[Gate-users] How is the raw sinogram data organized [288, 288, 1024]?

[Arda Konik]

Hi,
How is the raw sinogram data organized ? That is, for which values of   
Z  the 2D sinograms are direct and oblique in [ 288,288, Z ] and how  
can I find Z values in terms of ring difference and axial position?
The explanation in the user manual is not clear to me. In an earlier  
email (copied here) I tried to explain this organization for 4 rings  
but the rules/pattern doesn't seem to apply for 32 rings
I will be glad if someone could clarify this for a 32 ring (or better  
n -ring) ECAT scanner
Thanks,

arda konik




On Dec 18, 2008, at 2:30 AM, Arda Konik wrote:

> Hi,
> I believe I have the answer for this question that i asked a week  
> ago. I first reduced the problem to 4 rings (i.e.  , setting  "  / 
> gate/crystal/cubicArray/setRepeatNumberZ 1 " instead of 8 which  
> corresponds to the 32-ring scanner) and 16 2D-sinograms. Then, i ran  
> several short simulations placing spherical sources (one  or 2  
> sources per simulation) at different locations in a cylindrical  
> water phantom. For each simulation, out of 16 possible sinograms  
> only 2 (for 1 source) or 4 (2 sources) sinograms appeared in the  
> output data which seems reasonable (at least to me) when you draw  
> the scanner and guess the ring pairs to create those sinograms. As a  
> conclusion i found that
> the data is organized as below, where "rd" is the ring difference.
> { rd=0, rd = 1, rd= -1 , rd = 2, rd= -2, rd = 3, rd= - 3 } or
> more explicity in terms of ring numbers :
> { (1,1),(2,2),(3,3),(4,4),  (1,2),(2,3),(3,4),(2,1),(3,2),(4,3),    
> (1,3),(2,4), (3,1),(2,4),   (3,4), (4,3) }
> as you can see there are 16 ring pairs.
> I am assuming for large ring numbers this organization will be in  
> similar fashion.
> To visualize these slices i used Osirix (image processing, freeware)  
> on a Mac OS.
> http://www.apple.com/downloads/macosx/imaging_3d/osirix.html
>
> i hope this will be helpful for some users
> cheers,
>
> arda konik
> University of Iowa
>
>
> On Dec 10, 2008, at 2:23 PM, Arda Konik wrote:
>
>> Hi,
>>
>> Could anyone explain the organization of sinogram output from  "  
>> PET_Ecat_System.mac " example, please?
>> A 32 ring system generates 1024 2D sinograms, and they must be  
>> indexed by ring difference ( Ri - Rj) and axial position (Ri + Rj)/ 
>> 2 according to the info file and the Gate manual. However, i  
>> couldn't even figure out which ones are direct sinograms ( Ri - Rj  
>> =0) out of these 1024 sinograms.
>>
>> I tried to understand the organization by simulating the  
>> acquisition from sources at different locations and shapes;  
>> decreasing ring number but still couldn't solve this except that i  
>> can see a pattern due to ring difference indexing, when i plot the  
>> total counts of the sinograms...What other approach would you  
>> recommend to figure out the data organization?
>>
>> Thanks,
>> arda konik
>> University of Iowa
>> <ATT00001.txt>
>
> <ATT00001.txt>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20090707/66120c05/attachment.htm>