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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">Hello all,</span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">I am trying to do a spatial resolution study using Iodine - 131 (364 keV energy)
for a SPECT sytem. <font size="3"><span style="font-size: 12pt;">I am using</span></font><font size="3"><span style="font-size: 12pt;"> a high energy collimator, based on specifications that I have (septal thickness - 2mm, hole diameter (across hexagon flats)
- 4 mm, hole length - 59.7mm, number of holes - 8000 and source - collimator surface distance - 10cm).</span></font></span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;"><br>
</span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">I have modeled the HE collimator within the GATE environment exactly as stated
in the specifications. However, when performing the resolution study, I do not get the 13.4 mm spatial resolution that is stated in the specifications. I have fitted a Gaussian curve to the data I get from my simulation in order to determine the FWHM but the
resolution I get is way worse than the desired one. </span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;"><br>
</span></font></div>
<div style="font-family: Calibri, Helvetica, sans-serif, serif, EmojiFont; font-size: 16px; margin-top: 0px; margin-bottom: 0px;">
<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">Normally when the resolution is bad, collimator parameters such as the hole
length, the hole diameter or source-collimator distance need to be modified, but since those are fixed from the specifications I cannot really change them.</span></font></div>
<div style="font-family: Calibri, Helvetica, sans-serif, serif, EmojiFont; font-size: 16px; margin-top: 0px; margin-bottom: 0px;">
<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">I tried to increase the density of the septa (lead) in order to reduce any
septal penetration but even though the resolution was improved, I still did not get the one from the specifications. </span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;"><br>
</span></font></div>
<div style="font-family: Calibri, Helvetica, sans-serif, serif, EmojiFont; font-size: 16px; margin-top: 0px; margin-bottom: 0px;">
<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">Do you have any ideas or suggestions of what I could try?</span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;"><br>
</span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">Best Regards </span></font></div>
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<font face="Calibri,Helvetica,sans-serif,EmojiFont,Apple Color Emoji,Segoe UI Emoji,NotoColorEmoji,Segoe UI Symbol,Android Emoji,EmojiSymbols" size="2"><span style="font-size: 16px;">Anestis</span></font></div>
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