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<div class="moz-cite-prefix">Hi,<br>
<br>
The reason is most likely the lack of normalization of your
sinogram data.<br>
<br>
In a realistic GATE simulation, even without independent crystal
efficiencies, each LOR has a different sensitivity, mostly due to
solid angles and energy threshold. These effects are due to the
geometry of the scanner and reflect this geometry in the
sensitivity image and in the reconstructions. So this should be
corrected for through a normalization scan.<br>
<br>
Check this IEEE MIC conference proceeding for more information:
<a class="moz-txt-link-freetext" href="https://ieeexplore.ieee.org/document/6153804">https://ieeexplore.ieee.org/document/6153804</a><br>
<br>
All the best !<br>
Simon<br>
<br>
Le 01/01/2019 à 04:14, Yanchao Huang a écrit :<br>
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<div>Dear Gate users,</div>
<div>Recently, I simulated a small animal PET scanner by
GATE 8.0. The scanner consists of 60 block-detectors in 5
contiguous rings. Each detector consists of 13X13 LYSO
crystals and each pixel size is 1.8X1.8X15 mm.</div>
<div>Firstly，an uniform cylindrical source was simulated and
the list-mode data in ASCII format was acquired. </div>
<div>Secondly, I reorganized the data onto histgram. Then
SSRB was applied to gain a 2-D data set. Thirdly, I
applied the 2-D ray tracing algorithm to generate the
system matrix simply. Each line of response(LOR) was
connected with the center of each crystal. And the
intersection length of the image pixel and the LOR was
considered as the detected probability. However, a
high-light artifact showed in the MLEM reconstructed
image. </div>
<div>I think this error may come from the sensitivity map
which also shows a spider-web shape distribution due to
the scanner geometric structure. But I don't know how to
deal with it. Does any one has ever meet such case? I‘m
very much looking for your help and suggestions.</div>
<div>By the way, Happy New Year to your all! </div>
<div>Best wishes!</div>
</div>
</div>
</div>
<br>
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