What is the difference between amorphous silicon and amorphous selenium materials in C-arm flat panel detectors?

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The flat panel detector is one of the important components of the C-arm X-ray machine. Its function is to convert the image signal generated by the X-rays emitted by the C-arm penetrating the human body into a digital image that can be stored and processed.

The C-arm flat panel detector can be divided into amorphous silicon and amorphous selenium. The core of amorphous silicon flat panel detectors is a matrix board composed of amorphous silicon and thin-film transistors, whose good density and spatial resolution represent the main direction of current development. The amorphous selenium flat panel detector uses selenium as a photoconductive material, which can directly convert light signals into electrical signals, thereby avoiding scattering.

The following will introduce the differences between the two, which has important guiding significance for hospitals to choose C-arm equipment reasonably.

1、 Structural differences

The structure of the amorphous silicon flat panel detector is mainly composed of a scintillator and a photosensitive body (an amorphous silicon layer with photodiode effect) integrated together, and a TFT array; The structure of the amorphous selenium flat panel detector is mainly composed of an amorphous selenium layer and a TFT array.

2、 The principle of A/D conversion is different

The principle of amorphous silicon is that after X-ray exposure, the scintillator converts the photons of the X-ray into visible light. Then, the amorphous silicon layer converts the visible light into an electrical signal through the action of a photodiode, detects the array through TFT, and finally obtains a digital image through A/D conversion; The working principle of amorphous selenium is that the amorphous selenium layer directly generates an electrical signal after X-ray exposure, which is detected by a TFT detection array and then converted into a digital image through A/D conversion.

3、 The difference between the fluorescent material layer and the detection element array layer

Generally speaking, the image clarity and sharpness of amorphous selenium plates are better than those of amorphous silicon plates.

4、 Differences in usage costs

The amorphous selenium flat panel detector has very high requirements for the working environment during use, with a shorter service life compared to amorphous silicon flat panels, a higher failure rate, and higher maintenance costs than amorphous silicon flat panel detectors.

Cesium iodide amorphous silicon flat panel

Summary: The imaging effect of amorphous selenium detectors is better than that of amorphous silicon, with clearer and sharper images. However, the technology of amorphous selenium flat panel detectors is not yet stable, which has very high requirements for the usage environment and high maintenance costs. Therefore, currently, amorphous silicon flat panel detectors are still the mainstream in the market. For example, the domestically produced 3D flat panel C-arm PLX7500 series, which has received widespread attention in recent years, uses a 30cm x 30cm cesium iodide amorphous silicon flat panel for its dynamic flat panel detector, and is produced by the original factory of Puai Medical. Puai Medical has developed into one of the few core component manufacturers in China, and currently has independent research and development and production capabilities for ball tubes and high-pressure generators. The company ranks first in the sales ranking of C-shaped arms in 2022.

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