Thanks for your so quick reply,now I changed the VOI name as".nii" format, it works!
But I encountered another question, reported as follow:
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VOI has 925 voxels in 2x2x2 space

VOI has 272 voxels in 3x3x3 space. This is in the the same space as the input data and functional mask.
Retrieval Positive does not exist. Program will exit
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The condition"Retrieval Positive" exited indeed, I am confused about that.
Could you please help me again!
Thanks in advance!!
Best,
Xinyuan