On most (all?) scanners TR is stored as an integer. For example, on siemens it's in microseconds and then stored as a long. (this is the value in the protocol, not the actual execution TR, but when/if there are no bugs, then this is correct). When you convert a long to float (single or double precision) you will get some junk in the low bits because of type conversion. In the dicom it's all string representations.
Does the dicom say 50.000 or 50? How does the conversion from int -- Souheil Inati, PhD Staff Scientist Functional MRI Facility NIMH/NIH/DHHS souheil.in...@nih.gov On Aug 28, 2012, at 12:06 PM, Bruce Fischl wrote: > does NIFTI support the MR parameters? I'm not sure it does. I suspect > that 50 is correct and not 50.000000745058060 (can you imagine setting > that on the console)? > On Tue, 28 Aug 2012, dgw wrote: > >> Hi, >> >> I'm not sure if this is a bug report or a feature request. I have been >> using mri_convert to convert dicoms to nii.gz and mgz files, and I >> have noticed some discrepancies when reading the volumes in with >> MRIread in either matlab or octave. The volumes differ in their >> support of the flip angle, tr, te, and ti fields (I realize some of >> this may be due to file type differences). Thought the standard output >> of mri_convert shows the expected values. >> >> In the mgz file the TR seems to be rounded i.e. >> 50 instead of 50.000000745058060 in the nii.gz >> >> In the mgz file the flip angle and te are recorded >> FA 0.52.... while in the nii.gz it is 0 >> te 10.39... while in the nii.gz it is 0 >> >> The ti value appears strange to me in the mgz >> ti = -1 while in the nii.gz it is 0 >> >> I have generated two files using mri convert off of the same MR volume >> as a test case: >> /cluster/hbot/agario_p2_2/dcm/020_t1_fl2d_tra_TEMP/004/877000-000020-000003.dcm >> >> /cluster/hbot/agario_p2_2/dcm/020_t1_fl2d_tra_TEMP/004/volume.nii.gz >> >> /cluster/hbot/agario_p2_2/dcm/test.mgz >> >> These files were generated using /usr/local/freesurfer/stable5_1_0/ >> >> Thanks, >> D >> _______________________________________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >> >> >> > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > The information in this e-mail is intended only for the person to whom it is > addressed. If you believe this e-mail was sent to you in error and the e-mail > contains patient information, please contact the Partners Compliance HelpLine > at > http://www.partners.org/complianceline . If the e-mail was sent to you in > error > but does not contain patient information, please contact the sender and > properly > dispose of the e-mail. > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
