<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
        {font-family:"Cambria Math";
        panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
        {font-family:Calibri;
        panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
        {margin:0cm;
        text-align:right;
        direction:rtl;
        unicode-bidi:embed;
        font-size:11.0pt;
        font-family:"Calibri",sans-serif;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
        {mso-style-priority:34;
        margin-top:0cm;
        margin-right:36.0pt;
        margin-bottom:0cm;
        margin-left:0cm;
        text-align:right;
        direction:rtl;
        unicode-bidi:embed;
        font-size:11.0pt;
        font-family:"Calibri",sans-serif;}
span.EmailStyle17
        {mso-style-type:personal-compose;
        font-family:"Calibri",sans-serif;
        color:windowtext;}
span.highlighted
        {mso-style-name:highlighted;}
.MsoChpDefault
        {mso-style-type:export-only;}
@page WordSection1
        {size:612.0pt 792.0pt;
        margin:72.0pt 90.0pt 72.0pt 90.0pt;}
div.WordSection1
        {page:WordSection1;}
/* List Definitions */
@list l0
        {mso-list-id:172301782;
        mso-list-type:hybrid;
        mso-list-template-ids:-48596956 67698703 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l0:level1
        {mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level2
        {mso-level-number-format:alpha-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level3
        {mso-level-number-format:roman-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:right;
        text-indent:-9.0pt;}
@list l0:level4
        {mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level5
        {mso-level-number-format:alpha-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level6
        {mso-level-number-format:roman-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:right;
        text-indent:-9.0pt;}
@list l0:level7
        {mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level8
        {mso-level-number-format:alpha-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:left;
        text-indent:-18.0pt;}
@list l0:level9
        {mso-level-number-format:roman-lower;
        mso-level-tab-stop:none;
        mso-level-number-position:right;
        text-indent:-9.0pt;}
ol
        {margin-bottom:0cm;}
ul
        {margin-bottom:0cm;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<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>
</div>
</body>
</html>