<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><div dir="auto"><div>Hello Ashok, </div><div dir="auto"><br></div><div dir="auto">I believe your problem isn't gate normalising activity but rather that by setting a fixed number of primaries you are defining the number of photons generated, so the intensity information is not used to limit photon emissions, just to set relative intensity of each photon. The difference in counts will thus just be the difference in detection efficiency for the photons, which with similar energies will be about the same, giving you about the same counts as you mention. Therefore I see 2 options:</div><div dir="auto">1) replace the fixed number of primaries with a source of known activity. Then your counts from each simulation should be the proportion of counts from each photon "type" (high energy and main emmision). Someone else could comment to correct me if this is wrong and set intensities are still normalised, but I would be surprised if they were in the case of a fixed activity source. An easier approach exists where this doesn't matter however...</div><div dir="auto">2). Use your existing data to calculate what you need. The count rate, C, in the detector from photons of energy E will be related to the activity of the source, A, the emission probability, I, and the detection efficiency, D, by the equation:</div><div dir="auto">C=AID</div><div dir="auto">What you are looking for is the ratio of: C(E=159 keV) to C(E>159 keV). So </div><div dir="auto">AID (for E = 159 keV) / AID (for E > 159 keV). </div><div dir="auto">As the photos come from the same source A is a constant so we can cancel that out. I is the emmision intensities, which you know (0.83 for E = 59 kev and 0.03 for E > 159 kev) and your simulation will give you D for each energy if you divide the number of counts you record by the number of primaries you used. The above ignores geometry of the emissions , but I am assuming their angular emission profile is the same and isotropic. I have also assumed the set number of primaries completely overrides the set intensities except to ensure each is in proportion to each other. If you have any doubt of this (or if someone else corrects me) then you could just run a simulation for each individual energy without setting emission intensity (all at 100%) at the same number of primaries to get D for each energy and you know I for each energy already.</div><div dir="auto"><br></div><div dir="auto">I hope this helps.</div><div dir="auto"><br></div><div dir="auto">Olie</div><div dir="auto"><br><div class="gmail_extra" dir="auto"><br><div class="gmail_quote">On 8 Apr 2022 05:00, gate-users-request@lists.opengatecollaboration.org wrote:<br type="attribution"><blockquote class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">Send Gate-users mailing list submissions to<br>
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<p dir="ltr">Today's Topics:</p>
<p dir="ltr"> 1. how to get proportionate number of photons detection<br>
(Ashok Tiwari)<br></p>
<p dir="ltr">----------------------------------------------------------------------</p>
<p dir="ltr">Message: 1<br>
Date: Fri, 8 Apr 2022 05:03:13 +0000 (UTC)<br>
From: Ashok Tiwari <tiwarias@yahoo.com><br>
To: Gate-users <gate-users@lists.opengatecollaboration.org><br>
Subject: [Gate-users] how to get proportionate number of photons<br>
detection<br>
Message-ID: <234704160.1728448.1649394193916@mail.yahoo.com><br>
Content-Type: text/plain; charset="utf-8"</p>
<p dir="ltr">Dear GATE users,<br>
I tried to simulate the I-123 photons spectrum (a) using only 159 keV photon (83.3%) in one simulation and (b) all other high energy photons greater than 159 keV (~3%) in another simulation. <br>
In both of my simulations, I simulated a fixed number of primaries (decays) so that I could estimate the contribution of 159 keV and high energy photons separately. However, by defining the sources (see below), a similar number of photons have been detected in both simulations! This is undesirable as the intensity of their emissions are hugely different, as defined in the lines below. It looks like GATE normalized the intensity value (probability of emission); as a result of that, I may end up getting similar results for both simulations. Now, my question is, how can I define the sources in (b) to get a proportionate number of photons detection? If my assumption is right about normalization, is it possible to force GATE not to normalize the intensity values in (b)?</p>
<p dir="ltr">For (a) I define the following lines of code in my simulation settings:<br>
/gate/source/addSource src1 gps<br>
/gate/source/src1/gps/particle gamma/gate/source/src1/gps/energytype Mono/gate/source/src1/gps/ene/mono 158.97 keV<br>
/gate/source/src1/setIntensity 0.833/gate/source/src1/gps/angtype iso/gate/source/src1/gps/type Point/gate/source/src1/gps/centre 0. 0. 0. mm/gate/source/src1/attachTo src_1/gate/source/list</p>
<p dir="ltr">For (b) I selected 5 major gamma emissions having energy greater than 159 keV:/gate/source/addSource src1 gps/gate/source/src1/gps/particle gamma/gate/source/src1/gps/energytype Mono/gate/source/src1/gps/ene/mono 346.35 keV<br>
/gate/source/src1/setIntensity 0.00125783/gate/source/src1/gps/angtype iso/gate/source/src1/gps/type Point/gate/source/src1/gps/centre 0. 0. 0. mm/gate/source/src1/attachTo src_1<br>
/gate/source/addSource src2 gps/gate/source/src2/gps/particle gamma/gate/source/src2/gps/energytype Mono/gate/source/src2/gps/ene/mono 440.02 keV<br>
/gate/source/src2/setIntensity 0.00428162/gate/source/src2/gps/angtype iso/gate/source/src2/gps/type Point/gate/source/src2/gps/centre 0. 0. 0. mm/gate/source/src2/attachTo src_1<br>
/gate/source/addSource src3 gps/gate/source/src3/gps/particle gamma/gate/source/src3/gps/energytype Mono/gate/source/src3/gps/ene/mono 505.33 keV<br>
/gate/source/src3/setIntensity 0.00315707/gate/source/src3/gps/angtype iso/gate/source/src3/gps/type Point/gate/source/src3/gps/centre 0. 0. 0. mm/gate/source/src3/attachTo src_1<br>
/gate/source/addSource src4 gps/gate/source/src4/gps/particle gamma/gate/source/src4/gps/energytype Mono/gate/source/src4/gps/ene/mono 528.96 keV<br>
/gate/source/src4/setIntensity 0.013911/gate/source/src4/gps/angtype iso/gate/source/src4/gps/type Point/gate/source/src4/gps/centre 0. 0. 0. mm/gate/source/src4/attachTo src_1<br>
/gate/source/addSource src5 gps/gate/source/src5/gps/particle gamma/gate/source/src5/gps/energytype Mono/gate/source/src5/gps/ene/mono 538.54 keV<br>
/gate/source/src5/setIntensity 0.00381514/gate/source/src5/gps/angtype iso/gate/source/src5/gps/type Point/gate/source/src5/gps/centre 0. 0. 0. mm/gate/source/src5/attachTo src_1<br>
Any help is highly appreciated. Thanks in advance.<br>
Regards,Ashok <br>
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