TOF Reconstruction ERROR

[Shwan_K]

대용량 첨부파일 2개(1004MB) 대용량 첨부 파일은 30일간 보관 / 100회까지 다운로드 가능

nonTOF.Cdf 430MB

TOF.Cdf 574MB

다운로드 기간: 2022/03/23 ~ 2022/04/22

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Dear CASToR Users and Developers,

Hi I am Suhwan.

I’m having trouble doing TOF reconstruction. I checked the castor manual to make a ‘.Cdf’ file without using the ‘castor-GATERootToCastor’ command. (Table 3)

The non-tof image reconstruction performed well.

However, the image of Tof image reconstruction is strange.

I checked ‘Table 3’ to perform non-tof reconstruction and tof reconstructionf and proceeded with the following procedure.

[non-tof reconstruction]

1. I extracted ‘time’, ‘crystal ID1’, and ‘crystal ID2’ after GATE simulation to proceed with non-tof reconstruction.

2. Using Matlab, ‘time’, ‘crystal ID1’, and ‘crystal ID2’ were combined. And I changed them to ‘uint32’ type.

3. As shown in the picture below, the image of the Phantom came out well.

[tof-reconstruction]

1. For tof reconstruction, ‘time’, ‘crystal ID1’, and ‘crystal ID2’ were extracted after GATE simulation. And to add TOF, the difference between ‘time1’ and ‘time2’ was calculated. ((time2 - time1)*1000000000000)

2. Using Matlab, ‘time’, ‘time2 - time1’, ‘crystal ID1’, and ‘crystal ID2’ were combined. And changed to ‘uint32’ type.

3. And the following text was added to the ‘.Cdh’ file. TOF information flag: 1 TOF resolution (ps): 168.7 List TOF measurement range (ps): 1999.99

4.Tof reconstruction image came out strange as below.

I don’t know what’s wrong.

I have one more question. Why are the corners of the image bright?

Any advice and suggestion will be greatly appreciated. Thank you!

Thanks

nonTOF.Cdh (186 Bytes)

nonTOF.hscan (606 Bytes)

TOF.Cdh (271 Bytes)

TOF.hscan (603 Bytes)

[Maxime_Toussaint]

Greetings,

Maybe I am missing something, but why did you multiply the difference in arrival time by 10^12? GATE TOF data are in ps (if my memory serves me correctly) and CASToR requires TOF data in ps, right?

Bests,
Maxime Toussaint

[Shwan_K]

Dear Maxime Toussaint

Thank you for your reply.

The coincidence output data from GATE is [s]. So I multiplied it by 10^12.

[tmerlin]

Dear Suhwan,

Sorry for the late answer.

There is something wrong in the computation of TOF difference arrival time factors. Their values make no sense (e-43/e-44 ps).

See below the first two events of your file (you can explore further your data file with the castor-datafileExplorer tool, or using some hexadecimal editors).

Regarding the bright corners of the image, the sensitivity at the edges of your image is typically very low and can produce this kind of artifact in various situation, such as:

• No correction of attenuation if it was included in your simulation

• Very low statistics, which can contribute to weird signals.

• No correction of scatter/random coincidences. Signal from these coincidences which may originate from around the phantom could accumulate near the edges of the image.

Hope this helps!

Thibaut Merlin

[Shwan_K]

Dear Thibaut Merlin

Thanks for your reply.

I found out that there was a problem with my file.

Thank you for letting me know about the cause of the artifact.

Thanks