title: Access and remove negative pixels
body: <p>How should I approach the problem of removing negative pixels from MRI slices (or any image)?</p>
  
  <p>Also, it would really help if someone can briefly explain why they occur.</p>
  
  <p>I have read many online references especially those on MATLAB forum, but they seem to have diverse reasons as to why they occur.</p>
  
  <p>Sorry, I don't have a code to post, since I am figuring out my approach yet.   </p>