I am new to PET and FreeSurfer. I am trying to go through the PetSurfer tutorial (MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be https://surfer.nmr.mgh.harvard.edu/fswiki/PetSurfer). In Part 4 "Register your PET image with the anatomical", the PET data format in example is .nii.gz. However, here are the PET data I have (collected from SIEMENS HRRT PET):

309Fally-309Fally-2021.8.23.11.51.13_EM_frame0_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame0_3D.i.hdr

309Fally-309Fally-2021.8.23.11.51.13_EM_frame1_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame1_3D.i.hdr

309Fally-309Fally-2021.8.23.11.51.13_EM_frame2_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame2_3D.i.hdr

309Fally-309Fally-2021.8.23.11.51.13_EM_frame3_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame3_3D.i.hdr

309Fally-309Fally-2021.8.23.11.51.13_EM_frame4_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame4_3D.i.hdr

309Fally-309Fally-2021.8.23.11.51.13_EM_frame5_3D.i

309Fally-309Fally-2021.8.23.11.51.13_EM_frame5_3D.i.hdr

I tried converting the .i file to (for example) an .nii file by mri_convert but got the following error message:

mri_convert 309Fally-309Fally-2021.8.23.11.51.13_EM_frame0_3D.i 309Fally0.nii

ERROR: cannot determine file type for 309Fally-309Fally-2021.8.23.11.51.13_EM_frame0_3D.i

Then I changed the .i file's extension to .img and the .i.hdr file's extension to .hdr and run mri_convert, but still got an error message:

error: ReadAnalyzeHeader: unsupported data type 17741

I couldn't find anywhere about how to process PET data in .i and .i.hdr files. Any suggestions? I attached one .i.hdr file for your reference.