<div dir="ltr">DICOM data is often signed after the slope/intercept in applied. Try setting the type to short rather than unsigned short.</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Aug 12, 2013 at 9:48 AM, Bradley Lowekamp <span dir="ltr"><<a href="mailto:blowekamp@mail.nih.gov" target="_blank">blowekamp@mail.nih.gov</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Do you have the code to share so that it can be easily reproduced?<br>
<br>
<br>
Thanks,<br>
Brad<br>
<div class="HOEnZb"><div class="h5"><br>
On Aug 12, 2013, at 9:33 AM, Constantine Zakkaroff <<a href="mailto:mnkz@leeds.ac.uk">mnkz@leeds.ac.uk</a>> wrote:<br>
<br>
> Hello ALL,<br>
><br>
> I'm wondering if anyone can explain what's going on with the changing image intensities in a read-write-read round-trip. I think it's a bug, but the <a href="http://issues.itk.org" target="_blank">issues.itk.org</a> is unresponsive at the moment. Another bug? ;)<br>
><br>
> Anyhow, the strange thing is that the results for the round trip read-write-read test are very different for ITK 3.20 and ITK 4.4.1.<br>
><br>
> I use to StatisticsImageFilter to examine the intensity values. Here's what happens, when I simply read a DICOM image, print stats, save the image and read it again, followed by printing the stats:<br>
><br>
> ITK Version: 3.20<br>
> Stats for original file:<br>
> Min: 0, Max: 2474, Mean: 169.236, Sigma: 256.719, Variance: 65904.7, Sum: 1.40371e+007<br>
> Stats for saved file:<br>
> Min: 0, Max: 2471, Mean: 167.132, Sigma: 256.125, Variance: 65600.1, Sum: 1.38626e+007<br>
><br>
> ITK Version: 4.4<br>
> Stats for original file:<br>
> Min: 0, Max: 2474, Mean: 169.236, Sigma: 256.719, Variance: 65904.7, Sum: 1.40371e+007<br>
> Stats for saved file:<br>
> Min: 0, Max: 7446, Mean: 509.114, Sigma: 772.59, Variance: 596895, Sum: 4.22279e+007<br>
><br>
> In both cases the code is identical. Just compiled against different versions of ITK. The images are read and written as itk::Image<unsigned short, 3>, with no processing, no changes to any aspect of the images.<br>
><br>
> So, ITK 3.20 introduces a small change, which I'm pretty sure shouldn't be there. But in ITK 4.4.1 the scale of intensities changes three-fold.<br>
><br>
> I'd not be surprised by a change of this magnitude if I was photocopying those images, but not when using digital software and hardware. :^) Is there something I'm not understanding here?<br>
><br>
> None of this happens with read(DICOM)-write(MHD)-read(MHD), where the original and round-trip values are identical:<br>
> Stats for saved file: file0.mhd<br>
> Min: 0, Max: 2474, Mean: 169.236, Sigma: 256.719, Variance: 65904.7, Sum: 1.40371e+007<br>
><br>
> Many thanks,<br>
> Constantine<br>
><br>
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