[gate-users] Image Reconstruction of Gate output

[Mutanga Theodore]

HI Kris,

I don't know if this is more a STIR issue but it concerns reconstruction
from GATE cylindrical PET system using the codes from Sadek.

I have modified the codes replacing DLS things with DST things and then I
used creat_projdata template to generate a header file. Using
manip_prodata, I can view the sinograms, but when I try to use any of the
reconstruction tools, (FBP2D , FBP3DRP , OSMAPSL ) I get a segmentation
fault, can you help me trace the source of the problem ?

here's a sample of the header file :

!matrix size [4] := 15
matrix axis label [3] := view
!matrix size [3] := 210
matrix axis label [2] := axial coordinate
!matrix size [2] := { 7,13,19,25,31,37,43,47,43,37,31,25,19,13,7}
matrix axis label [1] := tangential coordinate
!matrix size [1] := 223
minimum ring difference per segment := {
-22,-19,-16,-13,-10,-7,-4,-1,2,5,8,11,14,17,20}
maximum ring difference per segment := {
-20,-17,-14,-11,-8,-5,-2,1,4,7,10,13,16,19,22}
number of rings := 24
number of detectors per ring := 420
*****************

and here is a definition of the number of slices per segment.

 int num_segments;
  int num_slices_per_segment[8] = {47,43,37,31,25,19,13,7};  //Number of
projection planes per $

projections.hs ( header ) points to projections.stir which was generated
using Sadeks code with DST modifications by me.

------------------------------


WARNING: Scanner GE Discovery ST: transaxial bucket info is not set

WARNING: Scanner GE Discovery ST: axial bucket info is not set
Segmentation fault
-------------------------

Is there a way to go ahead without this error ?

Cheers

Theodore



>> BTW, I was pussled by the sinogram width of DST (420 crystal
>> per ring). The number 249 is larger than the 420/2 = 210. How
>> can DST get the extra LORs of 39? By interpolation? Could
>> this help to improve the spatial resolution? Thank you!
>>
> Notation: N= num_detectors per ring
>
> Why do you think that the max sinogram width is N /2? This is a hardware
> choice (recent CTI scanners tend to have sinogram_width=N/2). The
> 'physical' maximum of LORs in 2D sinograms is (N^2-N)/2 (i.e. all lines
> between pairs of detectors, excluding the degenerate cases, and
> identifying det pairs ij and ji). The max number of views is N/2 (you'd
> expect N, but it's halved because of interleaving). So, the max sinogram
> width is something like (N-1)
>
>
> Kris
>
> _______________________________________________
> gate-users mailing list
> gate-users at lphe1pet1.epfl.ch
> http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users
>