How to apply 'time resolution (200 ps)' and 'random&scatter correction' to the offset detector

General Discussions
1

Dear CASToR Users and Developers,

Hi I am Suhwan Kim

I designed the offset detector of ‘PETscanner’ using the GATE tool.

I want to apply ‘time resolution (200 ps)’ and ‘random&scatter correction’ when performing image reconstruction.

I don’t know how to proceed.

can you help me??

Thanks

Suhwan Kim

2

Dear Suhwan,

Using the GATE to CASToR tool, you can use the “-TOF_reso” option in order to enable TOF and set a time resolution corresponding to the CRT.

Regarding scatter and random correction, the tool just computes scatter/random rate according to the acquisition and doesn’t perform real scatter and random corrections. If you want to perform these corrections, you will have to compute them yourself. Alternatively, you can choose to ignore scatter and random and only convert the trues with the -t option.

Hope this helps,
Thibaut

3

Dear Thibaut,

Thank you for your answer.

I will explain in more detail.

So far, I have used the “-TOF_reso” option when simulating a traditional 1-layer crystal detector with a ‘cylindricalPET’.

But the situation is different now.

I tried to perform offset detector image reconstruction with ‘cylindricalPET’, but I found that ‘cylindricalPET’ offset detector could not reconstruct CASTOR images.

Therefore, ‘systemType’ is performing offset detector simulation using ‘PETscanner’. Therefore, I have to make my own cdf and cdh files without using ‘castor-GATERootToCastor’.

Therefore, I checked ‘Table 3’ of CASToR_general_documentation and I am going to try image reconstruction.

But it’s hard for me to understand ‘Table 3’.

I don’t know what data output from ‘GATE Coincidence output’ should be used for scatter correction, random correction and TOF image reconstruction.

I’m sorry I couldn’t tell you the details of the previous question.

If you don’t have enough explanation, please ask me again.

And I would appreciate it if you could let me know if there is any other way other than “PETscanner.”

Thank you. I look forward to hearing from you.

4

Dear Suhwan,

Regarding TOF, the difference in arrival time of the two singles is computed from the time1/time2 variables of the GATE Coincidence root output file. The maximum range of TOF measurements can be approximated by the coincidence window.

Regarding scatter and random corrections, I suggest you have a look at this previous discussion on the matter:

https://lists.castor-project.org/pipermail/castor-users/2020-September/000433.html

About TOF scatter estimation:

https://lists.castor-project.org/pipermail/castor-users/2019-November/000281.html

I would advise to discard scatter/random correction in a first step and only consider the reconstruction of true coincidence data. When you get this right, then focus on including scatter and random corrections.

Best regards,
Thibaut