TOF reconstruction

General Discussions
1

Dear CASToR developers and users,

I have a question about TOF reconstruction.

I set time resolution 350 (Sqrt(2)* 250 ps in GATE simulation for TOF resolution = 250 ps.

Then I convert root to castor using the following command:

./castor-GATERootToCastor -i /home/pc6/HSPH_CTW350ps.root -m /home/pc6/ PET_Brain.mac -o HSPHCTW350_tof -s BrainPet -geo -TOF_reso 250 -k

The .Cdh is :

Data filename: HSPHCTW350_tof_df.Cdf

Number of events: 35021062

Data mode: list-mode

Data type: PET

Start time (s): 0

Duration (s): 10000

Scanner name: BrainPet1st

Calibration factor: 1

Isotope: unknown

TOF information flag: 1

TOF resolution (ps): 250

List TOF measurement range (ps): 6500

Coincidence kind flag: 1

I reconstruct it with the following command:

./castor-recon -df HSPHCTW350_tof_df.Cdh -dout HoffRecon_CTW350_AC_Tof -atn mumap.hdr -opti MLEM -it 2:10 -th 0 -dim 240,240,184 -fov 268,268,199.4

Reconstructed images of Hoffman phantom with and without TOF resolution are attached.

Is TOF reconstruction applied correctly?

Any help is appreciated

Thanks

Tahereh

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2

Hi Tahereh,
If your detector time resolution is 350ps, your coincidence time resolution must be Sqrt(2)* 350 ps ~ 495ps. From your message it looks like you did the reverse calculation, unless I got it wrong.
Additionally you should compare your reconstructed images for different iterations/subsets levels, as TOF increases convergence of MLEM iterative reconstruction (i.e for the same data you don’t need as many iterations with TOF recon as non-TOF recon).
Hope this helps,
Thibaut

3

Thanks for your response;
Detector time resolution is 250 ps. I set coincidence time resolution= 350 ps in GATE macro.
In ./castor-GATERootToCastor I set -TOF_reso 250.
Is it right? Or I must do reverse calculation?

4

Hi,
For castor-GATERootToCastor, you should give the CTR to TOF-reso, 350ps in your case.
Regarding the GATE macro, it depends on how you set the digitizer (you can provide the DTR or directly the CTR depending on the command).

Best,
Thibaut

5

Thanks for your help.
I correct it.

Best;
Tahereh