Flat panel detector is a key device in the field of modern medical imaging, which can convert the energy of X-rays into electrical signals and generate digital images for diagnosis. According to the different materials and working principles, flat panel detectors are mainly divided into two types: amorphous selenium flat panel detectors and amorphous silicon flat panel detectors.
Amorphous selenium flat panel detector
The amorphous selenium flat panel detector adopts a direct conversion method, and its basic components include a collector matrix, a selenium layer, a dielectric layer, a top electrode, and a protective layer. The collector matrix is composed of thin film transistors (TFTs) arranged in an array element manner, which are responsible for receiving and storing electrical signals converted by the selenium layer. The selenium layer is an amorphous selenium semiconductor material that generates a thin film of approximately 0.5mm thickness through vacuum evaporation. It is highly sensitive to X-rays and has high image resolution capabilities.
When X-rays are incident, the electric field formed by connecting the top electrode to the high-voltage power supply causes the X-rays to pass through the insulating layer vertically along the direction of the electric field and reach the amorphous selenium layer. The amorphous selenium layer directly converts X-rays into electrical signals, which are stored in the storage capacitor. Subsequently, the pulse control gate circuit turns on the thin film transistor, delivering the stored charge to the output of the charge amplifier, completing the conversion of the photoelectric signal. After further conversion by a digital converter, a digital image is formed and input into a computer, which then restores the image on a monitor for direct diagnosis by doctors.
Amorphous silicon flat panel detector
The amorphous silicon flat panel detector adopts an indirect conversion method, and its basic structure includes a scintillator material layer, an amorphous silicon photodiode circuit, and a charge readout circuit. Scintillation materials, such as cesium iodide or gadolinium oxysulfide, are located on the surface of the detector and are responsible for converting attenuated X-rays that pass through the human body into visible light. The amorphous silicon photodiode array under the scintillator converts visible light into electrical signals, and the stored charge of each pixel is proportional to the intensity of the incident X-ray.
Under the action of the control circuit, the stored charges of each pixel are scanned and read out, and after A/D conversion, digital signals are output and transmitted to the computer for image processing, thereby forming X-ray digital images.
In summary, there are differences in the composition and working principle between amorphous selenium and amorphous silicon flat panel detectors, but both can efficiently convert X-rays into electrical signals, generate high-quality digital images, and provide strong support for medical imaging diagnosis.
（reference resources:https://www.chongwuxguangji.com/info/muscle-3744.html）
Post time: Dec-03-2024