Adaptive Data Acquisition Circuit for Imaging Systems
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Solution Overview
Problem
Conventional imaging data acquisition circuits face challenges in maintaining energy resolution over a wide range of photon counting rates, as low resistance values lead to decreased energy resolution due to ballistic deficit and increased count rates result in pile-up errors, distorting pulse amplitudes and causing miscounting.
Innovation Solution
An adaptive data acquisition circuit dynamically modifies operating parameters such as resistor values, pulse shaping time, and discrimination thresholds based on pulse rate and integrated charge, using a digital logic circuit to control these parameters and prevent amplifier saturation through folding circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a low resistance resistor is used in the feedback circuit to prevent amplifier saturation at high count rates, then the count capability is improved, but the energy resolution deteriorates due to ballistic deficit
Solution Approach 1:
The patent applies dynamics by making the feedback resistance variable rather than fixed. The circuit dynamically adjusts the feedback resistance value based on the detected count rate: using low resistance values during high count rates to prevent saturation, and high resistance values during low count rates to maximize energy resolution. This temporal variation in resistance allows the system to optimize for different operating conditions.
Solution Approach 2:
The patent implements parameter changes by modifying the feedback resistance parameter according to the operating conditions. The resistance value is changed from a fixed parameter to a variable parameter that adapts to the count rate, thereby resolving the contradiction between count capability and energy resolution across different operating regimes.
2Productivity
If the switch is closed frequently to reset the capacitor and prevent saturation, then the count capability is improved, but the detection of incident X-rays deteriorates due to missed pulses during reset period
Solution Approach 1:
The patent applies dynamics by making the reset switch operation conditional rather than periodic. The switch is closed only when the feedback resistance indicates high count rates that would cause saturation, and remains open during low count rates to ensure continuous detection. This dynamic control of the reset operation eliminates fixed dead time while maintaining protection against saturation.
3Measurement precision
If a long pulse shaping time is used to improve energy resolution, then the measurement precision is improved, but the productivity deteriorates due to increased circuit dead time and pulse pile-up at high count rates
Solution Approach 1:
The patent applies dynamics by making the pulse shaping time variable rather than fixed. The circuit uses long shaping times during low count rates to maximize energy resolution, and automatically shortens the shaping time during high count rates to reduce dead time and prevent pulse pile-up. This dynamic adjustment allows the system to maintain both high resolution and high count rate capability.
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 allows for consistent energy resolution across varying count rates, reducing errors and maintaining accurate photon counting by dynamically adjusting circuit settings in response to changing conditions.
Implementation Method 1
detector 12 generating current charge pulses responsive to received energy 11, such as x-ray photons incident on the detector 12
Implementation Method 2
an integrating capacitor 16, resistor element 18, and low impedance switch 119 connected in feedback between an inverting terminal and an output terminal of the op amp 15
Data Source
AI summary
An adaptive data acquisition circuit (26) includes an amplifier (14) for amplifying electrical pulses generated by a detector (12) responsive to energy incident at the detector. The adaptive data acquisition circuit also includes a counting circuit (28) for counting amplified electrical pulses generated by the amplifier. In addition, the adaptive data acquisition circuit includes a digital logic circuit (30) for determining a pulse parameter indicative of a pulse rate and an amount of energy present in the amplified electrical pulses and for generating a control signal (34) responsive to the pulse parameter for controlling an operating parameter of the data acquisition circuit.