Comparison of DR and DF--Low Dose DR supplier

Comparison of DR and DF

#Digital radiography# In the 21st century, digital technology and network technology rapid development, businesses are speeding up the pace of going digital, hospitals are the best way to improve the quality of medical imaging it is to make digital imaging. In the field of radiology, we have CT, MRI, DSA and other digital gastrointestinal digital medical equipment; X-ray imaging technology in recent years has accelerated the pace of march to digital. FPD is the second CR came into being after the all-digital X-ray imaging technology revolution is another key achievements and progress. So the birth of FPD known as the following image intensifier (II-VT) came 25 years to the most significant technological breakthroughs in the field of X-ray.

Characteristics of digital images

It refers to a fully digital image in a regular set of digital shape pattern, its features are: gray dynamic range, high density resolution, good linearity, rich layers, post-acquisition mode can be processed. No matter what way, those who can digital technology used in computer processing, storage, flat X-ray photography image displayed is called digital radiology (digital radiology, DR). Obtaining digitized images: X line of digital images that can be obtained through the following four ways or transfer: (1) Film Digitizer (Film Digitizer), such as film DR field - scanner system; (2) Computer X-ray photography CR ( Computed Radiography); (3) non-direct conversion technology (Indirect Conversion Technology), the imaging device is the use of this type of X-ray image by X-ray film or image intensifier is converted to a digital signal methods, such as a scintillator and digital -CCD X-ray (DigitalX-ray Flouoroscopy, DF) mechanism in the field of digital IIT system; (4) direct conversion technology (Direct Conversion Technology), is the second CT, MRI, CR after another new video imaging technology, including flat-type , linear array detector scan imaging [1, 4-12]. The first three are indirect, the fourth approach is a direct way.

Flat panel detector (FPD)

Also known as the digital detector, which consists of a scintillator, thin-film photovoltaic diode array and a thin film transistor (TFT) array of, X-ray through the reflective layer to be absorbed by the scintillator, excited electrons and holes on the applied electric field Motion is transmitted to the lower layer and the photodiode, converted into an electric signal, junction capacitance staging charge. The electrical pulses (about 13V) is applied to the gate TFT, TFT is turned on, put the charge stored in the drain electrode to read out the data at the source (read) line, after the data readout amplifier (charge amplifier) ​​Enlarge , and further processing by the A / D converted digital image signals formed corresponding pixel; i.e., capable of receiving the X-ray signal is directly converted into a digital signal. FPD arranged in diode array, each corresponding to a pixel TFT, TFT determines how much the number of pixels, high level of integration to ensure the small distance between the centers of adjacent pixels. FPD spatial resolution that is transmitted mainly by the modulation function (modulation transfer function, MTF) decided by the size of the pixel TFT to ensure and enhanced. FPD high radiation absorption rate, conversion rate and high signal transmission capacity, the overall high radiation sensitivity characteristic, effective gain correction and dark current correction, creating a DR system's high dynamic range (2000: 1, 4000: 1 or more high), low density excellent resolution performance, quality and low dose imaging. In short, FPD represented the many advantages of the film outside of each high performance digital imaging X-ray detector: quantum efficiency Doses small, large dynamic range, latitude photographing conditions, good linear detector characteristic curve, can truthfully Human density structure, image density, high resolution, rich diagnostic information and general advantages of digital X-ray imaging system --- can facilitate a variety of image processing, analysis, measurement, best display, imaging extensions, no film preservation, energy and a variety of diagnostic tools and Infiltrating the resulting image even merge complementary treatment can be achieved through digital network digital video transmission between departments or between different places and so on, but also has other advantages unmatched system.

FPD-DR system

DR (Digital X-ray radiography) X-ray is the new darling of the field, it's the birth of making the majority of the high-tech X-ray workers saw the enormous advantages and a bright future.

DR imaging system produces mainly four aspects: (1) X ray detector; (2) the digitization process, which generated or read from the input signal to a digital image; (3) image processing systems; (4) the image display record

And traditional X-ray screen - film imaging systems compared, FPD-DR system has the following advantages: space (1) images and high resolution and low-contrast identification rate. Digital image processing, greatly improving the image quality, it has a richer, delicate diagnostic information. (2) imaging the dynamic range (10 times the available conventional systems), good linearity. Data shows that cesium iodide digital board GE's non-splicing film systems using quantum capture efficacy (detective quantum efficiency, DQE) up to 60% or more (while DQE traditional film system is only about 20%), low contrast observation capacity increased by 45% to obtain the same image quality of X-ray dose savings of up to 60% or more, the film anteroposterior chest X-ray dose of just 1-3mAs. DR also has a variety of digital image processing, image processing through different methods, to meet a variety of different diagnostic needs. (3) The afterglow small, to do rapid acquisition. FPD in a large number of pixels in the image data stored in the working efficiency of DR chest GE system is equivalent to the efficiency of 2.6 ordinary film machine, complete and lateral chest X-ray taken only 2 .18min, and general equipment needs 6. 05min; image from exposure to full-screen display on the monitor just 5s. (4) reduce the exposure dose. FPD due to the high sensitivity, wide sensitivity range, you can increase the tolerance of photography conditions while reducing dose X-ray photography, X-ray dose than conventional X-ray photography to be lower by 10% to 30% [2]. (5) save resources and improve efficiency. Because of greatly reducing the film using traditional film, reducing the remake, washing, thus reducing the workload of the technical staff, but also reduces the washing machine, medicine, film management to improve work efficiency. (6) high DQE, low dose and small afterglow characteristics, DR can make fast and efficient machine for cardiac signal acquisition. Digital (7) of the image into the hospital network provides a digital platform. Since taking into account the requirements of image quality and network transmission, with the standard DICOM (medical digital communications protocol) transmission, DICOM storage, DICOM print, the connection RIS (Radiology Information System) and HIS (hospital information system) it is very easy to make PACS ( picture archiving and communication systems) as possible.

