Virtual Pulse Injection for Gamma System Count Loss Correction
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Solution Overview
Problem
Existing count loss correction methods in nuclear imaging systems, such as SPECT, are inaccurate due to time-invariant and use-case variant dead time phenomena, leading to undercounting of events and reduced accuracy in activity estimation.
Innovation Solution
The method involves injecting a virtual gamma-event signal into the discriminator's event control logic to directly measure count loss without causing additional discrimination, using a virtual pulse injection logic that checks the discriminator's state to determine its ability to discriminate events, and correcting for count loss based on this information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If empirical look-up table methods are used for count loss correction, then the system is simple to implement, but the accuracy of count loss correction deteriorates due to time-invariant and use-case variant dead time phenomena
Solution Approach 1:
The patent creates a virtual copy of the discriminator's decision logic that runs in parallel without affecting actual event processing. This virtual discriminator models the dead time behavior and generates correction factors, allowing accurate dynamic correction without interfering with the primary detection path.
Solution Approach 2:
The patent introduces a virtual pulse generator as an intermediary component that simulates incoming events to probe the discriminator's dead time characteristics. This intermediary allows measurement of system response without introducing actual counting errors, bridging the gap between theoretical models and real system behavior.
2Measurement precision
If actual pulse generators are used to test discriminator capability, then the system can measure dead time directly, but the injected pulses interfere with normal counting and cause additional count loss
Solution Approach 1:
The patent uses a virtual copy of the discriminator logic rather than injecting actual pulses into the physical system. This virtual modeling approach allows direct measurement of dead time effects without introducing real counting errors, as the virtual discriminator processes simulated events separately from the actual detection chain.
Solution Approach 2:
The patent replaces the physical pulse injection mechanism with a computational model of the discriminator's decision logic. This substitution eliminates the need for physical pulse generation and injection, using software-based simulation to measure dead time characteristics without mechanical or electronic interference with the actual counting process.
3Measurement precision
If the discriminator processes additional test pulses to measure count loss, then direct measurement is possible, but the processing time increases and real-time correction capability deteriorates
Solution Approach 1:
The patent creates a virtual duplicate of the discriminator's decision-making logic that operates in parallel with the actual discriminator. This virtual copy processes simulated events at high speed without the overhead of physical pulse processing, enabling real-time measurement of dead time effects and generation of correction factors.
Solution Approach 2:
The patent performs preliminary virtual testing of discriminator capability using simulated events to determine dead time characteristics before processing actual patient data. This preliminary action allows the system to pre-calculate correction factors that can be applied in real-time during actual imaging, separating the measurement process from the diagnostic process.
Data Source
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AI summary
For count loss correction (507), the capability of the discriminator (114), measured periodically, to detect an event is identified (503). Rather than inserting an actual event or a signal emulating an actual event for discrimination, the capability to discriminate is tested by a virtual injection (501). The count loss may be directly measured without causing extra actual discrimination by the discriminator (114). Direct measurement with virtual testing may avoid loss of accuracy due to time and use-case variation.