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The 'orient' field in the data_history structure specifies the primary orientation of the data as it is stored in the file on disk. This usually corresponds to the orientation in the plane of acquisition, given that this would correspond to the order in which the data is written to disk by the scanner or other software application.
It would be vary rare that you would ever encounter any old ANALYZE 7.5 files that contain values of 'orient' which indicate that the data has been 'flipped'. The 'flipped flag' values were really only used internal to the Analyze program to precondition data for fast display in the Movie module, where the images were actually flipped vertically in order to accommodate the raster paint order on older graphics devices. The only cases you will encounter will have values of 0, 1, or 2.
- hdr->orient "MayoClinic/Analyze" Origin dims[1] dims[2] dims[3]
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- 0 transverse-unflipped IRP R->L P->A I->S
- 1 coronal-unflipped IRP R->L I->S P->A
- 2 sagittal-unflipped IRP P->A I->S R->L
- 3 transverse-flipped IRA R->L A->P I->S
- 4 coronal-flipped SRP R->L S->I P->A
- 5 sagittal-flipped ILP P->A I->S L->R
- Where the Origin disignators are with respect to the patient
- [(I)nferior|(S)uperior] [(L}eft|(R)ight] [(A)nterior|(P)osterior]
SPECIAL NOTE: THE BEHAVIOR OF THIS IO ROUTINE DIFFERS FROM THAT OF ANALYZE! NO RE_ORIENTATION OF THE DATA WILL OCCUR IN THE ITK IMPLEMENTATION. Upon loading into the Analyze program, all data is reoriented into the 3D Analyze Coordinate System. The orientation of patient anatomy in the 3D Analyze Coordinate System has a fixed orientation relative to each of the orthogonal axes. This coordinate system does fix the origin in the subject's Inferior-Right-Posterior location relative to anatomy, with a left-handed coordinate system for specification of the other anatomy relative to the axes as given here:
- X-Y plane is Transverse
- X-Z plane is Coronal
- Y-Z plane is Sagittal where:
- X axis runs from patient right (low X) to patient left (high X)
- Y axis runs from posterior (low Y) to anterior (high Y)
- Z axis runs from inferior (low Z) to superior (high Z)
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