1. Abstract metadata for multidimensional image data considered as functions B Gibaud 25/10/2007

2. Goals Provide documentation of the bulk data Concerning – logical organization Range of the function : scalar or not, data type used (uchar, char, int, float, double, etc) Domain of the function : Number of variables, order of variables, number of samples along each dimension, regular sampling or not –Semantics Of components Of variables

3. Spec of domain and range Range (components) –Scalar Data-type, e.g. int32 Semantics, e.g. T1weightedMRIsignalintensity –Vector Nb-components ; table of (Data-type, Semantics) Domain (variables) –Nature of interval Regular-interval –Nb-samples ; inter-sample-distance ; sample-width Non regular interval –Nb-samples ; origin ; table of (dist-to-origin, sample-width ) –Semantics : e.g. space, time, energy

4. Example 1 T1weighted MR dataset –Scalar Range Data-type=int32 Semantics = ‘T1weightedMRsignalintensity’ –3 variables Regular interval –Nb-samples=256, inter_sample-dist=1mm, sample-width=1mm – semantics = ‘space along X’ Regular interval –Nb-samples=256, inter_sample-dist=1mm, sample-width=1mm – semantics = ‘space along Y’ Regular interval –Nb-samples=120, inter_sample-dist= 4mm, sample-width=4mm – semantics = ‘space along Z’

5. Example 2 fMRI dataset –Scalar Range Data-type=int16 Semantics = ‘T2STARMRsignalintensity’ –4 variables Regular interval –Nb-samples=128, inter_sample-dist=4mm, sample-width=4mm – semantics = ‘space along X’ Regular interval –Nb-samples=128, inter_sample-dist=4mm, sample-width=4mm – semantics = ‘space along Y’ Regular interval –Nb-samples=12, inter_sample-dist= 9mm, sample-width=9mm – semantics = ‘space along Z’ Regular interval –Nb-samples=200, inter_sample-dist= 1s, sample-width=0.5s – semantics = ‘time’

6. Example 3 SPECT acquisition dataset (TOMO) –Scalar Range Data-type=int16 Semantics = ‘Number of counts’ –3 variables Regular interval –Nb-samples=128, inter_sample-dist=4mm, sample-width=4mm – semantics = ‘space along X’ Regular interval –Nb-samples=128, inter_sample-dist=4mm, sample-width=4mm – semantics = ‘space along Y’ Regular interval –Nb-samples=128, inter_sample-dist= 2.81°, sample-width=2.81° – semantics = ‘space along theta (projection angle)’

7. Example 4 3D displacement field (non linear registration) –Vector Range 3 components –(Data-type=float ; Semantics = ‘space displacement along X’) –(Data-type=float ; Semantics = ‘space displacement along Y’) –(Data-type=float ; Semantics = ‘space displacement along Z’) –3 variables Regular interval –Nb-samples=256, inter_sample-dist=1mm, sample-width=1mm – semantics = ‘space along X’ Regular interval –Nb-samples=256, inter_sample-dist=1mm, sample-width=1mm – semantics = ‘space along Y’ Regular interval –Nb-samples=120, inter_sample-dist= 4mm, sample-width=4mm – semantics = ‘space along Z’

8. Example 5-1 RGB 2D image –Vector Range 3 components –(Data-type=int16 ; Semantics = ‘Luminance in Red’) –(Data-type=int16 ; Semantics = ‘Luminance in Green’) –(Data-type=int16 ; Semantics = ‘Luminance in Blue’) –2 variables Regular interval –Nb-samples=1024, inter_sample-dist=0.5mm, sample- width=0.5mm – semantics = ‘space along X’ Regular interval –Nb-samples=1024, inter_sample-dist=0.5mm, sample- width=0.5mm – semantics = ‘space along Y’

9. Open issues 1 Need to have a sort of ‘qualitative variable’ to manage e.g. RGB images in 3 separate planes, indexed by this variable ? – semantics of the corresponding variable would be : ‘Red’, ‘Green’, ‘Blue’ ? –semantics of the corresponding (scalar) range would be ‘luminance’ ? Probably needed It would become somewhat arbitrary to choose between a « vector range » versus a colour qualitative variable

10. Example 5-2 RGB 2D image (as 3 separate planes) –Scalar Range (Data-type=int16 ; Semantics = ‘Luminance’) –3 variables Regular interval –Nb-samples=1024, inter_sample-dist=0.5mm, sample-width=0.5mm – semantics = ‘space along X’ Regular interval –Nb-samples=1024, inter_sample-dist=0.5mm, sample-width=0.5mm – semantics = ‘space along Y’ Qualitative variable –Nb-samples=3 –(Semantics = ‘Luminance in Red’) –(Semantics = ‘Luminance in Green’) –(Semantics = ‘Luminance in Blue’)

11. Open issues 2 Need to manage ‘related variables’ ? for instance in the SPECT example (TOMO), the indexing could be done both on the ‘projection angle’ and on ‘time’ –Useful ? –Is sampling necessarily regular with both variables (linear relationship between the two) ?

12. Open issues 3 Need to manage units in which scalar components are represented (Hounsfield, NM units, etc.) ? –Useful ?

13. Example 6 MR Spectro –TBD