You get some rather structural descriptors (number of non-connected parts and their relative organization), and also some descriptors which measure things (length, depth, orientation...).
These versions of the models are the "older" ones but still officially those recommended for sulcal recognition. They are based on what we call "Fold Descriptors 3", which is the version of the descriptors calculation processors. Actually the sulcal recognition use a still older ("Fold Descriptors 2") descriptors system, which is slightly modified and replaced by the "Fold Descriptors 3" for morphometry.
! : None of the measures is currently associated with any thickness (no cortex thickness nor sulcus opening descriptor) because all figures are obtained from sulci segmentation by their skeletonization: segmented data have no thickness (they are systematically 1 voxel thick).
Cortical thickness and more advanced features are now available in the "Fold Descriptor 4"-based models, which are suitable for morphometry, but not yet for recognition: see the folds-models-fd4 models for this.
Here is a short description of the features descriptors:
Notations and names:
Descriptors:
| index: | name: | description: |
| 1. | valid | Global valid flag: 0 if the sulcus is not present, 1 if it is here |
| 2. | extremitiesValid | Validity of the sulcus extremities (more distant points) (0 or 1)) If this is 0, descriptors 3 to 8 are not valid |
| 3. | extremity1x | 1st sulcus extremity (E1). X coordinate |
| 4. | extremity1y | Y coord. |
| 5. | extremity1z | Z coord. |
| 6. | extremity2x | 2nd sulcus extremity (E2). X coord. - E1 and E2 are interchangeable I think... -> it is not really possible to distinguish them a priori (to be verified!) |
| 7. | extremity2y | Y coord. |
| 8. | extremity2z | Z coord. |
| 9. | gravityCenter_x | Gravity center of the sulcus. X coord. |
| 10. | gravityCenter_y | Y coord. |
| 11. | gravityCenter_z | Z coord. |
| 12. | normalValid | Validity of the normal to the sulcus (0 or 1) If this is 0, descriptors 13 to 15 are not valid |
| 13. | normal_x | Mean normal to the sulcus, X coord. |
| 14. | normal_y | Y coord. |
| 15. | normal_z | Z coord. |
| 16. | direction_x | Mean direction of the sulcus, X coord. |
| 17. | direction_y | Y coord. |
| 18. | direction_z | Z coord. |
| 19. | volume | "Size" of the sulcus (volume in mm3 of the skeleton) = # of voxels * voxel volume |
| 20. | geodesicDepthMax | Max. geodesic depth of the sulcus from the external hull |
| 21. | geodesicDepthMin | Min. geodesic depth of the sulcus -> 0 for those touching the brain hull (most of them!), not null in the insula... *** The real depth of the sulcus is Max. depth - min. depth !! *** |
| 22. | connectedComponentsAllRels | Number of connected components (of unconnected parts) in the sulcus, *** according to every kind of intra-sulcus relations !! *** THIS PARAMETER IS CONFUSING.... there are relations across gyri |
| 23. | connectedComponents | Num. of connected components if intra-sulcus "pure cortical" relations (relations across gyri) are not taken into account -> It is THIS parameter that corresponds to the "usual" idea of unconnected sulcus parts |
| 24. | pureCortical | Num. of pure cortical relations linking different connected componentsof the sulcus |
| 25. | distanceBetweenComponentsMax | Max. distance between connected components of the sulcus |
| 26. | plisDePassage | Num. of "plis de passage" inside the sulcus (notable variations of depth or curvature in the bottom of the sulcus), not really reliable because the detection of "plis de passage" is not perfect at all |
| 27. | hullJunctionsSize | Size of junctions between the sulcus and the brain hull -> roughly shows the length of the sulcus |
| 28. | surface | Sulcus surface area. This parameter completes the volume measurement and is not subject to voxel size differences. However this parameter is only available on "recent" sulci graphs, because older ones do not have this parameter. It is possible to add the missing parameter on an old graph using the GraphComplete process. |
| 29. | fold_descriptor3_output | [trained models only] opinion of the expert of the region negative value -> good positive value -> bad *** for untrained models, experts answer at random |
Notations and names:
Descriptors:
| index: | name: | description: |
| 1. | valid | Global valid flag (0 or 1) - 0 if one of the two sulci is not present but 1 if both sulci exist and are not linked by any relation -- Descriptors 2 to 7 briefly describe again each of the 2 sulci, you should better look at their individual descriptors, althrough descriptors 4 and 7 actually give some new and possibly interesting information -- |
| 2. | volumeS1 | Size of S1 |
| 3. | connectedComponentsS1 | Num. of connected components of S1 by non-cortical relations |
| 4. | connectedComponentsS1Rel | Num. of connected components of S1 participating to the relation with S2 |
| 5. | volumeS2 | Size of S2 |
| 6. | connectedComponentsS2 | Num. of connected components of S2 by non-cortical relations |
| 7. | connectedComponentsS2Rel | Num. of connected components of S2 participating to the relation with S1 |
| 8. | corticalSize | Size of cortical relations: length of the border line separating the two sulci (in a Voronoi diagram) -> there is currently no direct information on the gyrus surface... |
| 9. | distanceMin | Minimal distance between the sulci (0 if they are touching) |
| 10. | direction_x | "Global" direction of the relation, X coord. *** be careful, it is sometimes meaningless ! *** |
| 11. | direction_y | Y coord. |
| 12. | direction_z | Z coord. |
| 13. | distanceToExtremity1 | Distance between the contact point on S1 of the relation (point of S1 closest to S2) and the extremity of S1 closest to this point. -> 0 if it is an extremity of S1 that touches S2 or is closest to S2 |
| 14. | distanceToExtremity2 | Distance between the contact point on S2 of the relation (point of S2 closest to S1) and the extremity of S2 closest to this point |
| 15. | gravityCenter_x | Gravity center of the relation, X coord. (rough positioning) |
| 16. | gravityCenter_y | Y coord. |
| 17. | gravityCenter_z | Z coord. |
| 18. | corticalDotProduct | cosinus of the angle between the global directions of S1 and S2 (scalar product of the directions) |
| 19. | junctions | Num. of junctions between the two sulci *** this does not necessarily show the number of places they are touching *** |
| 20. | junctionDepthMin | Minimal depth of the junctions: non-null only if the sulci only touch on a deep "pli de passage" |
| 21. | junctionsSize | Size (length) of the junctions between the two sulci |
| 22. | plisDePassage | Num. of "plis de passage" joining the two sulci |
| 23. | plisDePassageDepthMax | Max. depth of "plis de passage" |
| 24. | inter_fold_descriptor2_output | [trained models only] output of this relation expert, as for sulci, negative values are good, positive are bad |
For more detailed information, see the PhD thesis of D. Rivière (in french)