x？ In x-ray photography, CR? With what? Doctor? What is the difference?

* digital radiography (DR)

* Imaging principle: DR and CR convert analog information into digital information, and the difference between them mainly lies in the different ways of X-ray acquisition and image conversion.

CR is an indirect X-ray conversion technology, which uses IP as X-ray medium. After IP is irradiated by X-rays, the intensity change of X-rays is recorded as a latent image. The intensity of the latent image signal decreases with time. The laser scanner generates red laser or near infrared laser. When the laser beam gradually scans the IP surface, the latent image signal is converted into visible light by the laser (photoluminescence effect). The fluorescence emitted by each point on IP is coupled to the photomultiplier tube through a special optical system. The photomultiplier tube converts optical signals with different intensities at each point into electrical signals, which are amplified and sampled, then sent to an analog-to-digital converter for quantization, and then sent to a computer for imaging.

DR directly converts X-ray photons into digital signals by using flat panel detector or fluorescent CCD camera, which has fewer conversion links and reduces noise. The loss of X-ray photon signal is minimized and the image quality is high. DR has no IP processing link, which reduces mechanical failures, improves efficiency and reduces labor intensity.

Image quality: DR has higher resolution, wider dynamic range and higher signal-to-noise ratio than CR.

Exposure dose: DR is about 2/3 of CR.

Work efficiency: DR is more efficient than CR.

System compatibility: CR is compatible with the original X-ray machine, while DR is incompatible with the original X-ray machine.

Dynamic image: The flat panel detector has been able to output dynamic images for perspective collection, which has expanded its application scope.

As far as its clinical application is concerned, DR can completely replace CR, which is the transition from traditional X-ray equipment to digital X-ray equipment.

CR system mainly uses IP detector, commonly known as IP board, which is the carrier to collect and record image information. The imaging principle of CR is that IP board has a kind of light-excited phosphor, which can absorb and store X-ray energy when X-rays shine on it. Then, the captured energy can be released under the excitation of additional laser energy with appropriate wavelength. The release process requires a special CR reader. The released energy is converted into voltage by photomultiplier tube, and the voltage is amplified and then input into analog-to-digital converter, converted into digital, sampled and quantized, and stored in computer. Finally, after reading the image, the data on the IP board is eliminated by applying strong light irradiation so that it can be reused.

DR generally refers to digital photography based on charge coupled device (CCD) technology, and cesium iodide crystal is commonly used as detector material. After the cesium iodide crystal is irradiated by X-rays, X-ray photons can be directly converted into visible light, and the visible light excites the photodiode under the cesium iodide layer, so that the photodiode generates current, which is then stored in the diode's own capacitance. Then, the electric signal is read out by the reading circuit and quantized into a digital signal. Finally, it is transmitted to the image processor through the communication interface and stored in the computer.

So in practical work, it is probably like this.

CR: First, take a blank IP board, input relevant information on the computer, take photos, read the image with a reader and check it with the computer.

Doctor: Computer input related information, photography and computer viewing.

Obviously, DR is much more convenient. If there are many patients, it is necessary to prepare a certain number of blank IP boards in the department. Otherwise, every time I take a picture of a patient, I have to wipe it off before I can take a picture of the next patient. Secondly, if a patient's image does not meet the diagnostic requirements, then CR can only be found on the computer after I read it with a reader, while DR can be seen directly on the computer after exposure.

For an inappropriate example, CR is like an old-fashioned camera, which needs film and needs to be developed in a photo studio to see the image. DR is like a digital camera now. After pressing the shutter, you can see the captured image on the display screen.