The Method Of Extracting Hypertension Lesions From The Image Based On Non-Fluorescence Fundus Angiography

The development of image processing technology has been widely applied to the scientific research, industrial and agricultural production, military technology, government departments, medical hygiene and many other fields, further promoting the development of social productivity. Today, the multidisciplinary cross-integration of digital image processing make science and technology gradually infiltrate into other areas and it is inevitable to be applied by many other subjects. Both in theory and in practice, digital image processing has the great potential in information society. Medical image processing and analysis are always the focus and difficult problems for the research of image processing and analysis. By dint of the means of graph and image technology, the displaying method and quality of medical image got a tremendous improvement, which has been greatly improved the level of diagnosis. Optic fundus has been the focus of clinical medicine because retinal lesions are closely related to the diseases of other system of the whole body. Therefore, the special signs of optic fundus can be helpful to make a correct diagnosis and prognosis estimates.The optic fundus is "barometer" which reflect the changes of hypertensive condition. According to observing the condition of retinal arterial vessel, such as the changes of blood vessel diameter and vascular wall, the phenomenon of cross and oppression, retinal hemorrhage, exudates and its property etc., people can acquaint the whole body vascular condition Fluorescence fundus angiography is commonly used on ophthalmic clinical examination, especially for pathologic diagnosis of optic fundus and the choice of treatment. However, some side effects were reported in theapplication of this technology. Fluorescence sodium which is used as the contrast agent will result in vary effects such as nausea, vomiting, numbness or shock, cardiac arrest and other adverse reactions. Therefore, it is significant to research the means of non-Fluorescence fundus angiography. Taking account of the accuracy, objectivity, reproducibility and universality of the results of optic fundus examination, it is vital to improve the analysis of fundus images especially the quantitative analysis for retinal vessels and the extraction of retinal exudates which is closely related to hypertension. Consequently, it is essential to take effective method to segregate optic fundus images and automatically analyze and measure vascular width. Based on the changes of retinal vascular pattern, this helps ophthalmologist to make early diagnosis, monitor treatment and estimate postoperative recovery with the great clinical significance.In this paper, base on the analysis of the characteristics of the fundus image, a lot of experiments were finished with the Visual C + + system and extract two kinds of hypertension lesions were extracted from the non-fluorescence fundus angiography images.(1) The measurements of the blood vessel diameter in the fundus images. The optic fundus images of the hypertensive sufferer are often very unclear because of complex blood vessels, retinal hemorrhage, exudates and such lesions represent. More noise also is interferential for the follow-up identification. Therefore, the fundus images must be pretreated to reduce unrelated information for the validity, veracity of exacting eigen value. In this paper, gray linear transform in green gray image was taken to enhance the definition in the retinal RGB image, Sobel operator was applied to detect images edge and the binary image processing was performed by the settledthreshold segmentation. But there are still a lot of noise points. Subsequently, noise was reduced to process the follow-up image. After that, image quality has been improved; image features has been enhanced; Noise has been reduced, the result of image processing and analyzing has been improved and operating speed has been accelerated. As the matching pattern of retinal vascular identified system, detecting the location of the retinal optic disc is the key to identification of the retinal vessels in the optic fundus images. The border of retinal optic disc has a simple geometric shape--round features. According to the geometric characteristics of the optic disc, the Hough transform was used to detect the optic disc and it is also helpful for the next step of the measurement of vascular diameter. To reduce the amount of computation, a rectangular region was designated as the working area according to the vascular distribution in the vicinity of the optic disc. In this paper, two methods of retinal vascular diameter were applied. The first method adopted by the least square method of vascular wall for curve fitting, choose center of the optic disc which the Hough transform detect as the center to draw a circle which intersect with the vascular wall. With this way, nodal striking distance is the vessel diameter. The second method adopted the closing operation of mathematical morphology for de-noising retinal images, to fill vein first without changes in the diameter of the artery and then to measure the diameter. According to the ratio of the average artery and vein diameter, the retinal image can be judged whether it is of Hypertension retinal images. By contrast, the first method is more applicable to the detection of poor continuity of the vascular wall; the second method is adaptive for anti-jamming.(2) The lesions extraction of retinal exudates. Since the gray values of yellow retinal exudates and the color of the optic disc are very similar, according to the geometric characteristics of optic disc, it is necessary to apply the Hough transform first to positioning the optic disc, and then fill it. Adopting the image segmentation algorithm, the yellow retinal exudates can be extracted on the exact location in retinal images of the gray level.With the extensive data collection, as well as the analysis and summary of existing medical retinal image processing, extract methods from hypertension lesions in non-fluorescence fundus angiography images was proposed in this paper, which can measure the diameter of the retinal vessels. According the ratio of its diameter, early diagnosis for hypertension can be finished. Meanwhile, with the accurate extraction of retinal exudates of hypertension and the clear identification between the normal and the abnormal, the standardization of hypertension research of non-fluorescence fundus angiography images can be enhanced, thus greatly strengthening the advantage of retinal examination with convenience for patients. It is also clinically significant for the diagnosis and treatment of hypertensive patients.