[Gate-users] Image Reconstruction by MLEM

Yanchao Huang huangycsmu at gmail.com
Tue Jan 1 04:14:11 CET 2019

Dear Gate users,
Recently, I simulated a small animal PET scanner by GATE 8.0. The scanner
consists of 60 block-detectors in 5 contiguous rings. Each detector
consists of 13X13 LYSO crystals and  each pixel size is 1.8X1.8X15 mm.
Firstly,an uniform cylindrical source was simulated and the list-mode data
in ASCII format  was acquired.
Secondly, I reorganized the data onto histgram. Then SSRB was applied to
gain a 2-D data set. Thirdly, I applied the 2-D ray tracing algorithm to
generate the system matrix simply. Each line of response(LOR) was connected
with the center of each crystal. And the intersection length of the image
pixel and the LOR was considered as the detected probability. However, a
high-light artifact showed in the MLEM reconstructed image.
I think this error may come from the sensitivity map which also shows a
spider-web shape distribution due to the scanner geometric structure. But I
don't know how to deal with it. Does any one has ever meet such case? I‘m
very much looking for your help and suggestions.
By the way, Happy New Year to your all!
Best wishes!
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