[Gate-users] Re : Re : Re : SPECT intrinsic spatial resolution

[Samuel BURG]

about your sample image, yes we see the collimator holes on it.

I think there should be something wrong in your script.

can you :

1) try a simulation with a huge spResolution, like 37.0 mm ?

2) send by e-mail the full gate macro you use, so we can check it ?

best regards,

-----------------------------------------------------------
Samuel Burg


Mail : <samuel_burg at yahoo.fr>
-----------------------------------------------------------
"Aw, come on, who would be so stupid as to insert a cast
to make an error go away without actually fixing the error?"
Apparently everyone. 
-- Raymond Chen --
-----------------------------------------------------------




________________________________
De : "Rajaram, Ramya (H USA)" <ramya.rajaram at siemens.com>
À : Samuel BURG <samuel_burg at yahoo.fr>
Envoyé le : Jeu 16 septembre 2010, 21h 00min 59s
Objet : RE: Re : [Gate-users] Re :  SPECT intrinsic spatial resolution

Samuel,

I have also tried 1024x projection images with pixels of either 0.3 or 0.6 mm 
and in fact that is when I started getting the suspicion of whether the 
intrinsic is getting convolved because at such small pixel sizes, my projection 
images don't look smooth at all - it is almost as if I can see the individual 
collimator holes. I am attaching the image here so you can see what I mean.  
This image was also obtained by simulating a point source at ~10 cm from 
collimator face with 3.7 mm intrinsic resolution. I can't understand this at all 
:-(

Thank you so much for your time and help,

Ramya

-----Original Message-----
From: Samuel BURG [mailto:samuel_burg at yahoo.fr] 
Sent: Thursday, September 16, 2010 1:48 PM
To: Rajaram, Ramya (H USA); gate-users at lists.opengatecollaboration.org
Subject: Re : [Gate-users] Re : SPECT intrinsic spatial resolution

ok,

you don't see any difference between you simulation with spResolution 0.0 and 
3.2mm, because your pixel size and the effect of your collimator is much more 
higher than your spResolution.

if you want to asses anything with a spResolution about Xmm, your pixel has to 
be at least X/3mm (strict minimum) or less, or you won't see a lot about your 
spResolution.

regards,

-----------------------------------------------------------
Samuel Burg


Mail : <samuel_burg at yahoo.fr>
-----------------------------------------------------------
"Aw, come on, who would be so stupid as to insert a cast
to make an error go away without actually fixing the error?"
Apparently everyone. 
-- Raymond Chen --
-----------------------------------------------------------


________________________________

De : "Rajaram, Ramya (H USA)" <ramya.rajaram at siemens.com>
À : gate-users at lists.opengatecollaboration.org
Envoyé le : Jeu 16 septembre 2010, 19h 15min 19s
Objet : Re: [Gate-users] Re : SPECT intrinsic spatial resolution

I am simulating planar image of a point source, so there is no phantom. Also, I 
have put in only the collimator and the continuous crystal detector - no back 
compartment or any other layers. I output the projection images using the the 
following code:

/gate/output/projection/enable
/gate/output/projection/setFileName file6
/gate/output/projection/pixelSizeX 2.4 mm
/gate/output/projection/pixelSizeY 2.4 mm
/gate/output/projection/pixelNumberX 256
/gate/output/projection/pixelNumberY 256

Thanks,

Ramya




-----Original Message-----
From: Samuel BURG [mailto:samuel_burg at yahoo.fr] 
Sent: Thursday, September 16, 2010 10:35 AM
To: Rajaram, Ramya (H USA); gate-users at lists.opengatecollaboration.org
Subject: Re : [Gate-users] SPECT intrinsic spatial resolution

Yes, GATE do apply a spatial blurring in your projection when using 
/gate/digitizer/Singles/spblurring/setSpresolution

but to help you, we need your full macro file.
also remember that the collimator, phantom scattering and the background 
compartment of the PMT play a lot in sp resolution.

-----------------------------------------------------------
Samuel Burg


Mail : <samuel_burg at yahoo.fr>
-----------------------------------------------------------
"Aw, come on, who would be so stupid as to insert a cast
to make an error go away without actually fixing the error?"
Apparently everyone. 
-- Raymond Chen --
-----------------------------------------------------------


________________________________

De : "Rajaram, Ramya (H USA)" <ramya.rajaram at siemens.com>
À : gate-users at lists.opengatecollaboration.org
Envoyé le : Jeu 16 septembre 2010, 16h 59min 48s
Objet : [Gate-users] SPECT intrinsic spatial resolution

Dear Gaters,

Does GATE really convolve the intrinsic spatial resolution for SPECT? I
have generated 256x256 projection images from two macros, both identical
except for the fact that in one, the spResolution is set to 3.7 mm, in
the other it is set to 0 mm and yet, the two images look identical. A
simple profile also gives me the same system resolution for both - leads
me to think the spResolution is somehow not being convolved -- could
someone please explain/help?

The following code is what I used to set the digitizer up:

/gate/digitizer/Singles/insert adder
/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setResolution 0.09
/gate/digitizer/Singles/blurring/setEnergyOfReference 140. keV
/gate/digitizer/Singles/insert spblurring
/gate/digitizer/Singles/spblurring/setSpresolution 0. mm (3.7 mm)
/gate/digitizer/Singles/spblurring/verbose 2
/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 50. keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 200. keV

Thank you very much,

Ramya

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