The Development Of Narrow Band Imaging Endoscopic Video System Based On LED Light Source

Esophagus, stomach, colon and colorectal cancer which belong to gastrointestinal disease have high incidence in our country, In recent years, with the further promotion of the endoscopic techniques, the diagnostic rate of gastrointestinal diseases continues increasing, but the find and diagnostic rate of early lesions still need to be further improved.Studies showed that tumor’s formation are all along with angiogenesis. The angiogenesis make mucosa vascular color and texture morphological different between early cancer and its surrounding tissues. Besides, this phenomenon is considered to have direct relationship with the occurrence and progression of dysplasia or cancer. The early lesions of gastrointestinal cancer are often expressed as a flat type and depressed small mucosal lesions, which often appears abnormal micro vascular morphological changes. But the ordinary white light source endoscopic system is difficult to see this kind vascular change. If there are equipment to make the micro vessels’ morphological can be highlighted, the diagnostic rate of early lesions will be improved greatly.Based on above clinical background, through the experts’ continuous efforts, there have appeared many new electronic endoscopic techniques who can help doctor observe vessels’ morphological submucosal. They included Olympus Narrow Band Imaging technology (NBI), Fujinon Intelligent Electronic Spectroscopic Colorimetric Technique (FICE) and PENTAX’s I-Scan technology. This article referred to the above three systems for special optical endoscopy system.There is one narrowband rotary filter who joints with Olympus narrowband imaging system’s hernia white light source. The narrowband rotary filter’s dominant wavelength is 415nm and 540nm, its bandwidth is 30nm.This white light source across the narrowband rotary filter to generate narrowband light, the narrowband light across electronic endoscope via optical fiber arrival to the examinational position. CCD image Sensor that locates electronic endoscope tip senses the optical signal reflected by the examinational position,then convert the optical signal into electrical signal, then transfer the electrical signal to the image processing workstation for narrowband image processing. FICE system uses the system back-end software process the white image what the system has acquired. This system software isolate the white light image to monochrome image as every5nm wavelength spectroscopic image intervals, the doctor can reconstruct spectroscopic image according to his inspection need. I-SCAN system, the system’s front end software control the white light source and make it emits narrowband spectrum, the rear end process the digital image signal output from the image Sensor to generate narrowband image.Three techniques above are all based on narrow band illuminate and optical image enhancement technology. These inventions are in order to improve the contrast within the mucosal tissue and blood vessels’surrounding tissue, they can enhanced the vascular morphology mucosal display, Allows doctors to distinguish early cancer and improve early cancer detection rate.Above systems, all use the hernia white cold light source as the base luminous lighting source. The hernia white cold light source as high short life time, need to be replaced once every 500h, high cost. They are designed with separated components, the structure complex, millions of expensive price against a wide range of its widespread use, because disease early detection technology cannot be spread.This paper conducting research for solving above problems, it developed one narrowband imaging endoscopic imaging system based on LED light source, herein referred to it as LED-NBI system. The system has simple produce principle of narrow- band light, compact structure, high reliability, high system integration, it can be used as a handheld portable devices. Manufacturing cost is greatly reduced at the same time, and it has advantages to be popularized to grassroots medical institutions or medical market. As one kind of submucosal lesions early screening equipment, it greatly improve as a whole early cancer detection rate in society, reduce the medical cost.The system uses IMX6 processor as the main control subsystem’s core, its mainly responsible for:control the ratio of narrow-band light and luminous flux; the image signal processor ISP output digital video signal decoding process; process the video frame by frame according to the NBI imaging signal processing; control of streaming video multiplex display and storage. IMX6 processor is the core of this system, IMX6 processor and image signal processor ISP constitute the software and hardware processing platform of the systemNarrow band light source subsystem is composed of narrow-band LED light source, circuit and the corresponding control program. The main material