Sequential Clipping Circuit for Linear Time-Over-Threshold Imaging
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Solution Overview
Problem
Radiological imaging equipment using time-over-threshold (TOT) signal processing with a time-to-digital convertor (TDC) faces poor energy linearity, particularly with X-rays and gamma-rays having continuous energy spectra, limiting its application and accuracy.
Innovation Solution
A signal processing device incorporating a diode-based clipping circuit with two sequential clipping stages to enhance energy linearity, utilizing a first and second clipping circuit to process signals above a threshold, followed by a TDC for digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-channel radiation detector with optical sensors is used to improve imaging performance, then anatomical and physiological image information accuracy is improved, but signal processing burden increases
Solution Approach 1:
The patent extracts only the essential timing information from the full radiation signal by using a threshold comparator to generate a digital pulse when the signal exceeds a threshold. This extracts the time-over-threshold parameter while discarding unnecessary amplitude information, thereby reducing processing burden while maintaining imaging accuracy.
Solution Approach 2:
Instead of converting radiation signals to digital values through traditional ADC methods, the patent inverts the approach by converting the time duration that the signal exceeds a threshold into a digital value. This time-to-digital conversion simplifies the processing architecture while preserving the essential information needed for image reconstruction.
2Device complexity
If time-over-threshold signal processing with TDC is used to reduce system complexity, then data acquisition system complexity is reduced, but energy linearity deteriorates
Solution Approach 1:
The patent applies preliminary signal conditioning and amplification before the threshold comparison stage. By pre-processing the signal to ensure proper amplitude and shape characteristics before threshold detection, the system maintains better energy linearity in the subsequent time-over-threshold measurement while still using the simpler TDC architecture.
Solution Approach 2:
The patent optimizes the threshold level parameter and the signal amplification gain to improve the linearity relationship between input energy and measured time-over-threshold values. By carefully selecting and adjusting these parameters, the system achieves improved energy linearity while maintaining the simplicity of the TOT-TDC approach.
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
The solution improves energy linearity, enhancing the accuracy and resolution of radiological imaging, particularly for X-rays with low energy regions and continuous spectra, while maintaining complexity reduction benefits of TOT-TDC systems.
Implementation Method 1
a scintillation method detects radiation rays and converts the radiation rays into an optical signal
Implementation Method 2
a signal detector configured to convert a scintillation signal output from a scintillation crystal into an electrical signal
Data Source
AI summary
Radiological imaging equipment includes a signal detector configured to convert a scintillation signal output from a scintillation crystal into an electrical signal, and a signal processor configured to amplify an output signal of the signal detector and to output a time in which an amplified signal is maintained above a threshold, wherein the signal processor includes a first clipping circuit and a second clipping circuit configured to sequentially clip the amplified signal according to the threshold.