Clinical MRI systems provide reconstructed images in DICOM format. There exist a range of possibilities for importing DICOM image data into SPM8. Follow the associated link to obtain detailed information about the programs listed below.
 
SPM8 can convert images from DICOM to NIfTI 1.1 format. The conversion process generates a single NIfTI volume for each time point. The individual volumes that constitute the time series can then be concatenated into a 4D NifTI file using the SPM8 "3D to 4D" conversion utility.
 
DCM2NII converts images from DICOM or Philips proprietary MRI scanner formats to the NIfTI 1.1 format. As it is included in the MRIcron distribution, you already have it on your system if you have installed MRIcron.
 
MRIConvert is a medical image file conversion utility that converts DICOM files to NIfTI 1.1
 
The FreeSurfer package includes a DICOM conversion utility called mri_convert that can convert a time series directly from DICOM to the 4D NIfTI format.