[Castor-users] Loss of TOF precision after converting ROOT to TXT

[Zipai Wang]

Dear CASToR developers and users

I am post-processing the root list-mode data generated from the GATE
simulation and reconstructing it using the CASToR. First I convert the ROOT
to TXT, after the post-processing, I convert the TXT back to ROOT for the
reconstruction. Most of the things went well, and the image can be
successfully reconstructed by CASToR.

However, recently I am trying to add TOF in the recon, but soon realize
that the txt file converted from ROOT has a lower TOF data precision. I
have output the .dat file from GATE directly for a comparison: For example,
In the txt file converted from ROOT, I got TOF = 4.83994e-06 for eventID
30. In .dat, I got  TOF = 4.83994034373751110439431e-06 for the same event.

The loss of precision basically ruined the image since every event got the
same time difference. Although I can bypass the loss of precision during
the root to txt by using the .dat files, I am worrying that the same thing
will happen again when I convert txt back to ROOT.

Apologize that I am very new to c programming and ROOT. I attached the
converting code I am currently using. May someone point out where is the
problem, please. Thank you very much for your attention, appreciate it!



Cheers!
-- 
Zipai Wang
Biomedical Engineering PhD student
Stony Brook University
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