Hello,
    
after applying hippocampal subfield segmentation to our sample, we noted that summation of hippocampal subfields (in mm3) differs considerably from hippocampal volume (derived from aseg) in some of our subjects:
    
case 1: 2592 mm3 (aseg hipp. volume) versus 2116 mm3 (summation of hipp. subfields)
    
case 2: 4764 mm3 (aseg hipp. volume) versus 4002 mm3 (summation of hipp. subfields)
    
case 3: 1914 mm3 (aseg hipp. volume) versus 2110 mm3 (summation of hipp. subfields) 
    
Please let me know why this is happening, and if this mismatching can be considered normal.
    
Thank you very much in advance.
    
Best regards,
Gabriel