title: Geometric nonlinear diffusion filter and its application to X-ray imaging.
abstract: BACKGROUND
  Denoising with edge preservation is very important in digital x-ray imaging since it may allow us to reduce x-ray dose in human subjects without noticeable degradation of the image quality. In denoising filter design for x-ray imaging, edge preservation as well as noise reduction is of great concern not to lose detailed spatial information for accurate diagnosis. In addition to this, fast computation is also important since digital x-ray images are mostly comprised of large sized matrices.
  
  
  METHODS
  We have developed a new denoising filter based on the nonlinear diffusion filter model. Rather than employing four directional gradients around the pixel of interest, we use geometric parameters derived from the local pixel intensity distribution in calculating the diffusion coefficients in the horizontal and vertical directions. We have tested the filter performance, including edge preservation and noise reduction, using low dose digital radiography and micro-CT images.
  
  
  RESULTS
  The proposed denoising filter shows performance similar to those of nonlinear anisotropic diffusion filters (ADFs), one Perona-Malik ADF and the other Weickert's ADF in terms of edge preservation and noise reduction. However, the computation time has been greatly reduced.
  
  
  CONCLUSIONS
  We expect the proposed denoising filter can be greatly used for fast noise reduction particularly in low-dose x-ray imaging.
authors.affiliation: Department of Biomedical Engineering, Kyung Hee University, 1 Seocheon, Yongin, Gyeonggi 446-701, Korea.
authors.forename: Eric
authors.initials: E
authors.lastname: Michel-González
authors.forename: Min Hyoung
authors.initials: MH
authors.lastname: Cho
authors.forename: Soo Yeol
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000818:Animals; D004058:Diffusion; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D017711:Nonlinear Dynamics; D011859:Radiography / Q000379:methods*; D051381:Rats; D013997:Time Factors; D055114:X-Ray Microtomography / Q000379:methods