STUDY OF FILTRATION TECHNIQUES TO REMOVE SALT AND PEPPER NOISE ON CT SCAN IMAGES

• Main Author: Sofa Amatullah, Fadilla
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/60598
• Institution: Institut Teknologi Bandung

Image reconstruction on CT Scan is currently developing a lot, both in terms of quality and duration of irradiation. Various methods have been applied for the image reconstruction process. Filtered Back Projection (FBP) is one of the method that is quite widely used. In this final project, the filtered back projection (FBP) based method was chosen in the image reconstruction algorithm. FBP is the basis of the algorithm that is currently being developed in CT scans. FBP applies a filtered back projection method that overcomes the blur in the image. Two different types of phantoms were used as reconstruction objects, namely virtual test phantoms and CT scan projections. The virtual test phantom used consisted of a circle phantom measuring 128 128 pixels and a shepp logan phantom measuring 512X 512 pixels. The phantom test results from CT Scan data projections are abdominal projection data measuring 512X 512X 361 voxels. The software used to design the image reconstruction algorithm in this study is MATLAB R2020b. The pre-processing filters used in this research are Ram-Lak, Hamming, and Hanning filters. To test the quality of the reconstructed image, the calculation of PSNR (Peak Signal to Noise Ratio) is used. In the experiments that have been carried out, it is found that the Hamming and Hanning filters are better applied to the image reconstruction process than the Ram-Lak filter both in the frequency domain and in the spatial domain because they produce image quality with a larger PSNR value. In the reconstruction process, noise usually appears in the resulting image. Noise reduces the quality of the resulting image so that it can interfere with the reading of the diagnostic results on the patient's body. One type of noise that can appear after image reconstruction is salt and pepper noise. There are many methods that can be used to remove salt and pepper noise, but the best one is the median filter. Therefore, in this study, an analytical study of the application of the median filter was carried out on images that were added with salt and pepper noise with different noise ratios. To test the quality of the image resulting from the application of the median filter, an image quality test was performed using the PSNR value. The results obtained are the greater the noise ratio, the lower the quality of the median filter in removing salt and pepper noise. This can be seen from the decrease in the percentage change in image quality and the small PSNR value.