[gate-users] Image Reconstruction of Gate DST output

[Kris Thielemans]

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 ?
>