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<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'>Hi
Hongwei,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'>If
you want to “turn off” the attenuation information you don’t need to define the
phantom! You just need to define the source (shape; type of source;
distribution of the emission; placement of the source…).<br>
And, if you want to “turn off” the physical effects (positron range, scattering
and photon accolinearity) you may use the gamma/gamma emission source.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'>This
choice (of these 2 turn off) allow to produce simulated data representing an “acquisition
best case scenario”.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#262626'>Susana Branco Silva<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Comic Sans MS";
color:#E36C0A'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:navy'><img width=239
height=35 id="Picture_x0020_1" src="cid:image001.gif@01C8A73A.EA167060"
alt=untitled><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Calibri","sans-serif";
color:#595959'>Faculdade de Ciências da Universidade de Lisboa<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Calibri","sans-serif";
color:#595959'>Campo Grande, 1749-016 Lisboa, Portugal<br>
Phone: (+351) 21 750 01 77 ext.: 20515<br>
Fax: (+351) 21 750 00 30<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Calibri","sans-serif";
color:#7F7F7F'><a href="mailto:susana.silva@fc.ul.pt"><span lang=FR
style='color:#595959;text-decoration:none'>email: </span><span lang=FR
style='color:blue'>susana.silva@fc.ul.pt</span></a></span><span lang=FR
style='font-size:8.0pt;font-family:"Calibri","sans-serif";color:#7F7F7F'><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:8.0pt;font-family:"Calibri","sans-serif";
color:#595959'>url: </span><u><span lang=EN-US style='font-size:8.0pt;
font-family:"Calibri","sans-serif";color:#7F7F7F'><a href="www.ibeb.fc.ul.pt"><span
style='color:blue'>www.ibeb.fc.ul.pt</span></a></span></u><span lang=EN-US
style='font-size:8.0pt;font-family:"Calibri","sans-serif";color:#7F7F7F'><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:8.0pt;font-family:"Calibri","sans-serif";
color:#1D1B11'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Comic Sans MS"'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> gate-users-bounces@lists.healthgrid.org
[mailto:gate-users-bounces@lists.healthgrid.org] <b>On Behalf Of </b>Hongwei Ye<br>
<b>Sent:</b> sábado, 26 de Abril de 2008 0:14<br>
<b>To:</b> gate-users@lists.healthgrid.org<br>
<b>Subject:</b> [Gate-users] about attenuation and sensitivity in GATE<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Dear All,</span>
<br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I'm wondering
if there is any way to turn off the attenuation in GATE (because I'd like to
use a simulation without attenuation in reconstruction). </span><br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>What I did
right now is to use "Air" to replace "Water" (or something
else) for the object material. But I met a problem here:</span> <br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I have tested
two simulations: same objects with same activity, same scan time, but
simulation 1 is made by "Air" and simulation 2 is made by
"Water". Guess what I got? Simulation 2 (13920 counts) had more
coincidences than simulation 1 (8646 counts) even if simulation 2 was supposed
to be attenuated more by water. (I attached .mac file here)</span> <br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Can anyone
explain this phenomena or guide me how to turn off the attenuation ? Should I
use "Vacuum" instead of "Air" and set up "back to back
gamma source"? </span><br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>One more
question is about the sensitivity: what is its range for ECAT 962 system? By
roughly calculating, I got 20~50 cps/kBq depending on different objects. It
seems to me those number are too high.</span> <br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Thanks a lot.</span>
<br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Regards,</span>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Hongwei</span> <br>
<br>
<br>
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