tft how to connect a flat panel detector to a computer

The core part of DDR is the flat panel detector. It can be summarized as a detector that uses semiconductor technology to convert X-ray energy directly into an electrical signal to produce an X-ray image. The flat panel detector can replace all types of X-ray detectors nowadays, such as TV image enhancement systems. Its most outstanding feature is that the output is a high-quality digitized image. In the direct conversion type, its manufacturing transfer function (MTF) characteristics are better than image screen systems, and the sensitivity is comparable to that of TV enhancement systems. The development and further improvement of flat panel detectors will gradually replace the traditional X-ray detection devices. 1, the type of flat panel detector can be broadly divided into CCD type and amorphous silicon type, amorphous type. ccd-type flat panel detector is the main principle of the optical signal from the detector within the ccd acceptance, read out and the formation of digital images. 2, amorphous silicon type flat panel detector, the core of which is composed of amorphous silicon and thin film transistor matrix board, each unit of the matrix board contains a storage capacitor and amorphous silicon field effect tube. The entire digital matrix is encapsulated in a box like a "sheet folder", which consists mainly of a scintillation layer or layers, a matrix board and glass substrate, readout lines, etc.. Its good density and spatial resolution represent the main direction of current development. Cesium iodide (CsI) has high X-ray reception and visible photon yield. Because cesium has a high atomic number, it is the best material of choice for X-ray receivers, so this metal is very suitable for incoming X-rays. It takes 20 to 25 eV to produce each photon. Admixture of cesium CsI excites light at 550 nm, which is the peak of amorphous silicon spectral sensitivity. 3, as a photoconductive material, there are two reasons: ① photoresistor itself has a high resolution characteristics; ② with a thicker photoconductive absorber layer, you can get a higher X-ray sensitivity. X-ray energy can be directly converted into electrical signals. The electron-hole pairs generated by the photoconductive layer after being irradiated by X-rays are separated by an electric field at an offset voltage of 6KV, and are collected by each pixel unit and converted into the data of the X-ray digital image. The matrix plate consists of a thin-film transistor (TFT) storage capacitor and collector with an amorphous silicon layer deposited about 500 μm thick. the many pixels (139 × 139 μm) are arranged as a two-dimensional matrix with gated lines by rows. the size of the TFT pixels determines directly the spatial resolution of the image, and each pixel has a charge-receiving electrode, a signal storage capacitor, and a signal transducer. signal storage capacitor and signal transmitter, which is connected to the scanning circuit through a data network. Finally, the digital signal is read by the readout circuit and reduced to an image. Amorphous silicon is the most ideal material for X-ray receivers because amorphous silicon is immune to radiation damage. These are the main components of the flat panel detector structure. The flat panel detector and the X-ray bulb tube form the main part of direct digital imaging. The other part is the operation, quality control and post-processing part. Most of the work is performed by a computer. The functions of the main processor in real time include: offset correction and gain; black level clamping; smudge interpolation; frame accumulation and homogenization. As for the post-processing of images, it can be done by using the auxiliary processor, including X-ray exposure control, graphical windowing of image data, conversion of scans to conventional mode, finding directories, noise reduction variable recursive filtering, etc. Optimal performance requires low noise, wide dynamic range and fast response time. The DDR imaging system can be combined with the user's existing X-ray machine to provide digital X-ray image data. Other auxiliary equipment are: scanning controller, system controller, image monitor. Scanning controller is mainly composed of computer-controlled matrix scanning circuit, recovery circuit and scan data conversion device. The system scanner is a computer host system, including operating procedures, image processing programs, image storage, printing network management. The image monitor displays photographic images to provide staff with photographic quality references. The conversion of X-rays into electrical signals can be accomplished by both direct and indirect methods. In the direct conversion method, voltage is applied to the layer as a photoconductor, and the energy of X-rays is directly converted into electrical signals. In the indirect conversion method, the X-rays are first converted into a light signal by a scintillator, which is then converted into an electrical signal by a photodiode. Flat-panel detectors can be converted in both ways, and their main difference lies in their manufacturing structure. The above two types of detectors have their own advantages and disadvantages. CsI scintillator layer due to the crystal structure of the relationship between the transmission of the signal at the same time the inevitable light scattering occurs, the absorption rate has decreased, but the final image quality is not great. Its high quantum detection efficacy (DQE) allows high quality images to be obtained at lower dose exposures. Due to the fast imaging, it can be used in the fields of fluoroscopy and time subtraction, which greatly increases the scope of use of X-ray examination. And as a photoconductor, it can directly convert optical signals into electrical signals, avoiding the occurrence of scattering. However, the absorption rate of X-ray is low, and the image quality cannot be guaranteed well under low dose conditions. And the layer is sensitive to temperature, the use of conditions are limited. Flat-panel detectors for DR and DDR can be easily applied to current conventional radiographic equipment and are fixed to vertical chest film holders or filters on flat beds. The image is displayed a few seconds after exposure, without the need to carry the cassette back and forth; the system itself is fully solidified, without any mechanical movement. At the same time in the exposure of the operating room monitor can be displayed on the photographic image, the staff can make a judgment on the quality of the projection, shorten the examination time, to avoid the technical reasons for the patient's repeat examination