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<div class="moz-cite-prefix">Hi,<br>
<br>
The low sensitivity around the edges is completely normal as the
solid angle in PET decreases when you go near the detectors.<br>
<br>
If you look at the edges on the horizontal axis, you do not get as
weird an activity distribution as near the edges on the vertical
axis.<br>
I suppose this is due to the fact that your reconstructed image is
smaller in the vertical axis compared to the horizontal axis.<br>
<br>
As you suggested:<br>
<br>
(1) When you will correct for attenuation, all this "noise" around
the phantom will be much lower as the signal from the phantom will
be increased much higher than outside the phantom.<br>
<br>
(2) Very low statistics can also contribute to weird signal.<br>
<br>
But:<br>
<br>
(3) Are you reconstructing data that contain scatter and random
coincidences without correcting for them ?<br>
In this case, these accidental coincidences may fakely originate
from around the phantom, so if you truncate your image too much,
then this fake signal may belong to the exterior of the image, so
that it will accumulate near the edges of your image. That is
normal and this may explain what you get.<br>
<br>
As a first suggestion, you should reconstruct an image with the
same X and Y dimensions, large enough to include all the signal,
including accidental coincidences.<br>
<br>
I hope it helps.<br>
<br>
Best<br>
Simon<br>
<br>
Le 05/09/2018 à 14:29, Daiki HAYAKAWA a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:6127DB2C-5341-44B0-80B0-0BDD59A07972@unige.ch">
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Hi Simon et al,<br class="">
<br class="">
Thank you for your kind response (and sorry for my late reply).<br
class="">
<br class="">
We probably performed reconstruction with proper LUT file.<br
class="">
I would like to ask the very low sensitivity on the edges in the
sensitivity map(*1). The edges would create weird distributions on
the edges in the reconstructed image(*2). <br class="">
How can we solve this issue? Please note that we don’t have enough
statistics and we haven’t applied normalization/attenuation yet.<br
class="">
<br class="">
Thank you again and best regards,<br class="">
Daiki Hayakawa
<div class=""><br class="">
</div>
<div class="">(*1) sensitivity map</div>
<div class=""><img apple-inline="yes"
id="1E7E4770-956D-4595-9471-D8BFB07ECDC2"
src="cid:part1.BB6A7610.F98ADF05@cea.fr" class=""><br class="">
<div><br class="">
</div>
<div>(*2) reconstructed image (Derenzo phantom)</div>
<div><img apple-inline="yes"
id="0CD81357-6BE0-4BFE-A96E-CD675B3B1C00"
src="cid:part2.D1358F3B.67144F7B@cea.fr" class=""></div>
<div><br class="">
<blockquote type="cite" class="">
<div class="">On Jul 25, 2018, at 18:04, Simon Stute <<a
href="mailto:simon.stute@cea.fr" class=""
moz-do-not-send="true">simon.stute@cea.fr</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div text="#000000" bgcolor="#FFFFFF" class="">
<div class="moz-cite-prefix">Hi,<br class="">
<br class="">
Yes, the order as (*2) is assumed: <span class="Apple-tab-span" style="white-space:pre">
</span>castorID = iDet + iRing*NDet + iLayer*NRing*NDet;<br class="">
<br class="">
This ordering is only used to get the crystal
dimensions as specified per layer in the header file
of the scanner description (to compute the correct
depth position in the crystal).<br class="">
So that if the crystal IDs you write in the datafile
to be reconstructed are in agreement with the order of
the crystal positions you wrote in the LUT file, the
reconstruction should be fine.<br class="">
<br class="">
As you get a correct sensitivity map, this means that
IDs written in the datafile are likely not correct.<br
class="">
<br class="">
Also to be sure, here in your email, I assume that
NDet is the number of detectors inside a single ring,
not for all the layer. Whereas in the header of the
LUT file, this is the total number of crystals per
layer which should be provided.<br class="">
<br class="">
Best<br class="">
Simon<br class="">
<br class="">
<br class="">
Le 25/07/2018 à 16:58, Daiki HAYAKAWA a écrit :<br
class="">
</div>
<blockquote type="cite"
cite="mid:0EFB48AF-501A-46B6-A43A-5DA70C6F4997@unige.ch"
class="">
Dear CASToR users, <br class="">
<br class="">
We are trying to reconstruct PET image from a binary
LUT file following the page 21 in the general
document. The sensitivity map looks fine
but reconstructed images make no sense. We think that
there would be a problem regarding to castor ID for
each detector (but we are not fully sure).<br class="">
We currently create a binary LUT file as the for loops
(*1) suggested in the document. Does the castor ID for
detectors follow the order like (*2)?<br class="">
<br class="">
Any suggestions/comments are welcome.<br class="">
<br class="">
Thank you and kind regrads,<br class="">
Daiki Hayakawa<br class="">
<br class="">
<br class="">
(*1)<br class="">
for(iLayer=0;iLayer<NLayer;iLayer++)<br class="">
for(iRing=0;iRing<NRing;iRing++) <br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>for(iDet=0;iDet<NDet;iDet++)
{ <br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&Posx[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr); <br
class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&Posy[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr);<br
class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&Posz[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr);<br
class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&OrVx[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr);<br
class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&OrVy[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr); <br
class="">
<span class="Apple-tab-span" style="white-space:pre"></span>fwrite(&OrVz[iLayer][iRing][iDet],sizeof(FLTNBLUT),1,fPtr); <br
class="">
} <br class="">
<br class="">
(*2)<br class="">
for(iLayer=0;iLayer<NLayer;iLayer++)<br class="">
for(iRing=0;iRing<NRing;iRing++) <br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>for(iDet=0;iDet<NDet;iDet++)
{ <br class="">
<span class="Apple-tab-span" style="white-space:pre"></span>castorID
= iDet + iRing*NDet + l*NRing*NDet;<br class="">
}<br class="">
<br class="">
<div class="">
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class="">
<div style="word-wrap: break-word;
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Daiki HAYAKAWA</div>
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Group: TT-PET</div>
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<div style="word-wrap: break-word;
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class="">
DPNC, University of Geneva</div>
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class="">
E-mail: <a
href="mailto:daiki.hayakawa@cern.ch"
class="" moz-do-not-send="true">daiki.hayakawa@cern.ch</a> ,
<a href="mailto:Daiki.Hayakawa@unige.ch"
class="" moz-do-not-send="true">Daiki.Hayakawa@unige.ch</a></div>
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