<div dir="ltr">Honorable Maxime, <div><br></div><div>Thank you very much for your reply and your knowledge. You always give the best suggestion and answers. I definitely have spent much time on digitizer setting, such as singles readout level, deadtime (and deadtime volume), delay, coincidence window and delay window width, function modality (non/paralysable ). I experimented with these parameters for many times, and also validated it against our real data. From the comparison, these settings seem to be alright, but the GATE model gives me more counts (~25%) than the real system. </div><div><br></div><div>One thing worth noticing is that the NEMA sensitivity experiment uses a very low dose (500 uCi). Under such a low count rate, it sounds easy to figure out why GATE has more counts because detector is not saturated and deadtime bearly kick off, but I have been stuck for about half a month already on this point. </div><div><br></div><div>Another point is that does GATE simulate Lu167 decay/deexcitations in its LSO and LYSO material when the material is called in GATE? If not, how can I add it to my simulation? Sorry about asking this question before doing my own research on this topic. </div><div><br></div><div>I will update this topic if I find something interesting regarding this discrepancy between GATE simulation and the real system. </div><div>Thank you very much for your time and excellent expertise. <br></div><div><br></div><div>Cheers. </div><div>Have a mellow weekend. </div><div><br></div><div>Zhengzhi </div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, May 29, 2020 at 7:52 PM Maxime Toussaint <<a href="mailto:Maxime.Toussaint@usherbrooke.ca">Maxime.Toussaint@usherbrooke.ca</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Greetings,</div>
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That is a tricky question. Sadly, I do not know if such a convenient procedure is available within Gate. While I do not have much experience in modeling an accurate acquisition system, I can offer a couple of ideas which might be useful or not.</div>
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In my humble belief, the trickiest part of your task is to define the digitizer [1] and I think it might also be where the discrepancy appear. If you want a realistic model, you should have a pretty complex digitizer that exploit most of the available module.
For example, having underestimated the Dead Time could explains what you see. It could also be due to a mismatch in the depth designation of the digitizer module: setting the DeadTime on crystal level allow more events then allowing it on module level. Thus,
the only advice I can give you is to make sure that your digitizer configuration correspond to the scanner by validating each module if possible. If any of the digitizer module do not have what you need, maybe some more advanced Gate Users could provide a
solution! </div>
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Have a nice day and good luck,</div>
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Maxime Toussaint</div>
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[1] <a href="https://opengate.readthedocs.io/en/latest/digitizer_and_detector_modeling.html?highlight=pileup#digitizer-modules" target="_blank">https://opengate.readthedocs.io/en/latest/digitizer_and_detector_modeling.html?highlight=pileup#digitizer-modules</a><br>
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<div id="gmail-m_1998846352167205861divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>De :</b> Gate-users <<a href="mailto:gate-users-bounces@lists.opengatecollaboration.org" target="_blank">gate-users-bounces@lists.opengatecollaboration.org</a>> de la part de Albert Grace Lieu <<a href="mailto:albertnew2018@gmail.com" target="_blank">albertnew2018@gmail.com</a>><br>
<b>Envoyé :</b> 29 mai 2020 13:32<br>
<b>À :</b> gate-users <<a href="mailto:gate-users@lists.opengatecollaboration.org" target="_blank">gate-users@lists.opengatecollaboration.org</a>><br>
<b>Cc :</b> Peter Olcott <<a href="mailto:polcott@reflexion.com" target="_blank">polcott@reflexion.com</a>><br>
<b>Objet :</b> [Gate-users] Divergence between GATE simulation and the reality</font>
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<div dir="ltr">Dear GATE users,
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<div>I have modeled a real PET system in GATE as close to the real system as I can. However, during the noise equivalent count collaboration, GATE is always much better (about 50%) than the real system. After lots of effort, we looked at the results of the
NEMA sensitivity experiment (very low dose, ~500 uci) and found that GATE collected about 25% more counts than the real system. </div>
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<div>I was wondering if there is some calibration work done between GATE simulation and reality. Could someone give any help on how to further debug or make clear what causes this discrepancy between simulation and reality? </div>
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<div>Thanks a lot. </div>
<div>Zhengzhi</div>
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