[gate-users] sample image from my IQ_phantom simulation

[Schmidtlein, Ross/Sloan-Kettering Institute]

Hi Theodore,

Complex phantoms like the IQ phantom may require you to modify the STIR
image_generation software.  In it's standard form STIR can generate
ellipsoids and ellipsoidal cylinders.  I have modified some of this code
to produce sectors of cylinders and boxes.  I have given these
modifications to Kris but they have not been implemented in a STIR
release yet.  I am hoping that they are clean enough that he can
implement them in the next release with out too much fuss.  These
modifications should work just as well for a voxel phantoms but may be
quite tedious to build.  For voxelized phantoms look at the STIR
software and then see if you can translate the GATE voxel matrices into
a STIR image it should be very straight forward.  STIR is written
cleanly enough that the output from the image_generation routine is easy
to follow.

We are replicating and old DLS experiment with the IQ phantom and we
have about 2E7 events at this point and the run times are huge.  We have
8 processors that we have been building this on and it is still weeks of
computer time.

I'm away from my research desk for a bit but I'll send you some of *.par
and *.mac files we have so that we can compare our simulation and
reconstruction steps.

ross

-----Original Message-----
From: gate-users-bounces at lphe1pet1.epfl.ch
[mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of Mutanga
Theodore
Sent: Friday, September 16, 2005 3:51 AM
To: GATE feedback and helpline for Users
Subject: RE: [gate-users] sample image from my IQ_phantom simulation

Hi Ross
thanks for the hints

> Hi Theodore,
>
> Attenuation correction can be done via STIR by building an attenuation

> coefficient image and then using the projection data correction 
> routine to scale the data properly.
What if my phantom is complex like the IQ phantom I designed that from
previous macros from you I suppose,(maybe we should check and see if it
is alright, i'll attach a copy of that macro to you) of what if Im using
voxel phantoms how can I use stir to build this attenuation image ? or
will CT image data of the phantom do ?
That's probably the most straight forward
> method.  Also, arc correction is important in order to avoid object

Can we do arc correction with the new version of stir (test2 1.4?) Have
you done that with stir ?
> distortions for this phantom.
>
> I have been doing a similar reconstruction with the DLS and have been 
> unsure about the counting statistics with respect to the contrast 
> ratios.  How many coincidences do you have in your image data? Im
generating about 10^6 coincidences but the warm sphere is completely
lost. If you dont mind ill like to know how your source distribution
looks like int the macros. The computation time is astronomical with
increased activity for the sources! If I didn't have the cluster I won't
be able to manage.

cheers

>
> Cheers,
>
> ross
>
> -----Original Message-----
> From: gate-users-bounces at lphe1pet1.epfl.ch
> [mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of Mutanga 
> Theodore
> Sent: Thursday, September 15, 2005 7:20 AM
> To: gate-users at lphe1pet1.epfl.ch
> Subject: [gate-users] sample image from my IQ_phantom simulation
>
> I will like to present an image that I obtained using a simulation of 
> the Discovery St and reconstruction with stir for the iq-phantom, some

> spheres are missing and there is heavy attenuation , I am currently 
> exploring ways of simulating and correcting for attenuation with GATe 
> and STIR, any suggestions?
>
>
>
>
>
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>


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