[Castor-users] attenuation correction in CASToR TOF recon image

[赵鑫]

Dear CASToR developers and users,

    We simulated a cylindrical phantom using GATE and extract time and crystalID information from ROOT file. We organized two groups of Cdh&Cdf files followed CASToR input datafile format, for non-TOF and TOF reconstruction respectively. Two recon images are shown in "non-TOF recon.png" & "141ps TOF recon.png" images as presented in the attachment. But I found out that there is almost no attenuation that can be seen in the "141ps TOF recon.png" image compared to "non-TOF recon.png". From the image profiles in "profile.png", it can be seen from the non-TOF recon image that the central area has obvious count attenuation, while the TOF recon image shows no sign of attenuation. I am curious about why because I applied no additional "-atn XXXX.hdr" attenuation correction when running castor-recon for TOF reconstruction. 
    The CASToR recon command of 141ps TOF recon is: "castor-recon -df /home/castor/BrainPET_IEC_F18_3sphere1_5p3c_TOF141p42ps.Cdh -opti MLEM -it 10:9 -proj joseph -conv gaussian,1.7,1.7,3::psf  -dim 630,630,250  -vox 0.3225,0.32255,0.3225   -dout /home/castor/img/BrainPET_IEC_F18_3sphere1_37and22and13_5p3concent_510s_TOF141p42ps_20220605 -th 0". The TOF recon datafile  header "BrainPET_IEC_F18_3sphere1_5p3c_TOF141p42ps.Cdh" is also submitted in the attechment.
    Do you have any idea why attenuation seems not obvious in the TOF recon image from castor-recon?  Can you point out what went wrong with my TOF Recon? Any advice and suggestion will be greatly appreciated. Thank you! 

All the best,
Xin Zhao

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