[Freesurfer] mri_vol2surf puzzle

I posted my question to FSL mailing list, but I guess this forum is more appropriate.

The question is, I have been using mri_vol2surf to convert FSL output into one that is readable by Freesurfer, like the following.

ex) mri_vol2surf --src DPJ/RUN1/djp091306_4_1+.feat/thresh_zstat1.img --src_type analyze --srcreg register.dat --hemi lh --projfrac 0.5 --out DPJ/RUN1/djp091306_4_1+.feat/thresh_zstat1-lh.w --out_type paint

However, in the feat directory via the NEW version of FSL, there is no *.img files (such as thresh_zstat1.img), which mri_vol2surf needs. Instead there are *.nii.gz and *.vol files (such as thresh_zstat1.nii.gz or thresh_zstat1.vol).

Would someone let me know how to go about this problem?

Nam.