Speckle Noise Reduction in Optical Coherence Tomography Images Using a Combination of Edge-Preserving Filters and Discrete Wavelet Transform

Imaging techniques are repeatedly employed by radiologists to detect internal structural details and body function. Optical coherence tomography (OCT) is a significant non-invasive medical imaging modality used to examine the microstructure of biological tissues. In this study, images from ۵۰۰ patients who visited Noor Clinic in Ardabil for OCT imaging of the retina were collected. Since OCT images suffer from speckle noise, edge-preserving filters were utilized for noise reduction. By subtracting the output of the filtered image from the original image, some of the original image information and noise remained in the output. To restore the remaining information, the output resulting from subtracting the original image from the filtered image was decomposed using the discrete wavelet transform and soft thresholding, and the remaining image information was added to the filtered image. Among the edge-preserving filters, the guided filter demonstrated the best performance with MSE, PSNR, and IQI values of ۷۹.۹۴۹, ۲۸.۴۱, and ۰.۹۸۴, respectively, whereas the proposed method achieved values of ۱۹.۸۲۵, ۳۳.۷۸, and ۰.۹۸۹, respectively. After extracting the image information and restoring it to the output of the edge-preserving filters, significant changes in quantitative noise reduction metrics were observed. Consequently, in this study, by employing guided, bilateral, and db۸ wavelet filters, we achieved better performance in preserving the edges of OCT images compared to edge-preserving filters.

کلیدواژه ها:

medical image processing ، Discrete Wavelet transform ، Noise Reduction ، Edge-Preserving Filter ، Retinal Layers ، Optical coherence tomography