FPD-DR imaging system is fixed, not with the original X-ray machine used in combination. It can directly display images, imaging speed, easy to operate, eliminating the hard work of carrying cassette operation, improve work efficiency. The great potential of the imaging system, the first of its DQE high, wide dynamic range, and the image signal contains more gray, window technology can be applied to enhance the display of information in different gray stages. X-rays directly into electrical signals, avoiding the fluorescence scattering loss of detail caused by sharp, so that the image sharpness and high resolution. FPD-DR resolution limit depends on the size of the TFT (pixel), the smaller the pixel resolution of the advantages are more prominent.

FPD-DF system

FPD fluoroscopy system if used, it can order a when the four, which replaces the image intensifier FPD, optical systems, cameras and ADC, to avoid the above-mentioned every aspect caused by distortion, noise and resolution decreases.

A long time, the main use of IIT + optocoupler + imaging device to get real-time X-ray image signal, multi-use TV camera tube past as an imaging device to obtain an analog image signal, after analog-digital conversion can also be converted into a digital image. Using CCD imaging device, each unit output signal that is corresponding image pixel signals Serve quantized digital information. This traditional DF system signal detection system, bulky, clinical application impede or permit doctors to give patients a lot of the required image angle at the time. Although CCD compact, but because it is not satisfied with the work at low brightness, nor from IIT. Multi-class system signal format conversion, signal loss and noise introduced many links, DQE will be reduced. By the imaging device and IIT and other factors, the differential rate system space restrictions caused by the differential rate is poor. Meanwhile, IIT and the front surface optics are non-ideal cause image distortion. IIT also susceptible to magnetic fields. Small size, light weight, excellent performance, low environmental requirements of FPD, IIT system is an ideal alternative.

FPD DF system for imaging, fluoroscopy generated to meet at 26 to 30 frames per second. Generates a frame image in a very short time interval to complete the exposure, a large number of pixels is read out line by line in the signal data, various corrections in real time, real-time correlation recursive filtering steps, which requires a high FPD sufficient time resolution and sufficiently small hysteresis characteristic.

In order to ensure good image quality perspective, FPD-noise ratio must be high enough level. This requires a lower tube voltage, tube current perspective small conditions can still get an image in a short time exposure image signal intensity and low background noise, the use of DF FPD stronger signal, lower noise are demanded only FPD for DR is more prominent and harsh. Under certain conditions, FPD temporal resolution DF meet requirements; such as by optimizing the design and manufacturing processes, the use of the larger size of the pixel or the adjacent small binning, FPD image size restrictions and other measures to ensure that generates a very short time frame performance meets or exceeds the image intensifier fluoroscopy imaging system image. DR uses FPD is greater technological progress, trying to inherit and carry forward the excellent performance FPD DR purposes but need the right amount at the expense of some technical indicators, focusing on strengthening and DF meet product requirements.

DF uses the frequency characteristics of FPD than smaller pixel size is only for DR purposes FPD badly, but still has optimum MTF characteristics. Higher FPD-DF of DQE. Small hysteresis, effective memory effect correction, very strict noise suppression to keep the use of FPD DF inherited the excellent characteristics of linearity DR uses the FPD. DF FPD uses only fast readout of all the pixels in the image data, and also quickly transfer the digitized image data is generated to the television display system. Low noise, large enough to signal storage capacitor, gain real-time correction and dark current correction, 12-14 bit A / D conversion, to ensure that inherited the large dynamic range characteristics. FPD-DF or quasi real-time system can obtain high-quality images in real-time perspective.

FPD Application of DR and DF have a good start. FPD replacement screen - film and image intensifier system is the trend. Currently, FPD price is also more expensive, in the application there are some limitations such as FPD people still can not do the various parts of the wish-ray fluoroscopy and radiography requirements of the various parts. With further enhance the performance and functionality of FPD prices decline further and applied research further, FPDDR and FPD-DF systems will become indispensable equipment of Radiology. Will better serve the clinical, medical personnel and all mankind.