[Freesurfer] mri_convert question: converting dicom to mgz

Hello, all. I have not been able to convert dicom files to a mgz file using mri_convert. Could you tell me how to use mri_convert to do that and the example? I typed the following command and run:

mri_convert -it dicom -ot mgz 001/ 001.mgz

Then I got the following message: mri_convert -it dicom -ot mgz 001/ 001.mgz $Id: mri_convert.c,v 1.146.2.5 2009/04/08 18:40:23 nicks Exp $ reading from 001/... Starting DICOMRead2() dcmfile = 001 dcmdir = . ERROR: 001 is not a dicom file

There are 126 dicom files in the directory "001/". OS is CentOS 4.8(64bit), and the version of the Freesurfer I am using is 4.5. Thank you for all your help.

Kenichiro Tanaka.