CT Detector Residual Charge Circuit for Spatial Accuracy
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Solution Overview
Problem
Current CT scanner detector arrays face limitations in spatial accuracy during low signal, low-dose imaging due to the use of current to frequency converters, which require increased circuitry area, cost, and power, and result in data skewing that complicates accurate signal processing.
Innovation Solution
Incorporating a residual charge collection circuit electrically coupled to the current-to-frequency converter, which stores charge from the last pulse of an integration period to the end of the period, allowing for accurate measurement and elimination of spatial skewing without increasing circuit complexity or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current to frequency converter is used as the A/D converter, then the spatial accuracy is improved in low signal, low-dose imaging procedures, but the circuitry area, cost and power requirements increase
Solution Approach 1:
The patent extracts the residual charge measurement function from the main integration circuit by adding a separate residual charge collection circuit. This circuit specifically captures and measures only the residual charge portion, allowing the main integration circuit to continue functioning without modification. The extraction of this specific function enables accurate residual charge measurement while maintaining the original circuit architecture, thus improving spatial accuracy without significantly increasing overall circuit complexity.
Solution Approach 2:
The patent introduces a residual charge collection circuit as an intermediary component between the current to frequency converter and the final signal processing stage. This intermediary circuit captures the residual charge that would otherwise be lost, converts it to a measurable signal, and combines it with the main integration signal. This mediator enables accurate total charge measurement by bridging the gap between the pulse train output and the integration period boundaries.
2Reliability
If data re-alignment is performed to compensate for charge overlap, then signal to noise is improved, but spatial accuracy is reduced due to skewing of data in time
Solution Approach 1:
The patent performs preliminary measurement of the residual charge at the end of each integration period before the next integration period begins. By capturing and storing the residual charge value in advance, the system eliminates the need for post-processing re-alignment operations. This preliminary action ensures that the total charge measurement is complete and accurate from the start, preventing temporal skewing while maintaining signal-to-noise improvement.
Solution Approach 2:
The patent implements a feedback mechanism where the residual charge measurement from the end of each integration period is fed back into the total charge calculation for that period. This feedback loop ensures that the complete charge information is available for accurate spatial positioning, eliminating the need for compensatory re-alignment operations that would introduce temporal skewing. The feedback approach maintains both signal-to-noise ratio and spatial accuracy simultaneously.
3Measurement precision
If additional circuitry is added to overcome spatial skewing, then spatial accuracy is improved, but cost and power requirements increase
Solution Approach 1:
The patent merges the residual charge collection function with the existing current to frequency converter circuitry by electrically coupling the residual charge collection circuit to the converter's output. This merging approach allows the residual charge measurement to be performed using the same operational framework and power supply as the main integration circuit, rather than requiring a completely separate high-power system. The combined approach achieves improved spatial accuracy while minimizing additional power consumption.
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 spatial accuracy in CT imaging by accurately measuring total charge without the need for additional circuitry, enabling precise data collection coincident with integration period ends and reducing the effects of data skewing, particularly beneficial for fast KV x-ray tubes.
Implementation Method 1
a current-to-frequency converter configured to convert the signal into a pulse train having a frequency indicative of a charge collected during an integration period
Implementation Method 2
The residual charge collection circuit is configured to store charge collected by the current-to-frequency converter for the integration period from a last pulse generated by the current-to-frequency converter to an end of the integration period
Data Source
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AI summary
A detector array (112) of an imaging system (100)includes a radiation sensitive detector (202/204/206) configured to detect radiation and generates a signal indicative thereof and electronics (208) in electrical communication with the radiation sensitive detector. The electronics include a current-to-frequency converter (300) configured to convert the signal into a pulse train having a frequency indicative of a charge collected during an integration period. The electronics further include a residual charge collection circuit (322) electrically coupled to current-to-frequency converter. The residual charge collection circuit is configured to store charge collected by the integrator for an end portion of the integration period that does not results in a pulse of the pulse train, utilizing much of the electronics already in the current-to-frequency converter electronics.