Table 1:
Selective listing of important metadata tags for the conversion process and for DICOM compliance.
| Common Metadata Tags | |
|---|---|
| SOPClassUID | Tells the TPS what type of data is held within the DICOM file. Ex: Values of ‘1.2.840.10008.5.1.4.1.1.2’ and ‘1.2.840.10008.5.1.4.1.1.481.3’ tell software that the written data are CT images or RT-Structure files, respectively. |
| TransferSyntaxUID | The set of encoding rules used during file write-out. In the DICOM-RT Generator, the Explicit VR Little Endian syntax is used (‘1.2.840.10008.1.2.1’), as some TPS require every metadata element to have been explicitly serialized. |
| StudyInstanceUID & SeriesInstanceUID | Unique IDs for the “study” and “series” that the data belong to. Unique IDs are randomly generated in MATLAB using the built-in dicomuid function. |
| SOPInstanceUID | Unique ID for any file. This is used to link organ contours to a particular CT image slice. MATLAB generates a unique SOPInstanceUID during file write-out with the dicomwrite function. |
| FrameOfReferenceUID | Unique ID for the coordinate system for a series of images. By existing within the same Frame of Reference, the TPS knows that images must be spatially related to one another. |
| CT Specific Metadata Tags | |
| Image Position Patient (IPP) | Identifies the coordinates (mm) of the center of the voxel located in the upper-left-hand corner of the image slice. |
| Image Orientation Patient (IOP) | The directional cosines of the image’s rows and columns with respect to the IPP. |
| PixelSpacing | Physical dimensions of the phantom (mm): row spacing (y-dimension), column spacing (x-dimension). |
| SliceThickness | Physical dimension of the phantom (mm) determining the space between image slices (z-dimension). |
| RT-Structure Specific Metadata Tags | |
| StructureSetROISequence | Data structure that contains the order of the organ contours and the names for each contour. |
| RTROIObservationsSequence | Data structure that, for each organ contour, details whether it is an organ contour or external contour. |
| ROIContourSequence | Contains a large structure of organ contour data on each image slice, linked using the SOPInstanceUID. |