Thursday, July 2, 2009

DullRazor

Recently, there has been an increase in the number of studies using image processing techniques to analyze melanocytic lesions for atypia and possible malignancy, and for total-body mole mapping. Such lesions, however, can be partially obscured by body hair; and, to date, no study has fully addressed the problem of human hair occluding imaged lesions. In a previous study we designed an automatic segmentation program to differentiate skin lesions from normal healthy skin.  Our program performed well with most images — the exception being images where dark thick hair covers part of the lesions. Dark hair confused the program which resulted in unsatisfactory segmentation results.

Presented here is a method to remove hair from images using a pre-processing program called DullRazor.   DullRazor performs the following steps:

  1. It identifies the dark hair locations by a generalized grayscale morphological closing operation,
  2. It verifies the shape of the hair pixels as thin and long structure, and replace the verified pixels by a bilinear interpolation, and
  3. It smooths the replaced hair pixels with an adaptive median filter.

The algorithm has been implemented in C on a SunOS 4.x workstation. (The program can be run on Sun Solaris workstations as well.) It has been tested on real nevi images with satisfactory results. Figure 1. shows a lesion covered by thick hair and Figure 2. shows the result with hair removed. The man.txt file provides more details.

 

DullRazor can be downloaded and used without fee for non-commerical purpose.  The full license is included in the download.

Download the Unix version of DullRazor (dullrazor.zip, 87KB): follow this link.
Download the Windows version of DullRazor (dullrazor_wins.zip, 327KB): follow this link.

http://www.dermweb.com/dull_razor/

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