An Exploratory Analysis of Impulse Noise Filters on X-Ray Phantom Images

Radiography or X-ray imaging is a diagnostic imaging used in medicine to produce images of inner anatomical structures such as bones, teeth, lungs, and chest organs. Impulse noise is one of the major factors that degrade the visual quality of X-ray images. In the literature, there is no method or proper guidance available to assess the performance of edge-preserving noise removal filters designed for impulse noise removal on X-ray images. There are a number of theoretical edge-preserving denoising filters capable of removing impulse noise from X-ray images. In this work, the relative merits of existing impulse noise removal filters designed for X-ray modalities are assessed. The assessment is done based on subjective and objective evaluations. For objective evaluation, image quality assessment metrics like Peak Signal-to-Noise Ratio (PSNR) and Edge Preservation Index (EPI) are used. Subjective evaluation is done based on the Visual Quality Assessment Score (VQAS). In subjective evaluation and objective evaluation, the Noise Accumulation and Harmonic Analysis Technique (NAHAT) showed high scores compared to other filters. Equally good performance is exhibited by the Iterative Mean Filter (IMF) and the Different Applied Median Filter (DAMF). This may be used as guidance for the proper selection of edge-preserving impulse noise filters for the quality control of X-ray images. It may also be utilized for the design of an automated technique for impulse noise removal in X-ray imaging.