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Medical imaging systems in the digital display and optional role
2011-11-06 by seoer1

Digital imaging system (PACS, DR, CR, DSA, etc.) As the IT industry, maturing soon into the field of medical radiology. Because of its "soft feature film read," and forward-looking, more and more favored by domestic hospitals, a variety of medical digital imaging systems have been classified into the hospital's purchasing program. However, due to cost considerations, the digital image display system configuration, it is often ignored or discarded medical display configuration, or an ordinary PC monitor displays black and white alternative, the digital imaging system, image display greatly reduced, as China's current development of a digital image "bottleneck."

At present, many domestic manufacturers, integrators in the digital X-machine, CR, DR systems and PACS systems investment allocation ratio, the display of matching parameters and the investment ratio is low, the natural display relatively low, leading to our current digital imaging overall function of the system a "bucket effect", that is the lowest parts of the overall system function = function, this phenomenon is due to the domestic industry's lack of understanding of medical monitors caused. For scholars of radiology diagnostic accuracy of digital imaging systems have a full understanding of the problem, understand the medical monitor's role in the digital image, we discuss several aspects of medical monitors.

Medical monitor parameters:

1, the brightness of the gray scale of the human eye with the ability to distinguish the different brightness, has a nonlinear relationship. As shown, the brightness (Luminance) the higher the human eye can distinguish the gray scale (JND-Just Noticeable Difference) more. Conversely, low brightness, grayscale resolution on the human eye is poor. The higher the brightness, the human eye can distinguish between the gray scale on the more. In order to improve the gray scale resolution, the display will require high brightness. Brightness (Luminance) the higher the human eye can distinguish between the gray (JND - Just Noticeable Difference) is also more. Doctors reading room of the brightness of ambient light on the display is influential, bright display image depends in part on the brightness of the display, but the dark part of the addition to the display brightness, ambient light and screen with the refractive index.

If the indoor illumination 100lux, display refraction of 2%, the brightness of 2 cd/M2. When asked to contrast ratio of 1:100, the display brightness should be at least 200 cd/M2 (general office of the illumination can often reach 500lux, requires the display's brightness can reach 1000 cd/M2) such as non-linear gray eye ability to identify and rank environmental illumination factors.

Design and manufacture of medical displays the maximum brightness of 800-600 cd/M2. Ordinary display brightness 200-350 cd/M2. American College of Radiology (ACR) provides digital X-ray images of the maximum brightness should be at least 170 cd/M2. 2001, in March to discuss the German X-ray imaging at the industry view is that all digital images with the brightness of the monitor requires at least to 200 cd/M2. General perspective or CT images of at least 100 cd/M2. So From this, the general brightness of the display seems to have reached the brightness of film-reading requirements (many hospitals have just installed the display image is also quite satisfactory). Taking into account the CRT or LCD display panels, the brightness will decay over time.

We hope that at least three years time, the display's brightness can be maintained at minimum brightness above, it is proposed that the new display's brightness should be at least 500 cd/M2 more. However, due to the normal display brightness stability and no correction, brightness decay over time and environmental light refraction, display brightness greatly discount, can not really film-reading requirements (on the brightness issue, even within the stability in detail later) The medical monitor's brightness in the installation place, the use of optical correction means for correction according to DICOM standard, so that the brightness in a film-reading required to maintain the brightness value. (Generally between 400-500 cd/M2), and to ensure constant at 3-5 ten thousand hours. This ensures that the brightness of the image of stability and consistency. From this, general medical monitors and medical monitors in radiology reading room of the actual function of the work environment is very different.

2, gray on gray-scale response to the human eye is not a linear relationship. Our eyes to the bright and dark parts as part of the response sensitivity. DICOM 3.0 Chapter XIV to display grayscale images provide a standard display function (Figure 5). Use the standard display function in a different light to display images on the display system can provide some degree of similarity. After this function into the gray scale, the human eye's response is nearly linear relationship. Therefore, a good medical monitor, it is necessary to adjust the gray scale curve has to comply with the provisions of the gray scale DICOM3.14 function in the function. The higher brightness of the display system is able to show more number of distinguishable gray (JND).

In the diagnostic radiology, this gray-scale differences (differences in tissue density), it is possible for early diagnosis of lesions of great help. Display images in black and white grayscale display and graphics related to the number is, more concerned with ordinary graphics color display parameters, such as: memory, speed, color bits, etc. However, windows system is 8bit output display to reflect the black and white images grayscale, or 256 gray because of the windows in an exclusive palette to 20 colors, the image is actually only 236 shades of gray, which is often encountered in ordinary gray scale graphics are not a continuous problem. To achieve a perfect reproduction of gray scale continuous black and white images, it should be optional professional grayscale output than in 10bit graphics.

Medical monitor stability, integrity and consistency:

1 stability relative to the normal display, medical grayscale display the price is more expensive, and we hope that life can be more than 5 years. Whether CRT or LC7981 Graphic LCD module, the brightness will decay over time. Life is defined as the general display When the light attenuation to the maximum brightness of 50% of the time for liquid crystal displays, this time about 30,000 hours to 50,000 hours life time, even in the brightness is not the same every day, so from time to time (about three months to six months), brightness and grayscale display must do the correction, in order to ensure consistency in the display if the display lot number, the workload is considerable. the more advanced display internal sensor (Sensor), can detect changes in the brightness of the display is automatically adjusted so that the display at any time in life to be able to maintain the brightness and stability. LCD brightness is not very stable and it's brightness will vary with temperature changes and now displays some internal sensors (Sensor), can detect changes in the brightness of the display is automatically adjusted so that you can save a lot of manpower.

Also in the just-machine LCD brightness setting does not immediately reach the brightness. After about 20 - 30 minutes until the brightness reaches the set in below the set brightness Peugeot this time, the display is not suitable for diagnosis with. Users often due to other commitments to stop using the monitor, for some time, start the screen saver starts. Monitor is turned off, which was ordered for the extension of the display is good, but when the user re-started using the monitor display and is just machines state, but have to wait 20-30 minutes to warm machine time. Thus, the use of inconvenient and if off screen saver, but also reduces the service life, so fish and bear's paw, not Jian was. well-designed display, use Built-in sensors to detect when the brightness of the boot and if the brightness below the standard, then improve the power supply voltage, so that the display in 30 seconds to reach the default brightness. In this way, neither waiting for warm-up time, but also in the idle machine start the screen saver to extend monitor life.

2 is the consistency and integrity of consistency: If separated for some time, it shows the same image quality is still the same, as if watching a film with the same. Integrity refers to the different locations in the hospital the same image displayed on the workstation, its brightness, gamma, contrast, etc. is exactly the same, so that doctors in different locations to see the same image; when the printed image and displayed on the monitor on the image is the same. So no matter what the media are also on the same image. The original film in the use of hospital diagnosis, QA (Quality Assurance Quality Assurance) is on the washing machine. Radiologist checked every day washing washing machine speed, syrup concentration and temperature to ensure the quality of each film to wash out is the same. hospital hospital-wide implementation of the PACS system, QA (Quality Assurance Quality Assurance) is on display. displays the number of minority. how the different brands, different usage and different time purchase displays, to ensure the integrity of the image, maintaining the same brightness, same display function has become an important issue, so the choice of display, in addition to the points mentioned above, the display monitor manufacturers can provide QA (Quality Assurance Quality Assurance) and PM (preventive maintenance & planned maintenance preventive maintenance) tools and monitor whether the function of QA is an important factor to consider.

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