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<div class="moz-cite-prefix">Hi Michael,<br>
<br>
To complete Thibaut's answer:<br>
- the scatter amount is given as a rate in counts/sec. The
"counts" refer to a raw number of scatter counts for this given
bin (directly comparable to the prompts). A rate is needed for the
generalization when we reconstruct from a list-mode for which the
time frames are not predefined, so it is flexible.<br>
- the normalization factor is optional and in SPECT it can be
used for pixelated detectors like CZT-based detectors to normalize
for variable efficiency from a pixel to another.<br>
<br>
Finally, in CASToR, we took the decision to always consider
additive contributions part of the model (added to the forward
projection) and all multiplicative corrections are also combined
within the system matrix elements. This corresponds to the
"Ordinary Poisson" model. However, you are still allowed to
provide any value in the "Amount of data in the bin" field.<br>
<br>
Cheers<br>
Simon<br>
<br>
Le 28/04/2017 à 13:18, tmerlin a écrit :<br>
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<p>Hi Michael,</p>
<p>The scatter rate is normalized by the frame/acquisition
duration in seconds (if provided) and added to the forward
projection value. The normalization factor is a multiplicative
correction factor applied during forward & backward
projection.</p>
<p>Best regards,</p>
<p>Thibaut Merlin</p>
<br>
<div class="moz-cite-prefix">On 26/04/2017 18:53, Michael
Ljungberg wrote:<br>
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<p class="MsoNormal">Hi all</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Look like my conversion program works
now. I also got the attenuation correction to work. Simind
and Castor has a different orientations so I solved this by
starting at 180 degrees instead of flipping the end result.
This also aligned to the orientation of the attenuation map.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have a question concerning the scatter.
The value I add to the *.cdf file – is it added in the
forward projector or is it subtracted in some way? I assume
the scatter value should be normalised to the total value I
also add.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Second question – what does the
“ Normalization factor of the corresponding sinogram bin“
value actually do in SPECT histograms?</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Michael <o:p></o:p></p>
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<pre class="moz-signature" cols="72">--
Thibaut MERLIN -- PhD
Docteur en Imagerie Médicale au Laboratoire de Traitement de l'Information Medicale (LaTIM - INSERM UMR 1101)
Bâtiment 1
CHRU Morvan - 2, Av. Foch
29609 Brest CEDEX - FRANCE
Tel: 06.75.12.24.90</pre>
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