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<p>Hi,</p>
<p>By default, for list-mode data, the sensitivity image is
generated by projecting all available lines of response. This
process is indeed dependent on the number of detectors. The PET
list-mode benchmark uses a system with ~20k detectors and a
normalization datafile to generate the sensitivity image. In this
case, the processing time depends on the number of data channels
in the normalization datafile, which also depends on the number of
detectors, so it still takes some time to process.</p>
<p>Several remarks:<br>
</p>
<p>- Make sure that all parallel computing were enabled when you
compiled the code: CASTOR_OMP and CASTOR_MPI (if you use a
cluster of machine compatible with MPI) variables must be set to 1
. <br>
When using castor-recon, set -th 0 to enable multithreading.<br>
</p>
<p>- If you know the minimum transaxial angle between two detectors
required to form a line a response, you could reduce the computing
time by setting the following variable in the geometry file of
your scanner (*.geom file in <i>/config/scanner</i>):<br>
min angle difference : x <br>
(x being the angle in degree).</p>
<p>This should moderately reduce the computing time as by default,
the code blindly projects all lines of response without first
checking if they will cross the FOV or not. With this option, the
lines of response drawn by detectors whose transaxial angle is
below this value will be ignored.<br>
</p>
<p>- It should be possible (though not necessarily trivial) to
analytically compute a sensitivity image for most systems. You
could bypass the sensitivity image computation by providing the <i>castor-recon</i>
executable with such image in interfile format with the option <i>-sens
path/to/analytic/sens/image.hdr</i><br>
Note that this image should take account of attenuation in the
object as well as calibration factor.</p>
<p>Hope this helps!<br>
Thibaut</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 26/08/2019 21:20, Sveta wrote:<br>
</div>
<blockquote type="cite"
cite="mid:E56DF612-E51B-404B-8A4F-59CEEBD0A416@txcorp.com">
<pre class="moz-quote-pre" wrap="">Hi,
We are currently using castor to reconstruct images from GATE Simulation, the process of running castor-GATEMacToGeom and castor-GATERootToCastor is going quite well. However when running castor-recon the generation of the sensitivity image is extremely slow. A simplified version of our problem (~28672 elements) takes 16 minutes to process through this step. We would like to full simulations with nearly 10 times as many elements.
Our question is, is the sensitivity image generation time purely driven by the number of elements? Is there any way to decrease the setup time, available benchmarks were done with it nearly instantaneous.
Any suggestions for us?
Thank you,
Sveta and Peter
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<pre class="moz-signature" cols="72">--
Thibaut MERLIN -- PhD
Docteur en Imagerie Médicale au Laboratoire de Traitement de l'Information Medicale (LaTIM - INSERM UMR 1101)
Institut Brestois de recherche en Bio-Santé (IBRBS)
12 Avenue Foch, 29200 Brest, FRANCE
Tel: 06.75.12.24.90</pre>
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