Servoing X-ray Source via MOS Sensor Feedback
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Solution Overview
Problem
Existing digital radiography systems face challenges in controlling X-ray sources to prevent pixel overexposure or underexposure, leading to degraded signal-to-noise ratios and impaired image quality, especially in dental radiography where dose sensors fail to accurately report radiation levels across different tissue types.
Innovation Solution
A method for servoing an X-ray source using a MOS-type image sensor with separate read and refreshment commands, where X-ray emission is controlled based on image acquisition characteristics derived from reading signals of multiple pixels, allowing for optimal exposure adjustment without disturbing pixel integration, and using a computer to compare these characteristics with preset values to interrupt exposure when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dose sensors are used to control X-ray source, then radiation dose can be monitored, but local overexposure or underexposure cannot be prevented due to incorrect reporting in specific tissue locations
Solution Approach 1:
The patent divides the sensor surface into multiple pixels, each independently measuring radiation dose locally. This segmentation allows the system to detect overexposure or underexposure in specific regions without being affected by incorrect readings from dose sensors placed in problematic locations. Each pixel provides independent dose information, enabling localized control of X-ray exposure.
Solution Approach 2:
The patent implements a feedback mechanism where the control unit continuously monitors pixel readings during X-ray exposure and adjusts the X-ray source emission accordingly. When a pixel detects overexposure or underexposure, the control unit modifies the emission to correct the imbalance, ensuring optimal exposure across the entire sensor surface.
2Device complexity
If sequential reading is used for CMOS pixels, then fewer electrical conductors are needed, but pixel overexposure or underexposure control becomes more difficult
Solution Approach 1:
The patent performs preliminary refreshment of pixels before reading, ensuring that pixels are in a known state ready for accurate measurement. This preliminary action allows the system to maintain exposure control precision while using sequential reading to reduce electrical connection complexity.
Solution Approach 2:
The patent dynamically adjusts the timing between refreshment and reading operations based on the specific pixel being accessed. By optimizing the sequence and timing of these operations, the system achieves both reduced electrical connection complexity and precise exposure control.
3Ease of operation
If X-ray emission continues until fixed time, then simple control is maintained, but pixel overexposure occurs when tissue density varies
Solution Approach 1:
The patent uses feedback from pixel readings during the exposure process to dynamically adjust X-ray emission timing. Instead of fixed-time exposure, the system monitors actual pixel saturation levels and stops emission when optimal exposure is achieved, preventing overexposure in dense tissues while ensuring sufficient exposure in less dense areas.
Solution Approach 2:
The patent transitions from static, fixed-time exposure control to dynamic exposure control that adapts to varying tissue densities. The system adjusts emission duration and intensity in real-time based on feedback from pixel readings, achieving uniform exposure across different tissue types.
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 enables precise control of radiation dose, preventing local overexposures and underexposures, optimizing exposure for specific tissue types, and reducing the radiation dose to patients while maintaining image quality.
Implementation Method 1
The sensitive surface is linked to a scintillator that converts the X-rays received by the sensor into radiation whose wavelength is compatible with the pixels' sensitivity spectrum
Implementation Method 2
Each pixel has an internal capacity, charged (or discharged, respectively) during a refreshment step, and a photosensitive diode that, under the effect of radiation, gradually discharges (or charges, respectively) the capacity
Data Source
AI summary
The invention relates to a radiographic device and method of servoing an X-ray source (800) in a radiography device comprising a MOS-type image sensor (810) with pixels provided with separate read and refreshment commands, respectively, in which, during a radiography operation, read commands of a plurality of image sensor pixels are called repeatedly, while maintaining a source of X-rays power-supplied, so as to establish, in response to each reading, at least one image acquisition characteristic, and in which the emission of X-rays is interrupted when the image acquisition characteristic corresponds to a preset image acquisition characteristic.