[Insight-users] Dicom Series Read Series Write: change in intensity values

[Mathieu Malaterre]

On Nov 20, 2007 6:13 PM, "Eliana M. Vásquez Osorio"
<e.vasquezosorio at erasmusmc.nl> wrote:
> Hello itk-users,
> I have a problem when writing (?) images series.  The intensity values
> change.
> This is what I did:
> - Read a series of dicom image into a volume
> - Write the volume out as another series of dicom files in a different
> folder.
> Since I do nothing in between (no filter is applied), I expected to get
> the same images after the writing process, but I found differences in
> the intensity values between the images.
>
> My input images use 12 bits for storing image info. (Bits Stored=12,
> 0028|0101 dicom tag).  The written image uses 16 bits.  I imagine that
> the intensity changes are related to this... but I don't get a clear
> idea how/why this changes the image that is produced.  Looking closely
> to the data, I found an offset of 1000 in the written images (compared
> to the original images).  Should I apply a filter to "correct" the 12
> bit to a 16 bit?  if so, which filter?  a casting filter?
>
> Any idea or suggestion is welcome! :)

This is in the  FAQ:

http://www.itk.org/Wiki/ITK_FAQ#DICOM:_Bits_Allocated.2C_Bits_Stored_and_High_Bit

Let me know if this makes any sense :)

-- 
Mathieu