Scintillation Pulse Digitization Using FPGA Threshold Sampling
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Solution Overview
Problem
Conventional PET systems face challenges in achieving real-time correction and high accuracy in scintillation pulse sampling and processing due to their hybrid analog-digital circuit design, leading to increased power consumption and system cost.
Innovation Solution
An all-digital PET system is implemented using a scintillation pulse conversion unit, threshold comparison unit, time digitalizing unit, and data processing and transmission unit, which eliminates the need for comparators by utilizing a digital differential interface in a field programmable gate array to acquire and process scintillation pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold comparators are increased to improve sampling accuracy, then measurement precision is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent replaces the traditional analog threshold comparator circuit with a fully digital implementation using a field programmable gate array (FPGA). The scintillation pulse signal is sampled by an analog-to-digital converter (ADC) and then processed digitally to determine when the pulse exceeds threshold levels. This substitution of digital logic for analog comparison circuitry reduces power consumption while maintaining or improving measurement precision through the flexibility and accuracy of digital signal processing.
Solution Approach 2:
The patent changes the operating parameters of the system by implementing multiple threshold levels (e.g., 50%, 75%, 90% of maximum amplitude) that are programmably configured in the FPGA. This allows the system to achieve high measurement precision by capturing multiple crossing points of the scintillation pulse against different thresholds, thereby improving accuracy without requiring a proportional increase in hardware comparators, thus controlling power consumption.
2Measurement precision
If threshold comparators are increased to improve sampling accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated digital processing unit within the FPGA. The ADC, threshold comparison logic, timing measurement, and data output functions are combined in one digital system rather than using separate analog comparator circuits for each threshold level. This consolidation reduces device complexity and improves integration level while achieving high measurement precision through coordinated digital operations.
Solution Approach 2:
The FPGA-based digital processing unit serves multiple functions: it performs the threshold comparison, measures the timing of pulse crossings, handles multiple threshold levels simultaneously, and manages data output. This multi-functional approach replaces what would traditionally require multiple dedicated comparator circuits, thereby reducing overall device complexity while maintaining high measurement accuracy through its universal processing capability.
3Ease of manufacture
If hybrid analog-digital circuit is used, then ease of manufacture is improved, but reliability deteriorates due to difficulty in real-time correction
Solution Approach 1:
The patent replaces the hybrid analog-digital architecture with a fully digital system. The analog front-end that traditionally required careful calibration and had limited correction capability is replaced with digital sampling and processing. This substitution enables full digital control and correction, improving reliability by allowing real-time adjustment of sampling parameters, threshold levels, and timing measurements through software or programmable logic, while maintaining manufacturing feasibility through standardized digital components like ADC and FPGA.
Data Source
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AI summary
A method for digitalizing a scintillation pulse, comprising: setting n threshold voltages V_th according to the features of a scintillation pulse; forming a voltage comparison unit by n low voltage differential signal reception ports, and when a pulse to be sampled goes over any one threshold, the voltage comparison unit outputting a state jump and a threshold voltage corresponding to the state jump; and performing digital sampling at the time of the state jump using a time-to-digital converter; and at the same time, identifying the threshold voltage corresponding to the state jump, and acquiring a scintillation pulse voltage-time pair to complete the digitalization of the scintillation pulse. A device for digitalizing a scintillation pulse, comprising a scintillation pulse conversion unit, a threshold comparison unit, a time digitalization unit and a data processing and transmitting unit. The present invention realizes threshold comparison using a digital differential interface in a field programmable gate array and acquires a voltage-time pair of a scintillation pulse, so as to realize digitalization of the scintillation pulse, greatly simplify the system structure, improve the integration level of the system, and reduce the power consumption of the system.