Posted by
Gino Canessa on
Oct 16, 2006; 2:41am
URL: http://imagej.273.s1.nabble.com/measurements-using-MRI-jpg-images-tp3701304p3701306.html
My guess would be that there is no calibration reference for the JPEG images
(e.g., it is measuring pixels), whereas the DICOM images have calibration so
that measurements can be converted into more useful numbers (e.g., mm).
If you are just measuring pixels on both, as Gabriel said, there are
artifacts introduced by the JPEG conversion.
All of this assumes, of course, that by saying "jpg," you mean an actual
JPEG, instead of a JPEG compressed DICOM. If you are using a JPEG
compressed DICOM image, and the compression was set to lossless, there
should be no differences.
Hope this helps,
Gino
P.s., Just like to re-enforce Gabriel's mention that JPEG images should not
be used for analysis of anything (again, barring the lossless types common
in DICOM, et all).
On 10/15/06 4:54 PM, "Gabriel Landini" <
[hidden email]> wrote:
> On Sunday 15 October 2006 06:43, John Dufton wrote:
>> I have a question regarding measurements on mri images.
>> I have saved a number of images as jpg images. The measurements on these
>> jpg images do not seem to correspond to measurements on the workstation.
>
> Hi,
> Jpeg compressed images should not be used for serious imaging purposes.
> The compression in the jpegs is lossy, so I guess that you may be measuring
> some amount of artifacts rather than the data.
>
> Instead, you can save your images as Tiff or Png.
>
> Cheers.
>
> Gabriel
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Gino Canessa
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