<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div>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</div><div>the data is organized as below, where "rd" is the ring difference.</div><div>{ rd=0, rd = 1, rd= -1 , rd = 2, rd= -2, rd = 3, rd= - 3 } or </div><div>more explicity in terms of ring numbers :</div><div>{ (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) } </div><div>as you can see there are 16 ring pairs.</div><div>I am assuming for large ring numbers this organization will be in similar fashion.</div><div>To visualize these slices i used Osirix (image processing, freeware) on a Mac OS.</div><div><a href="http://www.apple.com/downloads/macosx/imaging_3d/osirix.html">http://www.apple.com/downloads/macosx/imaging_3d/osirix.html</a></div><div><br></div><div>i hope this will be helpful for some users</div><div>cheers,</div><div><br></div><div>arda konik</div><div>University of Iowa</div><div><br></div><div><br></div><div><div><div>On Dec 10, 2008, at 2:23 PM, Arda Konik wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div><br></div><div>Could anyone explain the organization of sinogram output from " <span class="Apple-style-span" style="font-family: 'Lucida Grande'; ">PET_Ecat_System.mac " example, please? </span></div><div><span class="Apple-style-span" style="font-family: 'Lucida Grande'; ">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. </span></div><div><font class="Apple-style-span" face="'Lucida Grande'"><br></font></div><div><font class="Apple-style-span" face="'Lucida Grande'">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?</font></div><div><font class="Apple-style-span" face="'Lucida Grande'"><br></font></div><div><font class="Apple-style-span" face="'Lucida Grande'">Thanks,</font></div><div><font class="Apple-style-span" face="'Lucida Grande'">arda konik</font></div><div><font class="Apple-style-span" face="'Lucida Grande'">University of Iowa</font></div><span><ATT00001.txt></span></div></blockquote></div><br></div></body></html>