<div dir="ltr"><span style="font-size:12.8px">Hello Simon,</span><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Thank you for your replies to my two emails.</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">I've attached a file of a CASToR-formatted crystal lookup table for an arbitrary PET scanner called "aSamplePETScanner.lut" with its header "aSamplePETScanner.hscan". Let's assume that I'd like to visualize a sample line of the system matrix that corresponds to a coincidence between crystalIDs 6000 and 6142. The XYZ coordinates of the centroids of the crystals, as defined by CASToR's coordinates system, are [-161.4 -11.0 -15.8] and [156.4 37.4 -12.6]. I've made a sample binary coincidence data file that has the information of this coincidence and set the time of the event to 1 ms. This file is called "aSampleLOR.Cdf" and is attached along with its header "aSampleLOR.Cdh". No attenuation/scatter/random/<wbr>normalization coefficient is defined in this overly simplified case.</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">I usually find visualizing a single row of the system matrix extremely helpful if I want to learn the effects of various reconstructions parameters on image quality. Today in my investigations, I learned that it actually is possible to see this coincidence only if <b>no convolution</b> is used. I've attached a 2D superimposed image of all image slices for the mentioned event to this email. Once I introduce a convolution (i.e. -conv ...... ), the images turn to be blank. So, I'm wondering how one can have the images of a single coincidence with some convolution parameters introduced. </div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Also, here are some side notes about what I observed about this discussion. They may be useful for other CASToR users too, if you use one or only a few coincidences:</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">- You probably see uniform images in iteration 1 and 2 and see your LOR(s) only after the 2nd iteration which puzzles me a bit,</div><div style="font-size:12.8px">- Enabling multi-threading when only a few events are used directs the reconstruction code to an infinite loop.</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Thank you,</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">Cheers,</div><div style="font-size:12.8px">Reza</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, May 2, 2017 at 10:47 AM, Simon Stute <span dir="ltr"><<a href="mailto:simon.stute@cea.fr" target="_blank">simon.stute@cea.fr</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div class="m_-254298814998127560moz-cite-prefix">Hi again !<br>
<br>
Could you send the geometry description of your scanner along with
your tiny list-mode please ?<br>
I will be able to test it quickly and find why you do not see
nothing.<br>
<br>
Cheers<br>
Simon<div><div class="h5"><br>
<br>
Le 28/04/2017 à 19:06, M.R Teimoori a écrit :<br>
</div></div></div>
<blockquote type="cite"><div><div class="h5">
<div dir="ltr">Hi All,
<div><br>
</div>
<div>I would like to visualize a sample line of the system
matrix using CASToR. If I am not wrong, this should be
feasible when you input a single coincidence data
(corresponding to the desire line of the system matrix) and
reconstruct an image using listmode EM with 1 iteration.
However, CASToR returns a uniform image if the input has only
the data for one coincidence. Why is this not possible? If
anybody knows a workaround, please let me know.</div>
<div><br>
</div>
<div>Thank you for your help,</div>
<div><br>
</div>
<div>Cheers,</div>
<div>Reza</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
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