Difference between medical display and ordinary display

Different from the application fields of ordinary displays, the technical requirements have different parameters. The following comparison shows that a professional medical display must support DICOM PART 14 standard, that is, it must have the ability to adjust the DICOM standard curve to make it conform to DICOM standard, so as to ensure the display quality of images.

General size: the display size is expressed by diagonal length, and the mainstream size of ordinary displays is generally 15 ",17" and 19 "inches;

The common sizes of medical displays are 18 ",20" and 2 1 ",which are basically similar to X-rays.

Support gray scale display: gray scale is a very important feature of black-and-white medical images, reflecting the hierarchical relationship between black-and-white images.

Gray display needs graphics card support, and medical special display needs special graphics card;

Ordinary displays include: 8bit- 256 gray scale, used to display color images, no gray scale requirements, using ordinary graphics cards;

Medical displays include: 10 bit- 1024 gray scale, which is used to display X-ray gray scale images and is related to diagnosis. Requirements: 10 bit1/kloc-0 bit (1024 * 2048 gray scale). Support BBS function (stable brightness control)

The brightness of the display will decay with time. Due to the lack of stable brightness control and calibration, ordinary displays not only decay quickly, but also cannot keep their brightness at a level suitable for the naked eye for a long time due to the influence of the environment. Considering this problem, professional medical gray-scale display adopts stable brightness control technology to calibrate the brightness feedback information of the display at any time to keep it above the standard brightness and meet the clinical reading standards. Brightness means that the image displayed on the monitor has how bright. The brighter the display, the larger the dynamic range that can be generated in the image, so that people can distinguish more tones in the image. This dynamic range must provide a complete 8-8 bit grayscale image (i.e. 256 different tones).

Ordinary displays have the following requirements: 200-300cd/m2 without constant brightness; The medical display includes: 600-700 cd/m2, and the brightness after correction setting is between 400-500 cd/m2; It is required that the brightness value of 30,000 hours or even 65,438+million hours remain unchanged.

Constant brightness is very important for medical display to ensure that the brightness of the display does not change with time. The experimental research shows that the relationship between the brightness of the display and the sensitivity of the naked eye is 700 when the brightness is 500 cd/m2, 777 (maximum) when the brightness is 800 cd/m2, and the ideal brightness is 400~500 cd/m2, and the brightness ≥700 cd/m2 can be selected. The number of pixels actually displayed per unit area, such as 800*600, 1200* 1600, etc.

Ordinary monitors are: 1024*768,1280 *1204; Basically, it is a horizontal screen display, and there is no need for horizontal/vertical screen conversion; Medical display includes: according to the needs of images, horizontal/vertical screen conversion,

1024* 1280 (vertical screen)/1280* 1024 (vertical screen),

It is called1100,000 pixels (1MP), which is commonly used in horizontal display and is mostly suitable for CT, MRI and digital gastrointestinal machines.

1200* 1600 (portrait screen)/1600* 1200 (landscape screen);

Known as 2MP (1K for short), it is often used for vertical screen display, and is mostly suitable for CR, DSA, digital gastrointestinal machine and PACS film reading workstation.

1536*2048 (portrait screen) /2048* 1536 (landscape screen); It is called 3 million pixels (3MP), or 1.5 K for short. Commonly used for vertical screen display, mostly suitable for CCD-DR and PACS diagnostic workstations.

2048*2560 (vertical screen) /2560*2048 (horizontal screen);

Commonly known as 5 million pixels (5MP), referred to as 2 K, it is often used for vertical screen display, and is mostly suitable for flat-panel DR, breast machine and PACS diagnostic workstation;

The resolution of medical display is directly proportional to the price and the resolution of radiation equipment, and the corresponding equipment should be equipped with a display with corresponding resolution. Response time

Response time refers to the response speed of the sea liquid crystal display to the input signal, that is, the response time of the liquid crystal from dark to bright or from bright to dark. Usually calculated in milliseconds (ms). Generally speaking, the response time is divided into two parts-rise time and fall time, and the response time we are talking about is the sum of the two. There is a phenomenon of "visual residue" in the human eye, that is, moving pictures will form a short impression in the human brain, and the acceptable picture display speed is generally 24 frames per second, which is also the origin of the movie playback speed of 24 frames per second. If the display speed is lower than this standard, people will obviously feel the pause and discomfort of the picture. According to this standard, the display time of each picture needs to be less than 40ms, but according to the actual use of LCD, the response time is 30ms( 1/0.03=33.3 frames/second), and there will still be tailing phenomenon, which is not suitable for real-time playback of dynamic medical images. The response time below 25ms (1/0.025=40 frames per second) can meet the real-time playback of clinical cardiovascular DSA.

In the choice of medical display, CR and DR still images do not require high response time. However, in the system configuration of playing dynamic images, such as cardiovascular machines and digital gastrointestinal machines, medical monitors with response time below 25ms should be preferred. Ordinary monitors include: environmental protection and electromagnetic related certifications, such as:

Medical monitors have: not only environmental protection and electromagnetic related certification, but also medical industry certification, in order to enter the medical field and get legal recognition.

EU UL certification, China CCC certification. Ordinary monitors include: protection board without LCD screen, built-in power supply and no special requirements.

Medical monitors include: due to the requirements of teaching and the habits of doctors, liquid crystal protection panels and medical special power supplies are specially equipped for the medical environment. Contrast is also called dynamic range. Contrast describes the difference between black and white, and expresses the ratio of the brightest value to the darkest value of the display. There are not many requirements for color display, but medical displays are required to show the degree between black and white of gray images.

