Radiation Imaging Pixel Array Reset Timing for Energy Subtraction
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Solution Overview
Problem
The energy subtraction method in radiation imaging is hindered by the need for prolonged radiation irradiation times, which can result in artifacts when imaging moving objects, such as the heart, due to the time required for capturing and processing multiple images at different energy levels.
Innovation Solution
A radiation imaging apparatus with a pixel array that includes conversion elements and reset portions, where the reset operation is avoided during the periods of radiation exposure at different energy levels, allowing for simultaneous capture and processing of images without losing radiation information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the reset operation is performed after integration of the first signal to enable parallel readout and integration, then the time interval for capturing two images is shortened, but radiation is wasted during the reset period which does not contribute to imaging
Solution Approach 1:
The conversion element performs integration of radiation signals during the first period, and the sample and hold circuit captures this integrated signal before the reset operation. This preliminary action allows the radiation information to be preserved and held, enabling the reset to occur without losing the accumulated radiation data, thus eliminating radiation waste during the reset period.
Solution Approach 2:
The sample and hold circuit creates a copy of the integrated signal from the conversion element. This copied signal is then read out while the conversion element is being reset, allowing parallel operation without data loss. The copying mechanism decouples the readout process from the integration process, eliminating the need to wait for reset completion before reading the signal.
2Reliability
If the radiation irradiation time is shortened to suppress object movement influence, then motion artifacts are reduced, but the reset operation still causes wasted radiation time
Solution Approach 1:
The useful action of radiation detection is maintained continuously by overlapping the integration period with the readout period. The sample and hold circuit enables the readout to occur during the second period when radiation is being detected again, ensuring that the detection process continues without interruption and no radiation time is wasted on reset operations.
Solution Approach 2:
The system uses periodic radiation emission with alternating first and second periods. During the first period, the conversion element integrates radiation while the sample and hold circuit reads out the previous signal. During the second period, the conversion element integrates new radiation while the first signal is being read out. This periodic action pattern allows continuous useful radiation detection without waste during reset.
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 radiation irradiation time and minimizes artifacts from object movement, enabling more accurate and efficient energy subtraction imaging, particularly for fast-moving subjects.
Implementation Method 1
a conversion element that converts radiation into an electrical signal
Data Source
AI summary
A radiation imaging apparatus that obtains a radiation image by an energy subtraction method. Each pixel includes a conversion element that converts radiation into an electrical signal and a reset portion that resets the conversion element. Each pixel performs an operation of outputting a first signal corresponding to an electrical signal generated by the conversion element in a first period, and an operation of outputting a second signal corresponding to an electrical signal generated by the conversion element in the first period and a second period. Radiation having first energy is emitted in the first period, and radiation having second energy is emitted in the second period. In each pixel, the reset portion does not reset the conversion element during a period that includes the first period and the second period.