Problem of data conversion for Phillips Gemini TF 64

General Discussions
1

Dear Castor users,

I am trying to convert the raw PET data (list-mode) from Phillips Gemini TF 64 to Castor format. Currently, I can read the pair of crystal indexes (transvers and axial) from Gemini data, and then use them to generate the crystal IDs to the corresponding events. I converted the PET data to the Castor formats (both list-mode and histogram) by using the crystal IDs from Gemini. However, I found the orientation difference between castor reconstruction and PET console reconstruction. I have tried to change the “resections first angle” in the geom file to match the rotation, but the castor image is still flipped (left-right and superior-inferior). I am not sure whether this image flip is related to the indexation direction (eg. clock-wise v.s. counter clock-wise) between castor and Gemini. The mismatch orientation between then castor image and CT attenuation map (in Gemini orientation ) makes attenuation correction difficult.

Does anyone know the details of Gemini’s crystal indexation? So, I can convert the crystals IDs to the castor indexation. Or, is it possible to derive the sinogram of attenuation file from scanner (similar to Siemens machines by using e7tools)? or What other options to solve this issue.

I appreciate your help.

Best Regards,

Shenpeng Li, PhD.

CERC Postdoctoral Fellow

Health and Biosecurity, The Australian e-Health Research Centre, CSIRO

343 Royal Parade, Parkville, Victoria 3052, Australia

Dept of Nuclear Medicine and Centre for PET, Austin Hospital

LVL1 Harrold STOKES Block, 145 Studley Road, Heidelberg, Victoria 3084, Australia

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2

Dear Li,

I believe you already tried it, but you could also parameterize the direction of the detector indexation using “rotation direction: CCW” in your geom file (clockwise is default).

Hope this helps,
Thibaut

3

Dear Li,

For the Vereos PET scanner, the detection elements are arranged transversely in the CCW direction and the angular position of the first module with respect to the y-axis is - 80° (see figure).

image.png

If the convention is the same for the Ingenuity, you can try :
rotation direction: CCW
rsectors first angle : -80°.

Hope this helps,

Julien Salvadori

4

Thank you Julien and Thibaut. These are very useful information.

For Gemini TF, the angle seems to be -83.5 (manually tuned and checked visually), but there is translation for all x,y and z axis. I tried to use nbZshift and Zshift to compensate the axial translation (z), but could not fix translation on x,y plane. Any suggestion?

Regards,

Shenpeng

image.png