<div dir="ltr"><div><div>Hi,<br></div>Thanks for pointing this out. The scatter images should be accurate but the primary image are indeed wrong (and I understand it's probably useless to have the scatter images without primary).<br>For the point source, you should get a warning letting you know of this:<br><a href="https://github.com/OpenGATE/Gate/blob/develop/source/digits_hits/src/GateFixedForcedDetectionActor.cc#L1490">https://github.com/OpenGATE/Gate/blob/develop/source/digits_hits/src/GateFixedForcedDetectionActor.cc#L1490</a><br></div><div>We will add a check on the shape of the source to allow only rectangular shapes.<br></div><div>If you need those sources, you can correct the code to account for these source types, the problem should be handled in the <span class="gmail-pl-en">PrimaryFluenceWeighting function.<br></span></div><div><span class="gmail-pl-en">Simon<br></span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, May 5, 2017 at 3:06 PM, Triltsch, Nicolas <span dir="ltr"><<a href="mailto:nicolas.triltsch@tum.de" target="_blank">nicolas.triltsch@tum.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<p>Hello Gate fellows,</p>
<p>I noticed some bugs concerning the choice of the source when
using the Fixed Forced Detection Actor (FFDA). As I can remember,
the FFDA needs a focused source spot to work properly. In the
example folder of Gate, the source was chosen to be a rectangle
and in this case the simulation works properly. However, if
different source types are tested the simulation gives strange
results.<br>
</p>
<p>I tried two different source types: Firstly, I changed the shape
of the source to be a circle and secondly, I took a point source.
I will explain the bugs I could notice in both cases.</p>
<p><b>1) Focused circle source:</b> Primary image and flatfield give
nan. The Compton and Rayleigh scatter images are calculated, but
depend on the number of simulated photons as the can not be
normalized by an appropriate flatfield of nan's.</p>
<p>---primary and flatfield---</p>
<p><img src="cid:part1.041C2815.84F7718C@tum.de" alt=""></p>
<p>---compton---<br>
</p>
<p><img src="cid:part2.CF659835.58428629@tum.de" alt=""></p>
<p>---rayleigh---<br>
</p>
<p><img src="cid:part3.1E5164B7.25A154F5@tum.de" alt=""></p>
<p><b>2) Point source:</b> The primary image seems correct. However,
the scatter images can not be calculated correctly, as they show a
scatter-to-flatfield ratio of 80% for Compton and 40% Rayleigh.
These values are impossible in the given simulation setup where I
expect scatter ratios of around 1-2% (as verified with the
experiment). I noticed that the ratios depend on the number of
simulated photons which shouldn't be the case after flatfield
normalization.<br>
</p>
<p>---primary/ff---<br>
</p>
<p><img src="cid:part4.9087BD46.48F524D0@tum.de" alt=""></p>
<p>---compton/ff---<br>
</p>
<p><img src="cid:part5.024B1629.62FA88B0@tum.de" alt=""></p>
<p>---rayleigh/ff---<br>
</p>
<img src="cid:part6.3ECB3522.141AD546@tum.de" alt=""><br>
<br>
<b>Conclusion:<br>
</b>It seems that the FFDA only works if the source is chosen to be
a focused rectangle and is bugy if other source types (circle or
point source, maybe other types) are given.<b><br>
<br>
Can anyone comment on this behavior?<br>
<br>
</b>See the used scripts attached.<br>
<br>
Regards,<br>
Nico<br>
<pre class="m_-800194081298017870moz-signature" cols="72">--
B.Sc. Nicolas Triltsch
Masterand
Technische Universität München
Physik-Department
Lehrstuhl für Biomedizinische Physik E17
James-Franck-Straße 1
85748 Garching b. München
Tel: <a href="tel:+49%2089%2028912591" value="+498928912591" target="_blank">+49 89 289 12591</a>
<a class="m_-800194081298017870moz-txt-link-abbreviated" href="mailto:nicolas.triltsch@tum.de" target="_blank">nicolas.triltsch@tum.de</a>
<a class="m_-800194081298017870moz-txt-link-abbreviated" href="http://www.e17.ph.tum.de" target="_blank">www.e17.ph.tum.de</a></pre>
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