suction light of intravascular hemoglobin is the wavelength of 415 nm blue ribbon light and the wavelength of 540 nm green light. Penetration of light depend optical wavelength, the longer the wavelength of light, the stronger penetration of the organization.415 nm blue narrow-band light’s penetration ability is weak, only can exposure to tissue mucous membrane surface. Under the irradiation of 415 nm blue narrow-band light, the micro vascular structure of mucosal surface can be good shown. And 540 nm green narrowband light can illuminate the lower organization of mucous membrane, under the irradiation of it, the system can display mucosal micro vascular structure of the middle organization well. Early cancer usually occurs in the mucosal surface and middle, so this paper takes the center wavelength of 415 nm narrowband blue light and the wavelength of 540 nm green narrow-band light source as light source Through the selection and test repeatedly, finally this paper determined to use the half high width of 18 nm, wavelength of 415 nm blue ribbon LED and a half high width of 20 nm wavelength for 540 nm green narrowband LED as system’s main light source. And this paper customized small batch samples. In order to make sure the spectral energy the two kinds of narrow-band light irradiated uniform distribution, this paper, according to test data, made blue LED light and green light narrowband LED light source as the proportion of 2:1, parallel packaging in one optical lens.Because of the different environment need different light intensity of illumination, besides, light emission spectral characteristics will change as the current size vary. Aim at above problem, this paper designed one current control circuit and the corresponding program to adjust the current size of the light source. User can adjust the light source current size through rotate the knob.Image acquisition and processing subsystem include CMOS Image Sensor (CMOS Image Sensor, SENSOR), and Image Signal Processor (Image Signal Processor, ISP).This paper used backside illuminate Sensor. It has good low illumination characteristics. It can effectively increase image contrast, reduce noises. ISP integrated with more basic image processing algorithms, including automatic exposure, automatic white balance, gamma correction and dynamic range adjustment. This system is based on the imaging principles of NBI, with the aid of the ISP, RGB channel information of the original to be matched, the 415 nm light produced by the B channel signal assigned to B and G channel at the same time, make the superficial capillaries in tan, will have a G 540 nm light channel signal assigned to R make deep bulky blood vessels of the blue, it effectively highlight the vascular structures in areas of mucosal tissue. ISP can real-time adjust the exposure time of SENSOR and gain, and the SENSOR acquisition according environment.ISP processed the signals come from SENSOR effectively. ISP communicate with IMX6 processor bus at high speed, ISP transferred the processed video information to IMX6 processor for the video signal processor decoding process and output display.This paper uses 4 inch’s TFT LCD screen and HDMI external professional medical HD displayer for image showing, they all support up to 1920* 1080,60 frames video signal communication. This professional medical support HD of followed image format:sRGB, Adobe RGB, DICOM, PROGRAMMABLE, it is free to choose any format of the above five kinds to observe video and image. In addition, the professional medical display support 10 bit band wide color gamut,14 bit gamma correction function,1000:1107.34 million kinds high contrast of color display. Because of its above characteristics, this displayer can vividly show the major parts detail, to improve the doctor’s objective diagnostic rate.Relative to Olympus NBI system, FICE system and I-SCAN system, the LED-NBI system has a simple lighting, high integration of image acquisition and image processing system and powerful main processor. Olympus NBI system, FICE and I-SCAN system adopts component separated design, large system structure, not convenient to move easily. However LED-NBI system make light source,image Sensor image acquisition system and the main processor integration on one handheld device, it can be applicable to the outpatient service, emergency endoscopy room and so on.This paper designed one LED-NBI system.It can be comparable with the Olympus NBI system in imaging quality aspect. In using process, the doctor can adjust the system’s the light source current size according to the need of clinical. It can effectively highlight the vascular morphology of mucous membrane, increase blood vessels and the surrounding tissue contrast, increase cancer detection and it has important clinical significance.To sum up, the system has many other advantages such as good performance, small size, simple structure, low cost, portable use, widely applicability.