TR: [Gate-users] Question about sinograms

[COMTAT Claude]

Actually, they are N_cryst angles of view, and N_cryst/2 radials bin per angle of view (that is, N_crystal²/2 LORs). BUT, the location of the sinogram radial bins for the even angle views is shifted by half the bin size relative to the odd angle views (just do the drawing of your detector ring, and you will see it).

 

Let's assume you have 12 crystals. The sinogram sampling for the 12²/2=72 LORs will look like:

 

 

View

0          x                      x                      x                      x                      x                      x                      

1                      x                      x                      x                      x                      x                      x

2          x                      x                      x                      x                      x                      x

3                      x                      x                      x                      x                      x                      x

4          x                      x                      x                      x                      x                      x                      

5                      x                      x                      x                      x                      x                      x

6          x                      x                      x                      x                      x                      x

7                      x                      x                      x                      x                      x                      x

8          x                      x                      x                      x                      x                      x

9                      x                      x                      x                      x                      x                      x

10        x                      x                      x                      x                      x                      x

11                    x                      x                      x                      x                      x                      x

                                                           Radial bin

 

In order to get a regular rectangular sinogram sampling for the 72 LORs, usually two consecutive sinogram rows are merged together:

 

View

0          x          x          x          x          x          x          x          x          x          x          x          x  

1          x          x          x          x          x          x          x          x          x          x          x          x  

2          x          x          x          x          x          x          x          x          x          x          x          x  

3          x          x          x          x          x          x          x          x          x          x          x          x  

4          x          x          x          x          x          x          x          x          x          x          x          x  

5          x          x          x          x          x          x          x          x          x          x          x          x

                                                           Radial bin

Resulting in a N_cryst/2 view angles and N_cryst radial bins sinogram. This is exactly what is done in Gate.

 

Hope this help,

 

Claude

________________________________

De : gate-users-bounces at lists.healthgrid.org [mailto:gate-users-bounces at lists.healthgrid.org] De la part de Su, Yi
Envoyé : lundi 7 janvier 2008 23:34
À : 'gate-users at lists.healthgrid.org'
Objet : [Gate-users] Question about sinograms

 

Hi all,

 

I am a little bit confused about the terminology used in User's Guide describing the sinogram output. For 2D sinograms, there are a maximum of N_cryst radial bins and N_cryst/2 azimuthal bins. I assume this means there are N_cryst/2 angle of views, and in each view there are a maximum of N_cryst bins. Am I right? How are the bins generated if radial bins are specified to be smaller than N_cryst? Any information would be appreciated. Thanks a lot.

 

Yi 

 

 

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