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In the field of medical imaging, human upper gastrointestinal (GI) endoscopy plays a crucial role in diagnosing and managing various pathologies. However, the diagnostic efficacy of this minimally invasive procedure is often hindered by suboptimal imaging conditions, such as inadequate and irregular illumination, leading to blurred visual details. These challenges underscore the necessity for advanced image enhancement techniques that can effectively address such issues and consequently enhance clinical decision-making. This study aims to propose an innovative algorithm for enhancing image contrast and brightness specifically designed for upper GI endoscopy. Recognizing the shortcomings of current methods in dealing with complex endoscopic images, our research focuses on developing a solution that addresses the dual problems of insufficient and uneven illumination. Our goal is to enhance the visibility of critical anatomical structures without introducing artifacts. Our method innovatively integrates adaptive gamma correction for luminance enhancement with a contrast-limited adaptive histogram equalization (CLAHE) algorithm. Applying these techniques separately to the input images and then performing a weighted fusion, our approach achieves a balanced optimization of image contrast and brightness. This fusion strategy ensures that important image details are preserved while mitigating potential issues such as over-enhancement and noise enhancement that may be associated with individual algorithms. To rigorously evaluate the performance of our proposed algorithm, a series of experiments were conducted on a subset of upper gastrointestinal (GI) images from an open-access dataset. The evaluation included comparisons with several established enhancement algorithms using quantitative metrics such as peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and natural image quality evaluator (NIQE). The empirical results showed that our algorithm consistently outperformed existing methods on these metrics, demonstrating its superior ability to enhance image quality. Specifically, it achieved higher PSNR values, indicating reduced noise and distortion, and improved SSIM values, reflecting better structural preservation similar to the original image. Furthermore, the decreased NIQE scores validated the naturalness and perceptual quality of the enhanced images. In conclusion, this research introduces a novel and effective image enhancement algorithm for upper GI endoscopy that effectively tackles the common issue of insufficient and inconsistent illumination. The proven ability of this technology to enhance image quality without compromising diagnostic integrity paves the way for more accurate and efficient endoscopic examinations, reinforcing its importance as a cornerstone in the advancement of gastrointestinal diagnostic imaging.
Flowchart of the multilayer fusion algorithm
(a) Origin; (b) Layer1 luminance enhancement algorithm; (c) Layer 2 CLAHE algorithm; (d) Layer 3 linear fusion algorithm
Comparison of different algorithms for three sets of images (a-c) of Pylorus
Comparison of different algorithms for three sets of images (a-c) of Retroflex-stomach
Comparison of different algorithms for three sets of images (a-c) of Z-line