Ordinary display is: 300:1~ 400:1;

The medical indication is: 600:1~1000:1;

The contrast ratio of medical display is as high as 1000: 1, which requires great contrast to display all colors. Generally, it is better to choose contrast ≥600. The accuracy of the graphics card directly affects the quality of the output image, and it is ideal to choose a graphics card with high bit if conditions permit.

Ordinary displays include: memory, speed, 3D indicator light and common AGP slot;

Medical display includes: common PCI slot, display mode, one card dual display, main and auxiliary display interchange, color-black and white conversion, 10bit, 12bit gray output; Horizontal/vertical screen conversion;

⑴ Display mode: When the diagnostic workstation needs two or more monitors, the display card should have flexible display mode to facilitate the doctor's diagnosis. Medical special gray-scale series graphics cards, the display modes are: independent display, extended display, copy display.

⑵ One card with dual display: When a workstation is equipped with two monitors, the graphics card has two output ports.

(3) Interchange of main and auxiliary monitors: when the workstation has a common monitor and one or more medical monitors at the same time; When the ordinary display is set as the main display and the medical display is set as the auxiliary display, when the ordinary display and the medical display respectively display color and grayscale images, there should be no color shortage in color and no fault in grayscale, but it is difficult for the medical graphics card to have the best of both worlds. Often, when the ordinary display is the main display, the medical display will appear gray-scale fault phenomenon; When the medical display is the main display, the color display will lack color, but when the program menu is opened, words always appear on the high-resolution medical display, which is very small and monochrome, which is very inconvenient to use. This is a common technical problem of medical graphics cards. Gray series medical graphics cards completely solve the problems of color fading and gray discontinuity when the main and auxiliary monitors are set. No matter whether it is a medical display or a common display as the main display, there will be no problems of color and gray scale, which has solved PACS companies and hospitals.

⑷ Color-black-and-white conversion: medical graphics card (gray-scale graphics card) with medical display. When displaying color images, RGB signals of three primary colors often only use G color to represent gray images, so when color images are displayed as gray images, the information of two primary colors, R and B, is lost.

Medical special gray-scale series graphics cards, through technical processing, display RGB signals completely on the gray-scale display without losing any color information.

5]10 bit grayscale output: Ordinary graphics card technology is based on WINDOWS technology platform, so it is an 8-bit output signal, and the grayscale should be 256 grayscale. Because the color palette of WINDOWS system monopolizes 20 gray levels, the gray levels actually displayed by the monitor become 236 gray levels, and some images will have obvious gray level faults, which is also the reason why ordinary graphics cards cannot replace medical graphics cards.

The output problems of 10bit and 1 1bit are considered for medical special graphics cards. However, some accompanying development packages need to be redeveloped by PACS company, which is not suitable for China.

Medical special series graphics cards 3MP and 5MP adopt 10bit technology, and the display gray scale is 1024, which is convenient to use and has good compatibility.

[6] Horizontal screen/vertical screen conversion;

Ordinary graphics card: with horizontal display, such as 1024*768, 1280* 1024.

Medical special graphics card: with horizontal/vertical display settings. Generally, CT, MRI, DSA and molybdenum targets are used for horizontal display, while CR and DR chest films are used for vertical display.

That is,1MP:1024 *1280 (vertical screen)//kloc-0 *1024 (horizontal screen) is called1million pixels, which is often used for horizontal screen display.

2MP: 1200 * 1600 (vertical screen)/1600* 1200 (horizontal screen) is called 2 million pixels, abbreviated PACS 1K, which is often used for vertical screen display, especially for CR and Cr.

3mp: 1536 * 2048 (vertical screen) /2048* 1536 (horizontal screen) is called 3 million pixels, abbreviated as 1.5K, which is often used for vertical screen display and is mostly suitable for CCD-DR and PACS diagnostic workstations.

5mp: 2048 * 2560 (vertical screen) /2560*2048 (horizontal screen) is called 5 million pixels, which is often used for vertical screen display, and is mostly suitable for flat-panel DR, breast machine and PACS diagnostic workstations.

Medical monitors are all gray-scale, but the graphics cards on the market are generally color, which can not accurately express the difference of gray-scale. Medical monitors are extremely expensive, so it is very necessary to conduct performance tests regularly, which is called calibration.

Compared with common monitors, medical monitors are expensive and require high calibration. There are two main calibration methods for medical displays: external and internal, and the internal is divided into front and back.

Monitor calibration, strictly speaking, should be through the "display link" to calibrate the "display effect" of the monitor. Its purpose is to maintain the standardization and consistency of digital image display.

The calibration object is mainly the brightness value of each pixel on the display (usually ftL is lumens per foot), followed by spatial distortion (such as drawing a straight line to represent a curve and a square to represent a rectangle or trapezoid). Medical display is different from ordinary display, which focuses on the calibration of brightness value.

Brightness value mainly calibrates three values: maximum brightness value, minimum brightness value and linearity.

To meet the above requirements in terms of parameters and performance, the production capacity is probably less than one millionth of that of ordinary monitors. Can the price of medical monitors be cheap? At present, the purchase and configuration of medical monitors have become the focus of hospitals and PACS integrators. Understanding the differences in technical performance and quality between medical monitors and ordinary monitors, and matching different types and grades of monitors according to the specific situation of our unit can save hospital funds and reflect rationality and economy on the premise of meeting the image quality.

There are also some medical monitors whose parameters are different from those of ordinary monitors, so I won't repeat them here.