Some differences between medical liquid crystal display and ordinary display

Medical display is a high-definition and high-brightness high-end display device in the display field.

With the maturity and popularization of PACS technology and the rapid development of various digital imaging devices, medical display is a terminal image presenter for doctors to observe and diagnose patients through "soft reading", which is different from ordinary display for displaying black-and-white and color images or characters.

Taking LCD as an example, this paper compares the technical parameters, functions and safety certification.

1, technical parameters

① Size: Calculated by diagonal length, generally in inches.

Medical use: basically similar to X-ray film, the common sizes are: 18 ",20", 2 1 ".

Ordinary: Common sizes are: 19 ",22", 24 "and 27";

② Resolution: The number of pixels actually displayed per unit area. 1mp = 1mp

Medical use:1MP (1024×1280) 2mp (1200×1600) 3mp (1536× 2048) 5mp (.

Ordinary: 800×600, 1024×768, 1280× 1204.

③ Brightness: Brightness is the brightness of the image displayed on the monitor, and the unit is cd/m2 candela per square meter.

Medical use: the brightness set by the standard calibration of 600-700 cd/m2 is between 400-500 cd/m2; It is required to keep the brightness value unchanged for 30,000 hours or even 654.38+100,000 hours.

Ordinary: 200-300 cd/m2 without special requirements.

④ Contrast: Describe the difference between black and white displayed by the display and express the ratio of the brightest value to the darkest value of the display. Contrast is also called dynamic range.

Medical treatment: 600:1-1000:1general: 300: 1-400: 1

⑤ Gray scale: It reflects the hierarchical relationship between black and white images and is a very important feature of black and white medical images. Gray display requires a dedicated graphics card.

Medicine: 10bit- 1024 gray scale, 10bit or 12 bit (1024-2048 gray scale).

Normal: 6-bit -64, 8-bit-256 grayscale

⑥ visual angle

Medical treatment: up and down/left and right can reach 178.

Ordinary: Up and down viewing angles are about 140, and left and right viewing angles are about 160.

⑦ Response time: refers to the response speed of LCD to input signals, that is, the response time of LCD from dark to bright or from bright to dark. It is usually calculated in milliseconds (ms)

Medicine: For some dynamic high-definition images, it is usually about a few milliseconds, and the requirements for static images are not high.

Ordinary: about 16-5 ms

2. Function

① dicom PART 14 standard: dicom curve is one of the most important parameters in the display characteristics, which directly reflects the performance of the display.

Due to the characteristics of electronic components, the input and output of the display are not ideal linear relations. At both ends of the input-output characteristic curve, the change of output caused by the change of input is not obvious enough. Assuming that the input-output range is 0-99, in the initial stage, the input is 3, and perhaps its output is only 1. If this situation is directly applied to medical images, it will be found that the display cannot correctly identify some subtle density changes of soft tissues (as shown in Figure 2). In order to specify a specification for the performance of medical displays, the World Medical Organization has formulated the dicom standard, which is to widen the difference of each gray level, that is, when the input is 3, the output is also 3.

Medical treatment: it has the ability to adjust DICOM standard curve to make it conform to DICOM standard, thus ensuring the display quality of images.

Normal: None

② SBC function: constant brightness level function.

The brightness of the display will decrease with the use time (as shown in Figure 3). In order to meet the standard of clinical film reading, the stability, consistency and integrity of an image (referring to the same image displayed on workstations in different parts of the hospital with the same brightness, gray scale and contrast, so that doctors in different places can see the same image; The printed image is the same as the image displayed on the monitor), and the brightness needs to be monitored, calibrated, adjusted and controlled at any time to keep it between 400-500 CD/m2 standards and keep the brightness value not less than 30,000 hours.

Medical: There is an optical sensor interface on the back, which can be connected with an optical sensor for calibration to ensure the consistency and integrity of the system display.

Normal: There is no kinetic energy for brightness monitoring, and the brightness decays fast enough.

③ Display mode: When a diagnostic workstation needs two or more monitors, and so on.

Medical treatment: horizontal/vertical screen conversion, 10 bit- 12 bit grayscale output; Combined with the functions of the graphics card, the functions of independent display, extended display, copy display, color-black and white conversion, exchange of main and auxiliary display, and dual display of one card are completed.

Normal: Normal mode

3. Certificate

① Medical certificate

Medical use: FDA5 10(k), ISO 13485.

Normal: None

② Safety certification

Medicine: CE, UL, CCC

Commonly used: CCC and other basic standards.

In addition, due to the requirements of teaching and the habits of doctors, doctors at home and abroad are used to pointing at the film or display screen with pens to express their views on the specific details of the image. Liquid crystal materials are easily damaged. In order to adapt to the medical environment, display manufacturers will responsibly install LCD protection plates in the production process.