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<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">Hi all,<o:p></o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed"><o:p> </o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">I'm trying to add a I-131 source to a SPECT system, and I've tried to simulate it in three different ways:<o:p></o:p></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-right:0cm;text-align:left;mso-list:l0 level1 lfo1;direction:ltr;unicode-bidi:embed">
I added a source with energy type Mono, i.e. mono-energy of 364keV.<o:p></o:p></li><li class="MsoListParagraph" style="margin-right:0cm;text-align:left;mso-list:l0 level1 lfo1;direction:ltr;unicode-bidi:embed">
I added a <span class="highlighted">UserSpectrum</span> energy type, with a Discrete Spectrum file, that contains the emission in 364keV (written in the file as 0.364).<o:p></o:p></li><li class="MsoListParagraph" style="margin-right:0cm;text-align:left;mso-list:l0 level1 lfo1;direction:ltr;unicode-bidi:embed">
I added a <span class="highlighted">UserSpectrum</span> energy type, with a Discrete Spectrum file, that contains all the emissions of I-131 (written similarly to the previous file, with all the lines probability weighting).<o:p></o:p></li></ol>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed"><o:p> </o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">The first two simulations give me a very similar energy spectrum (both in the output window, and in the whole spectra), but I detect half the amount of photons with the UserSpectrum
compared to the mono-energy.<o:p></o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">On the other hand, when I compare the detected photons ratio between the full emissions simulation to the mono-energy simulation, the ratio is 0.89 (which makes much more sense).<o:p></o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed"><o:p> </o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">Have anyone ever encountered this issue?<o:p></o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed"><o:p> </o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">Thank you,<o:p></o:p></p>
<p class="MsoNormal" style="text-align:left;direction:ltr;unicode-bidi:embed">Ayeleth Devir-Wolfman.<span lang="HE" dir="RTL" style="font-family:"Arial",sans-serif"><o:p></o:p></span></p>
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