DR:
Digital Radiography, Direct Digital Radiography System.
DR consists of a detector, an image processor, and an image monitor. Transmission through the human body after the X-ray signal is detected to obtain, the direct formation of digital images, digital image data to the computer, displayed on the monitor, can also be post-processing. Now the main DR detector for amorphous silicon detector and amorphous selenium detector, the two detectors to obtain the image of the effect of the small difference. Others are multi-filament orthogonal chamber detector, which is an air detector. There is also a CCD detector. Both amorphous silicon detectors and amorphous selenium detectors are known as flat panel detectors.
1. Directly through the professional monitor to read the film, no need to develop film, greatly saving film costs (except for patients with special needs);
2. DR upgrade can be dispensed with a variety of troubles, such as taking the wrong film, taking the wrong film or the patient's body movement leads to poor picture, the doctor can quickly see the impact of the results, and re-shooting.
3. The display of bone structure, articular cartilage and soft tissue is superior to traditional X-ray imaging, and quantitative analysis of mineral salt content can also be performed; easy to display mediastinal structures such as blood vessels and trachea; the detection rate of nodular lesions is higher than that of traditional X-ray imaging; in the observation of intestinal pneumoperitoneum, pneumoperitoneum, and calcium-containing lesions such as stones is superior to traditional X-ray images; body layer imaging is superior to X-ray tomography; gastrointestinal double-contrast imaging is superior to conventional X-ray imaging in showing gastric cells, microscopic lesions and intestinal mucosal folds.
4. DR imaging process The imaging process of DR is a digital imaging process, in which the X-ray detector converts and digitizes the X-ray energy that passes through the human body, and the entire X-ray imaging process, including X-ray acquisition, conversion, quantification, transmission, processing, and display, is a digital information processing process. Digital photography mode has changed the basis of the formation of image information, the carrier of the X-ray signal is no longer a screen / film system, but by the many types of X-ray detector instead of the X-ray detector, X-ray detector through the different signal acquisition principle, the X-ray intensity distribution on behalf of the human body information, using the digital mode of acquisition, conversion, storage, processing and display.
CR:
Computed X-ray Imaging (CR)
Traditional X-ray imaging is by X-ray photography, the image information recorded on film, in the development of stereotypes processing, the image can only be displayed on the photo. In contrast, computed radiography (CR) records the image information from the X-ray on an image plate (IP), which is read by a reading device, and a computer calculates a digitized image, which is then converted by a digital/analog converter to display a grayscale image on a screen. CR and DR as described in DSA are also digital imaging.
CR imaging principle and equipment
CR imaging goes through the steps of recording, reading, processing and displaying image information. The basic structure is shown in Figure 1-6-1.Recording of image information: Instead of X-ray film, an IP made of barium fluorobromide crystals (BaFX: Eu2+, X=CI. Br. I) containing the trace element europium (Eu2+) is used to accept X-rays transmitted through the human body to sensitize the IP to light and form a latent image, and the X-ray image information is recorded by the IP, which can be reused for up to 20,000-30,000 times.
CR imaging principle and equipment
CR imaging goes through the steps of reading, processing and displaying, and the basic structure of CR is shown in Figure 1-6-1.
Reading of image information: The latent image on the IP is read by a laser scanning system (Figure 1-6-2) and converted into a digital signal. The laser beam scans the entirety of the uniformly moving IP accurately and uniformly. The laser-excited fluorescence on the IP is collected by an automatic tracking light collector, converted into an electrical signal by a photoelectric converter, amplified, and converted into digital image information by an analog/digital converter. After scanning from the IP, a digitized image is obtained.
Processing of image information
The digitized signal of the image is processed by the image processing system, and the characteristics of the image can be changed arbitrarily within a certain range. This is the CR is superior to X-ray photographs, X-ray photographs on the image characteristics can not be changed. The main functions of image processing are: gray scale processing, window processing, digital subtraction angiography processing and X-ray absorption rate subtraction processing.
Gray Scale Processing
Through the adjustment of the image processing system, the digital signal can be converted into a black and white image contrast, which is selected within the range that the human eye can discern to achieve the best visual effect. This facilitates the observation of different tissue structures. For example, the chest can get two images that show the lungs and mediastinum optimally respectively.
Window position processing
Taking a certain digital signal as 0, i.e., the center, so that a certain gray scale range of tissue structures, with its difference in the absorption rate of X-rays, to get the best display, and at the same time can be enhanced for these digital signals. Window level processing improves image contrast and facilitates the display of tissue structures, such as the display of bone trabeculae.
Digital Subtraction Angiography (DSA): Selecting one of the frames in a series of CR images of angiography as the negative (mask) for digital subtraction processing, DSA images can be obtained.
X-ray absorption rate subtraction processing
The use of two different radiographic conditions of photography, select any one of the frame as the negative film subtraction, you can eliminate certain tissues. For example, subtraction of the chest eliminates rib images to facilitate visualization of the lung fields.
Image display and storage: the digital image is converted by a digital/analog converter to display a gray-scale image on the screen visible to the human eye. The image on the screen can be observed and analyzed, but also can be used to multi-frame optical camera ingested on film, with a laser camera can be digitized image signals recorded directly on the film, which can improve the quality of the image. The laser camera is integrated with the automatic film processor, which reduces the number of operating procedures.
CR's digitized image information can also be stored on magnetic tape, disk and CD-ROM for long-term preservation.
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