Abstract
Ultra-widefield fluorescein angiography (UWFA) is an emerging imaging modality used to characterise pathologies in the retinal vasculature, such as microaneurysms (MAs) and vascular leakages. Despite its potential value for diagnosis and disease screening, objective quantitative assessment of retinal pathologies by UWFA is currently limited because laborious manual processing is required. In this report, we describe a geometrical method for uneven brightness compensation inherent to UWFA imaging technique. The correction function is based on the geometrical eyeball shape, therefore it is fully automated and depends only on pixel distance from the center of the imaged retina. The method’s performance was assessed on a database containing 256 UWFA images with the use of several image quality measures that show the correction method improves image quality. The method is also compared to the commonly used CLAHE approach and was also employed in a pilot study for vascular segmentation, giving a noticeable improvement in segmentation results. Therefore, the method can be used as an image preprocessing step in retinal UWFA image analysis.
Highlights
Fluorescein angiography was introduced as a diagnostic tool over 50 years ago
The results are presented using boxplots grouped in the four categories of image quality measures
The proposed Ultra-wide field fluorescein angiography (UWFA) image preprocessing was applied during a pilot study The proposed image preprocessing applied consisted during a pilot study dedicated to retinalUWFA
Summary
Fluorescein angiography was introduced as a diagnostic tool over 50 years ago. The literature says that first pathological changes occur in the peripheral area of the retina and, as the disease progresses, cover an area increasingly larger towards the center. In recent years three approaches have been introduced to expand the visible retina area: (1) assembly of traditional angiograms, i.e., several images and at least two acquisition protocols; (2) adding an additional lens to the optical path of the classic camera; (3) introduction of new devices enabling observation of a wider area of the retina [3,4]. Ultra-wide field fluorescein angiography (UWFA) is an extension of the third group of methods and enables imaging of a significantly larger retinal area (with angle over 200◦ ) [1]. Comparing the UWFA with a classic fundus camera, the obtained 200◦ from the center of the eye corresponds to a conventional angle measure of approximately 125◦ [2]
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