CT Scanner Signal Processing Delta Data Correction
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Solution Overview
Problem
In stereo tube computed tomography (CT) scanners, residual charge from one sampling interval can erroneously contribute to the next interval, known as Delta Data, due to misalignment of pulses with sampling interval boundaries, leading to corrupted charge measurements.
Innovation Solution
The system includes processing electronics that calculate a first contribution for pulses up to the last pulse in a sampling interval and estimate a second contribution based on charge decay, using a reset mechanism to clear the integrating circuitry before the next interval, thereby mitigating Delta Data by determining the missing charge through exponential decay estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current-to-frequency converter generates pulses based on photodiode output current, then the signal is converted to a measurable pulse train, but the last pulse may not align with the sampling interval boundary causing residual charge to carry over to the next interval
Solution Approach 1:
The patent applies preliminary action by resetting the integrating circuitry before the next sampling interval begins. The reset mechanism proactively clears any residual charge from the previous interval, preventing it from contaminating the next measurement. This advance reset ensures that each sampling interval starts with a clean state, eliminating the Delta Data problem where residual charge would otherwise carry over and corrupt subsequent measurements.
2Quantity of substance
If the integrating circuitry accumulates charge throughout the entire sampling interval, then complete charge information is captured, but residual charge from the previous interval contaminates the next interval measurement
Solution Approach 1:
The patent applies segmentation by dividing the charge accumulation process into distinct phases: an integration phase where charge is accumulated from the photodiode output, and a reset phase where the integrating circuitry is cleared. This segmentation is timed such that integration occurs during the sampling interval while the reset occurs just before the next interval begins. The segmentation ensures complete charge capture during integration while preventing residual charge contamination through timely clearing.
Solution Approach 2:
The patent applies discarding and recovering by deliberately discarding (resetting) the residual charge in the integrating circuitry before the next sampling interval begins. The reset mechanism discards any remaining charge from the previous interval, preventing it from being recovered and erroneously added to the next measurement. This controlled discarding ensures that only charge from the current sampling interval is measured, eliminating cross-interval contamination.
3Loss of information
If pulses are generated continuously based on signal amplitude, then the signal information is preserved in pulse frequency, but the discrete pulse timing may not align with sampling boundaries causing measurement errors
Solution Approach 1:
The patent applies feedback by using the pulse train information to determine the charge for each sampling interval. The current-to-frequency converter generates pulses whose frequency reflects the signal amplitude, and this pulse information feeds back into the charge determination process. By counting pulses or measuring their frequency within each sampling interval, the system accurately recovers the charge information while the reset mechanism ensures clean separation between intervals, preventing timing misalignment errors.
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 accurately determines the signal for each sampling interval by separating and correcting for residual charge, ensuring precise charge measurement and reducing afterglow artifacts in subsequent intervals.
Implementation Method 1
The scintillator absorbs radiation and produces light indicative of the absorbed radiation
Implementation Method 2
the photodiode receives the light and produces a signal such as an electrical current or voltage indicative of the light
Data Source
AI summary
An imaging system includes at least one radiation generating component (210) that alternately emits different radiation that traverse an examination region and a common detector (214) that detects radiation that traverses the examination region and generates a signal indicative thereof. Pulse generating circuitry (304) generates a pulse train, including a plurality of pulses, with a frequency indicative of the signal for the at least one radiation generating component (210) for a sampling interval. Processing electronics (220) determine an approximation of the signal for one of the at least one radiation generating components (210) for the sampling interval based on a number of pulses in the pulse train for the sampling interval and charge of the pulses in the pulse train.