a pulse height analysis stage. The system continuously monitors pulse heights and uses this feedback information to accept or reject triggers, creating a closed-loop system that maintains reliability while preserving timing precision
2Reliability
If verification schemes are implemented to filter false triggers, then false trigger rate is reduced, but detector dead time increases due to the time required for verification and data acquisition preparation
Solution Approach 1:
The patent applies partial action by implementing a streamlined verification scheme that checks only the essential pulse height parameter rather than performing exhaustive analysis. The system performs just enough verification to filter false triggers effectively while minimizing the time spent in verification mode, thereby reducing dead time while maintaining reliability
3Reliability
If conventional detectors wait at least twenty nanoseconds to verify triggers and prepare for the next event, then false triggers are filtered, but the detector is not ready for the next gamma event, reducing productivity
Solution Approach 1:
The patent applies preliminary action by pre-establishing verification thresholds and having the verification circuitry ready in advance. The system prepares the verification mechanism beforehand so that when a trigger occurs, the verification can proceed immediately without lengthy preparation delays, reducing the twenty-nanosecond wait time while maintaining effective false trigger filtering
Solution Approach 2:
The patent implements continuity of useful action by designing a verification scheme that operates continuously and efficiently. The verification circuitry remains active and ready, processing triggers as they arrive without significant idle time. This continuous operation maintains reliability while maximizing the detector's productivity by minimizing gaps between event detections
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 of timing resolution for gamma events while minimizing the impact of dark events and noise, reducing detector dead time and improving the efficiency of data acquisition for nuclear imaging.
Implementation Method 1
A conventional block detector for identifying gamma events utilizes an array of photomultiplier tubes (PMTs). The array of PMTs identifies a gamma-ray scintillation event
Implementation Method 2
The array of PMTs identifies a gamma-ray scintillation event (for example, a gamma event) within a pixelated scintillation crystal block
Implementation Method 3
Recently, silicon photomultipliers (SiPMs) have been implemented as photosensors for reading out the scintillation light of LSO (Lutetium Oxyorthosilicate) and other PET scintillators
Data Source
AI summary
Systems and methods of generating timing triggers to determine timing resolutions of gamma events for nuclear imaging includes receiving a pulse signature representing a succession of triggers associated with a photomultiplier. When a number of triggers occurring within a predetermined time interval matches a predetermined number, an event trigger can be initiated. A delayed version of the pulse signature can be generated and compared to a predetermined timing trigger level. When the delayed version matches the predetermined timing trigger level, a timing trigger can be generated. Based on the timing trigger level, the timing trigger can be generated at the pulse of the delayed version that corresponds to the first photoelectron of a gamma event. The timing trigger can correspond to a timestamp for the first photoelectron so that a data acquisition system can identify the pulse from which to acquire energy information to generate a nuclear image.