[gate-users] Image Reconstruction of Gate DST output

[Mutanga Theodore]

Hi Kris, thanks for the mail,
I used the default params for the Ray Tracing and I am at least getting
some results ( images). What is the range of the number of rays ? What
about bin normalization ? do I need all that , given that I am only
interested in reconstructing the images for three point sources and
measuring the resolution.

cheers
Theo
> Hi Theo
>
> I don't think you're running the debug executables, as normally there
> should be line information in the 'info stack'. You could do a 'list' to
> see the lines around where the crash occurred. If gdb says 'no line
> info' or something, you're sure you're running the wrong executable.
> Finally, if you were running the debug version, the program would have
> stopped with an assert().
>
> However, I've found out what happens. I forgot about the fact that at
> present the interpolating backprojector cannot handle DST data because
> its number of views is not a multiple of 4. This is because this data
> has less symmetries. This might not be too difficult to fix, but at
> present your only choice is to use the backprojector using the ray
> tracing matrix. For OSMAPOSL/sensitivity this is discussed in the STIR
> manual. For FBP and 3DRP I'm not so sure what's going to happen
> (normalisations will be wrong etc.) You should get a decent looking
> image, but especially in the case of 3DRP, somebody will have to think
> about normalisations between segments.
>
> You can try this as follows
> -----------------
> ; usual FBP2D/3DRP parameters
>
> Back projector type:= matrix
> Back Projector Using Matrix Parameters:=
>   matrix type:= ray tracing
>   ; usual parameters for ray tracing matrix
>   ; you probably want to increase the number of rays used
>
> End Back Projector Using Matrix Parameters:=
>
> ; some more of the usual FBP2D/3DRP parameters
> -----------------
>
> Again, for FBP2D this probably gives you an incorrect global scale
> factor, while for 3DRP quantification is probably more drastically
> screwed up. OSMAPOSL will work just fine.
>
> Kris
>
>
>> -----Original Message-----
>> From: gate-users-bounces at lphe1pet1.epfl.ch
>> [mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of
>> Mutanga Theodore
>> Sent: 05 January 2005 22:06
>> To: GATE feedback and helpline for Users
>> Subject: RE: [gate-users] Image Reconstruction of Gate output
>>
>>
>> Hi Kris ,
>> these are the outputs from running FBP3DRP in debug mode
>>
>> (gdb) r FBP3DRP.par
>> Starting program:
>> /afs/hpc2n.umu.se/home/m/muathe02/bin/FBP3DRP FBP3DRP.par
>>
>> WARNING: Scanner GE Discovery ST: transaxial bucket info is not set
>>
>> WARNING: Scanner GE Discovery ST: axial bucket info is not set
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x00000000004342de in
>> stir::BackProjectorByBinUsingInterpolation::actual_back_project ()
>>
>> (gdb) info stack
>> #0  0x00000000004342de in
>> stir::BackProjectorByBinUsingInterpolation::actual_back_projec
>> t () #1  0x0000000000512ec8 in
>> stir::BackProjectorByBin::back_project () #2
>> 0x0000000000512cf8 in stir::BackProjectorByBin::back_project
>> () #3  0x00000000005298a6 in
>> stir::FBP2DReconstruction::reconstruct () #4
>> 0x000000000048dd72 in
>> stir::FBP3DRPReconstruction::do_2D_reconstruction () #5
>> 0x000000000048d4f2 in
>> stir::FBP3DRPReconstruction::reconstruct () #6
>> 0x0000000000514178 in stir::Reconstruction::reconstruct () #7
>>  0x000000000048d109 in
>> stir::FBP3DRPReconstruction::reconstruct () #8
>> 0x00000000004069eb in main ()
>> (gdb)
>>
>> Could you get a clue about the problem from these lines ?
>>
>
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