Timing-Pick-Off Using Prototype Waveform and Weighting Function
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Solution Overview
Problem
Current PET imaging systems face limitations in timing resolution due to the difficulty in accurately determining the arrival time of PMT output signals, particularly because of the limitations of discrete elements and the blurring effect caused by averaging processes in extracting timing information from undersampled waveforms.
Innovation Solution
A photosensor-based radiation detection system that uses a processing unit to determine the arrival time and amplitude of digital signals by fitting them to a prototype waveform with a varying weighting function, which is empirically determined and optimized to improve timing resolution, specifically focusing on the leading edge of the signal where critical timing information is contained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete elements and conventional ADC sample rate technology are used to determine arrival time of PMT output signals, then the system is simpler to implement, but timing resolution and measurement precision deteriorate due to limited samples on the leading edge
Solution Approach 1:
The patent applies preliminary action by pre-determining the prototype waveform through averaging multiple pulses, then using this pre-established reference to guide the timing extraction process. The prototype waveform is stored and used as a template for subsequent timing-pick-off operations, eliminating the need to reprocess multiple pulses for each timing measurement.
Solution Approach 2:
The patent introduces an intermediary approach by using a timing-pick-off circuit that samples the PMT output at a reduced rate and compares these samples against the pre-determined prototype waveform. This intermediary sampling and comparison mechanism enables accurate timing extraction without requiring high-speed ADCs, thus reducing system complexity while maintaining timing resolution.
2Quantity of substance
If averaging process is used to extract timing information from undersampled waveforms, then more samples can be processed, but blurring is introduced to the leading edge where critical timing information is contained
Solution Approach 1:
The patent extracts only the essential timing information from the waveform by sampling at specific points on the leading edge and comparing these samples to the prototype waveform. Instead of processing the entire waveform through averaging, the method extracts timing-pick-off values that directly represent arrival time, eliminating the blurring effect of comprehensive averaging while still utilizing multiple samples.
Solution Approach 2:
The patent applies local quality by focusing processing efforts specifically on the leading edge region of the waveform where timing information is critical. The timing-pick-off circuit samples only the relevant portion of the signal and compares it to the corresponding region of the prototype waveform, rather than uniformly processing the entire waveform. This localized approach preserves timing accuracy while still benefiting from multiple samples.
3Measurement precision
If high ADC sample rate is used to capture leading edge information, then timing resolution improves, but the system complexity and cost increase
Solution Approach 1:
The patent uses preliminary action by pre-determining the prototype waveform characteristics before actual timing measurements. This pre-established reference contains all necessary timing information, allowing subsequent measurements to be made at lower sampling rates without sacrificing accuracy. The prototype waveform serves as a template that guides the timing extraction process.
Solution Approach 2:
The patent introduces an intermediary timing-pick-off circuit that bridges the gap between low-rate sampling and high timing precision requirements. This circuit samples the PMT output at a reduced rate (e.g., 100-500 MHz) and uses the pre-determined prototype waveform to interpolate and determine precise arrival times, eliminating the need for expensive high-speed ADCs while maintaining timing resolution.
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 quality of timing estimates by reducing blurring and improving timing resolution, allowing for more accurate positioning in PET imaging, even with undersampled signals, thereby improving the overall spatial resolution of PET scanners.
Implementation Method 1
PET imaging relies on the conversion of gamma rays into light through fast and bright scintillation crystals, generating the scintillation events referred to above
Implementation Method 2
arrival time determination of PMT output signals is difficult to achieve with significant accuracy
Data Source
AI summary
A process and device for generating a prototype waveform and a weighting function. The process including obtaining waveforms generated by a detector having at least one photosensor, generating an initial estimate for the prototype waveform and the weighting function and parameterizing the prototype waveform and the weighting function and determining for each waveform an optimal amplitude and an optimal time offset of the prototype waveform. Included are steps of pairing waveforms based on the determined time offsets of the waveforms, calculating an arrival time difference for each pair of waveforms and determining a timing resolution value based on the calculated arrival time differences, determining whether the timing resolution value meets predetermined minimization criteria, and updating the set of parameters for the prototype waveform and the weighting function and repeating the determining, pairing, calculating, and determining, when the timing resolution value fails to meet the predetermined minimization criteria.