I have converted a series of CT images that were originally DICOM files into NifTI, which I am using to derive intensity values. I have a range of intensity values that I am looking to convert to Hounsfield units. I understand that the linear transformation to convert from intensity to Hounsfield is typically stored in a DICOM header under slope and intercept. However, in the NiFTI file, these header categories are set to NaN (not a number.)
scl_slope : nan
scl_inter : nan
Is there a way to find the slope an intercept from a NifTI file to convert from intensity to Hounsfield units?