Posted by
Christophe CHAMOT on
Jan 17, 2006; 9:02am
URL: http://imagej.273.s1.nabble.com/Ratio-and-Background-substraction-operations-tp3704031p3704038.html
Michael Cammer a écrit :
> With fluorescence where the intensity is directly proportional to the
> number of molecules and the detector is linear (e.g. CCD camera), then
> division after flatfield correction (if necessary) and background
> subtraction is the correct method.
>
Hello,
Just as a remark, in biology applied microscopy, fluorescence is not so
proportional to the number of molecules. One knows that environment of
the dye could have a dramatic inluence on quantum efficiency (presence
of quenchers, pH differences inducing spectral modifications,... in the
different cell compartments).
I agree for all the other considerations ;-)
>
>
>>I think that you are right in the sense that it
>>depends on the detector. In case of MRI for
>>example the bias field is multiplicative,
>>therefore one must divide or subtract after log
>>transform. In the case of microscopy, it depends
>>on your acquisition camera.
>>
>>One way to test it, is to image a phantom with two
>>areas with a sharp contrast, and image a flat
>>background. By looking at some profiles you should
>>be able to figure it out.
>>
>>___________________________
>>
>>Olivier Salvado
>>Biomedical Engineering Department
>>Case Western Reserve University
>>
>>-----Original Message-----
>>From: ImageJ Interest Group
>>[mailto:
[hidden email]] On Behalf Of Vasseur
>>Monique
>>Sent: Thursday, January 12, 2006 10:26 AM
>>To:
[hidden email]
>>Subject: Ratio and Background substraction
>>operations
>>
>>My question is more mathematical or theoretical:
>>Whether the detector is logarithmic or linear in
>>output vs. light intensity, is it correct to do a
>>division to get a ratio image in both cases? Or
>>should it be a subtraction (?!) considering that
>>to remove the background from an image can be by
>>subtracting (if logarithmic detector) or dividing
>>(if linear detector)?
>>
>>
>>
>>Monique Vasseur
>>
>>Département de biochimie
>>
>>Université de Montréal
>>
>>
>>
>>
>>
>
>
>
> _________________________________________
> Michael Cammer
> Analytical Imaging Facility and
> Dept. ASB Biophotonics Innovation Laboratory
> Albert Einstein College of Medicine
> 1300 Morris Park Avenue, Bronx, NY 10461
> 718-430-2890 Fax 718-430-8996
> work:
http://www.aecom.yu.edu/aif/> personal:
http://coxcammer.com/>
--
CHAMOT Christophe
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