CT Detector Tile Current-to-Frequency Signal Quantization
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Solution Overview
Problem
In computed tomography (CT) scanners, as detection technology advances to more slices, smaller slice widths, lower signals, and faster rotation times, noise and spatial resolution constraints limit imaging performance.
Innovation Solution
A detector tile with a scintillator array, photosensor array, and current-to-frequency converter is used, incorporating an integrator, comparator, sample and hold circuitry, and A/D converter to optimize signal processing by selectively activating the A/D converter based on the number of pulses generated during an integration period, reducing power consumption and improving signal quantization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the A/D converter is continuously activated during integration periods, then signal quantization is maintained, but power consumption increases
Solution Approach 1:
The A/D converter transitions between active and idle states dynamically based on pulse detection. When the comparator detects fewer than a threshold number of pulses during an integration period, the A/D converter remains active to sample the integrator output. When pulse counts exceed the threshold, the A/D converter enters idle state, adapting its operation to actual signal conditions and reducing unnecessary power consumption.
Solution Approach 2:
The system uses feedback from the comparator's pulse detection to control the A/D converter's operational state. The logic circuit monitors the number of pulses generated during integration and uses this information to determine whether the A/D converter should be activated, creating a closed-loop control system that optimizes power usage based on actual radiation signal levels.
2Measurement precision
If the detector array uses more slices and smaller slice widths, then imaging resolution is improved, but noise increases
Solution Approach 1:
The integrator continuously accumulates charge from the photosensor array over the integration period, maintaining continuous useful action in signal collection. This integration process sums multiple weak signals over time, improving the signal-to-noise ratio for small slice widths while preserving spatial resolution through the optically coupled scintillator and photosensor arrays.
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 imaging performance by reducing noise and improving spatial resolution, allowing for more efficient data acquisition and processing in CT scanners.
Implementation Method 1
The scintillator array generates light indicative of radiation impinging thereon
Implementation Method 2
the photosensor array generates an electrical signal indicative of the light
Data Source
AI summary
A detector tile (116) of an imaging detector array (112) includes a scintillator array (202), a photosensor array (204), which includes a plurality of photosensitive pixels, optically coupled to the scintillator array (202), and a current-to-frequency (I/F) converter (302). The I/F converter (302) includes an integrator (304) that integrates charge output by a photosensitive pixel during an integration period and generates a signal indicative thereof and a comparator (310) that generates a pulse when the generated signal satisfies predetermined criteria during the integration period. A reset device (316) resets the integrator (304) in response to the comparator (310) generating a pulse. Circuitry (320, 324) samples the generated signal at a beginning of the integration period and/or at an end of the integration period and generates quantized digital data indicative thereof. Logic (322) estimates the charge at the input of the integrator (304) based on the generated digital data.