Radiation Imaging Device Synchronization for Energy Subtraction
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Solution Overview
Problem
In radiation imaging apparatuses using the energy subtraction method, variations in time from X-ray emission to signal transfer can lead to differences in energy and dose between frames, resulting in reduced accuracy of energy subtraction, especially when capturing videos of moving objects.
Innovation Solution
A radiation imaging apparatus with a pixel array and readout circuit that includes sample-and-hold circuits and a processing unit to determine and control the timings of sampling-and-holding, ensuring synchronization with radiation emission to minimize variations in signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple radiation images are captured with time intervals for energy subtraction method, then bone images and soft tissue images can be obtained, but artifacts occur due to object movement between capture intervals
Solution Approach 1:
The patent applies periodic action by capturing multiple radiation images at specific time intervals with different energy levels (kVp values). The system periodically switches between different energy levels (e.g., 80 kVp and 140 kVp) to capture images that can be processed through energy subtraction, while managing the timing to minimize motion artifacts.
Solution Approach 2:
The patent uses preliminary action by implementing a sample-and-hold circuit that captures and holds the signal at a specific timing relative to the X-ray emission. This preliminary signal capture ensures that the timing variation between X-ray emission and signal transfer is minimized and consistent across multiple images, reducing artifacts before the energy subtraction processing occurs.
2Adaptability or versatility
If tube voltage is changed between first kV value and second kV value for dual energy imaging, then first sub-image and second sub-image can be obtained, but reading of integrated first signal and integration of second signal are performed in parallel causing timing variations
Solution Approach 1:
The patent implements preliminary action by using a sample-and-hold circuit that captures the signal at a predetermined timing relative to the X-ray emission pulse. This hold circuit maintains the captured signal level throughout the dual-energy imaging sequence, ensuring that both the first sub-image (at first kV value) and second sub-image (at second kV value) are sampled with consistent timing, thereby eliminating timing variations during parallel signal processing.
3Measurement precision
If images are captured at time intervals of several seconds for still images or 100 milliseconds for normal videos, then energy subtraction processing can be performed, but objects moving quickly cannot be imaged without artifacts
Solution Approach 1:
The patent applies periodic action by using pulsed X-ray emission with specific timing patterns. The system emits X-rays at controlled intervals with different energy levels, and the sample-and-hold circuit synchronizes signal capture with these pulses. This periodic, synchronized approach allows for faster capture sequences that can handle moving objects while maintaining the energy subtraction capability.
Solution Approach 2:
The patent uses preliminary action by pre-synchronizing the sample-and-hold circuit timing with the X-ray emission pulses. This ensures that signals are captured at consistent, predetermined intervals regardless of object motion speed, allowing the system to image moving objects at higher frame rates (e.g., 100 milliseconds or faster) while maintaining energy subtraction accuracy through consistent timing.
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 reduces variations in signal sampling and holding times, enhancing the accuracy of energy subtraction and reducing artifacts in video frames, particularly for moving objects like the heart.
Implementation Method 1
each of the plurality of pixels includes a conversion element configured to convert a radiation into an electrical signal
Data Source
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AI summary
A radiation imaging apparatus includes a pixel array including a plurality of pixels, and a readout circuit configured to read out a signal from the pixel array, each of the plurality of pixels including a conversion element configured to convert a radiation into an electrical signal, and a sample-and-hold circuit configured to perform sampling-and-holding a plurality of times on a signal from the conversion element in response to the radiation. The radiation imaging apparatus further includes a processing unit configured to perform processing of determining timings of the plurality of times of the sampling-and-holdings based on information about temporal change in radiation energy of the radiation obtained based on a signal read out by the readout circuit, and a control unit configured to perform control so that the plurality of times of sampling-and-holdings is performed by the sample-and-hold circuit at the timings determined by the processing unit.