attenuation correction in CASToR TOF recon image

General Discussions
1

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

141ps TOF recon.jpg
141ps TOF recon.jpg1920×895 179 KB

non-TOF recon.jpg
non-TOF recon.jpg1920×885 139 KB

profile.jpg
profile.jpg1905×895 293 KB

BrainPET_IEC_F18_3sphere1_5p3c_TOF141p42ps.Cdh (396 Bytes)

2

Hello all,
I hope you are well.
I am actually preparing my final project of the year, is about Modeling and simulation of PET Scan with GATE.
I chose “Ge STE PET/CT Scan” as a model but I still have a problem.
I don’t understand how I will evaluate my simulation, what parameters should I calculate to say that my simulation is correct?

Thanks in advance.
Cordially.

4

Dear Xin Zhao,

Indeed the output you get is strange, but I don’t see anything wrong in your datafile header or command line options.

Do you get the same output (no attenuation) when you try to reconstruct the tof dataset without tof (i.e delete the tof related line in the datafile header) ? Did you try to reconstruct with different time resolution to check if this has an impact on the observed attenuation ?

Best,
Thibaut

5

Hi, you can evaluate the recon image from your simulation by calculated system sensitivity, NECR, SNR… and compare the calculated results with your expected values or the reported values in the papers of those familiar PET system.

6

Thank you a lot for your reply! I am still focusing on getting the correct TOF reconstruction images using GATE simulation data. Maybe later I can share the TOF recon results from CASToR. CASToR is really easy to use, which greatly helps our team’s research work. The new discourse forum is a great job!

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